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Alkynes: From Reaction Design to Applications in Organic Synthesis
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Alkynes: From Reaction Design to Applications in Organic Synthesis

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (30 January 2019) | Viewed by 84446

Special Issue Editor

Prof. Dr. Igor Alabugin

E-Mail Website
Guest Editor
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA
Interests: organic reaction mechanisms; stereoelectronic effects; organic photochemistry; DNA photocleavage; carbon-rich materials; chemistry of alkynes; radical chemistry; cyclizations; cycloaromatizations; electron upconversion; hole catalysis; high energy functional groups
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Alkyne functionality represents one of the most valuable building blocks of organic chemistry. Despite its seeming simplicity, it combines many unusual and attractive features. For example, the compact carbon-rich alkyne moiety stores >60 kcal/mol of potential energy. Furthermore, alkynes have the same oxidation state as carbonyl compounds and, hence, via simple addition of nucleophiles, offer a “hidden door” entry into carbonyl chemistry. Due to the presence of two independently addressable π-systems, alkynes can readily form four (and, under certain conditions, up to six) new bonds, lending themselves perfectly to the design of cascade transformations. The recent examples of unusual alkyne transformations include ionic chemistry of neutral hydrocarbons, preparation of radicals without radical initiators, generation of excited states without light, "1,2-dicarbene reactivity" of alkynes in "boomerang" radical processes, selective conversion of alkynes into carbonyl compounds, and full disassembly of the alkyne moiety. With the advent of modern catalytic methods, it seems that new reactions of alkynes are discovered every day.

Recognizing the hidden connections between the fundamental features of alkynes and their rich reactivity is essential for uncovering the full potential of this functionality in organic synthesis. The goal of this Special Issue to is to bring multiple examples of new alkyne reactions under one cover to catalyze cross-pollination of ideas for the future development of alkyne chemistry. This issue will contain contributions that cover all aspects of alkyne structure, reactivity, and applications in organic synthesis.

Prof. Dr. Igor V. Alabugin
Guest Editor

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Keywords

  • alkynes
  • cascade transformations
  • catalysis
  • addition

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Published Papers (11 papers)

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Research

Jump to: Review

26 pages, 10153 KiB  
Article
Ring Expansion of Alkylidenecarbenes Derived from Lactams, Lactones, and Thiolactones into Strained Heterocyclic Alkynes: A Theoretical Study
by Nguyen Nhat Thu Le, Josefine Just, Jonathan M. Pankauski, Paul R. Rablen and Dasan M. Thamattoor
Molecules 2019, 24(3), 593; https://doi.org/10.3390/molecules24030593 - 7 Feb 2019
Cited by 3 | Viewed by 3604
Abstract
Strained cycloalkynes are of considerable interest to theoreticians and experimentalists, and possess much synthetic value as well. Herein, a series of cyclic alkylidenecarbenes—formally obtained by replacing the carbonyl oxygen of four-, five-, and six-membered lactams, lactones, and thiolactones with a divalent carbon—were modeled [...] Read more.
Strained cycloalkynes are of considerable interest to theoreticians and experimentalists, and possess much synthetic value as well. Herein, a series of cyclic alkylidenecarbenes—formally obtained by replacing the carbonyl oxygen of four-, five-, and six-membered lactams, lactones, and thiolactones with a divalent carbon—were modeled at the CCSD(T)/cc-pVTZ//B3LYP/6-311+G** and CCSD(T)/cc-pVTZ//CCSD/6-311+G** levels of theory. The singlet carbenes were found to be more stable than the triplets. The strained heterocyclic alkynes formed by ring expansion of these singlet carbenes were also modeled. Interestingly, the C≡C bonds in the five-membered heterocycles, obtained from the rearrangement of β-lactam- and β-lactone-derived alkylidenecarbenes, displayed lengths intermediate between formal double and triple bonds. Furthermore, 2-(1-azacyclobutylidene)carbene was found to be nearly isoenergetic with its ring-expanded isomer, and 1-oxacyclopent-2-yne was notably higher in energy than its precursor carbene. In all other cases, the cycloalkynes were lower in energy than the corresponding carbenes. The transition states for ring-expansion were always lower for the 1,2-carbon shifts than for 1,2-nitrogen or oxygen shifts, but higher than for the 1,2-sulfur shifts. These predictions should be verifiable using carbenes bearing appropriate isotopic labels. Computed vibrational spectra for the carbenes, and their ring-expanded isomers, are presented and could be of value to matrix isolation experiments. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>12</b>, and the PES for the conversion of singlet <b>12</b> into 1-azacyclopent-2-yne (<b>13</b>) by two different pathways.</p> Full article ">Figure 2
<p>Resonance contributions in <b>12</b> showing a C=N bond in the zwitterionic form.</p> Full article ">Figure 3
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>12</b> (bottom), triplet <b>12</b> (middle), and <b>13</b> (top).</p> Full article ">Figure 4
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>13</b>, and the PES for the conversion of singlet <b>14</b> into 1-oxacyclopent-2-yne (<b>15</b>) by two different pathways.</p> Full article ">Figure 5
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>14</b> (bottom), triplet <b>14</b> (middle), and <b>15</b> (top).</p> Full article ">Figure 6
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>15</b>, and the PES for the conversion of singlet <b>16</b> into 1-thiocyclopent-2-yne (<b>17</b>) by two different pathways.</p> Full article ">Figure 7
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>16</b> (bottom), triplet <b>16</b> (middle), and <b>17</b> (top).</p> Full article ">Figure 8
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>18</b>, and the PES for the conversion of singlet <b>18</b> into 1-azacyclohex-2-yne (<b>19</b>) by two different pathways.</p> Full article ">Figure 9
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>18</b> (bottom), triplet <b>18</b> (middle), and <b>19</b> (top).</p> Full article ">Figure 10
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>20</b>, and the PES for the conversion of singlet <b>20</b> into 1-oxacyclohex-2-yne (<b>21</b>) by two different pathways.</p> Full article ">Figure 11
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>20</b> (bottom), triplet <b>20</b> (middle), and <b>21</b> (top).</p> Full article ">Figure 12
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>22</b>, and the PES for the conversion of singlet <b>22</b> into 1-thiocyclohex-2-yne (<b>23</b>) by two different pathways.</p> Full article ">Figure 13
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>22</b> (bottom), triplet <b>22</b> (middle), and <b>23</b> (top).</p> Full article ">Figure 14
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>24</b>, and the PES for the conversion of singlet <b>24</b> into 1-azacyclohept-2-yne (<b>25</b>) by two different pathways.</p> Full article ">Figure 15
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>24</b> (bottom), triplet <b>24</b> (middle), and <b>25</b> (top).</p> Full article ">Figure 16
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>26</b>, and the PES for the conversion of singlet <b>26</b> into 1-oxacyclohept-2-yne (<b>27</b>) by two different pathways.</p> Full article ">Figure 17
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>26</b> (bottom), triplet <b>26</b> (middle), and <b>27</b> (top).</p> Full article ">Figure 18
<p>CCSD(T)/cc-pVTZ//CCSD/6-311+G** structures and energies of singlet and triplet <b>28</b>, and the PES for the conversion of singlet <b>28</b> into 1-thiocyclohept-2-yne (<b>29</b>) by two different pathways.</p> Full article ">Figure 19
<p>Vibrational spectra computed at CCSD/6-311+G** for singlet <b>28</b> (bottom), triplet <b>28</b> (middle), and <b>29</b> (top).</p> Full article ">Figure 20
<p>Summary of results depicting preferred rearrangement modes for the alkylidenecarbenes discussed in this study.</p> Full article ">Figure 21
<p>Carbenes studied by Robson and Shechter [<a href="#B64-molecules-24-00593" class="html-bibr">64</a>] to probe migratory aptitudes of substituents at the β-position.</p> Full article ">Scheme 1
<p>(<b>a</b>) The ring expansion of alkylidene carbenes and carbenoids to linear alkynes. R<sup>1</sup> and R<sup>2</sup> may be the same or different. M is a metal and X a leaving group. (<b>b</b>) An analogous approach to the generation of cycloalkynes from cyclic alkylidenecarbenes and carbenoids.</p> Full article ">Scheme 2
<p>Phenanthrene-based methylenecyclopropanes, exemplified by <b>7</b> and <b>8</b>, can be used as photochemical sources of acyclic and cyclic alkylidenecarbenes respectively.</p> Full article ">Scheme 3
<p>The ring expansion of alkylidenecarbenes (<b>10</b>), derived from lactams, lactones, and thiolactones (<b>9</b>), into strained heterocyclic compounds (<b>11</b>).</p> Full article ">Scheme 4
<p>Two pathways for the ring expansion of singlet alkylidenecarbenes derived from β-lactam, β-lactone, and β-thiolactone.</p> Full article ">Scheme 5
<p>Ring expansion of singlet alkylidenecarbenes, derived from γ-lactam, γ-lactone, and γ-thiolactone, by a 1,2 shift of either X or carbon.</p> Full article ">Scheme 6
<p>Ring expansion of singlet alkylidenecarbenes, derived from δ-lactam, δ-lactone, and δ-thiolactone, by a 1,2 shift of either X or carbon.</p> Full article ">
21 pages, 33303 KiB  
Article
TfOH-Promoted Reaction of 2,4-Diaryl-1,1,1-Trifluorobut-3-yn-2-oles with Arenes: Synthesis of 1,3-Diaryl-1-CF3-Indenes and Versatility of the Reaction Mechanisms
by Aleksey V. Zerov, Anna N. Kazakova, Irina A. Boyarskaya, Taras L. Panikorovskii, Vitalii V. Suslonov, Olesya V. Khoroshilova and Aleksander V. Vasilyev
Molecules 2018, 23(12), 3079; https://doi.org/10.3390/molecules23123079 - 25 Nov 2018
Cited by 11 | Viewed by 4609
Abstract
The TfOH-mediated reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-substituted diaryl propargyl alcohols) with arenes in CH2Cl2 afford 1,3-diaryl-1-CF3-indenes in yields up to 84%. This new process for synthesis of such CF3-indenes is complete at room temperature within [...] Read more.
The TfOH-mediated reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-substituted diaryl propargyl alcohols) with arenes in CH2Cl2 afford 1,3-diaryl-1-CF3-indenes in yields up to 84%. This new process for synthesis of such CF3-indenes is complete at room temperature within one hour. The synthetic potential, scope, and limitations of this reaction were illustrated by more than 70 examples. The proposed reaction mechanism invokes the formation of highly reactive CF3-propargyl cation intermediates that can be trapped at the two mesomeric positions by the intermolecular nucleophilic attack of an arene partner with a subsequent intramolecular ring closure. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Starting CF<sub>3</sub>-propargyl alcohols used in this study.</p> Full article ">Figure 2
<p>X-ray crystal structures of compounds <b>4bg</b> (CCDC 1568593), <b>4ci</b> (CCDC 1578216), <b>4dc</b> (CCDC 1568602), <b>4de</b> (CCDC 1568599), <b>4dg</b> (CCDC 1568594), <b>4di</b> (CCDC 1563374), <b>4dk</b> (CCDC 1568596), <b>4dm</b> (CCDC 1568600), <b>4fb</b> (CCDC 1568595), <b>4fc</b> (CCDC 1568597), <b>4fh</b> (CCDC 1568603), <b>4fk</b> (CCDC 1568598), and <b>5ac</b> (CCDC 1568601) (ellipsoid contour of probability levels is 50%), Green sticks are fluorine atoms.</p> Full article ">Figure 2 Cont.
<p>X-ray crystal structures of compounds <b>4bg</b> (CCDC 1568593), <b>4ci</b> (CCDC 1578216), <b>4dc</b> (CCDC 1568602), <b>4de</b> (CCDC 1568599), <b>4dg</b> (CCDC 1568594), <b>4di</b> (CCDC 1563374), <b>4dk</b> (CCDC 1568596), <b>4dm</b> (CCDC 1568600), <b>4fb</b> (CCDC 1568595), <b>4fc</b> (CCDC 1568597), <b>4fh</b> (CCDC 1568603), <b>4fk</b> (CCDC 1568598), and <b>5ac</b> (CCDC 1568601) (ellipsoid contour of probability levels is 50%), Green sticks are fluorine atoms.</p> Full article ">Scheme 1
<p>Plausible mechanisms of acid-promoted reactions of CF<sub>3</sub>-alcohols <b>1</b> with arenes.</p> Full article ">Scheme 2
<p>TfOH-promoted reaction of <b>1</b> with <span class="html-italic">o</span>-xylene in TfOH; reaction conditions: TfOH, CH<sub>2</sub>Cl<sub>2</sub>, molar ratio of <b>1</b>:benzene:TfOH = 1:1.1:1.5, room temperature, 1 h.</p> Full article ">Scheme 3
<p>TfOH-promoted reaction of <b>1n</b> with <span class="html-italic">p</span>-xylene in TfOH.</p> Full article ">
12 pages, 2832 KiB  
Article
Synthesis of Carvone-Derived 1,2,3-Triazoles Study of Their Antioxidant Properties and Interaction with Bovine Serum Albumin
by Armen S. Galstyan, Armen I. Martiryan, Karine R. Grigoryan, Armine G. Ghazaryan, Melanya A. Samvelyan, Tariel V. Ghochikyan and Valentine G. Nenajdenko
Molecules 2018, 23(11), 2991; https://doi.org/10.3390/molecules23112991 - 16 Nov 2018
Cited by 18 | Viewed by 4436
Abstract
Natural L-carvone was utilized as a starting material for an efficient synthesis of some terpenyl-derived 1,2,3-triazoles. Chlorination of carvone, followed by nucleophilic substitution with sodium azide resulted in the preparation of 10-azidocarvone. Subsequent CuAAC click reaction with propargylated derivatives provided an efficient synthetic [...] Read more.
Natural L-carvone was utilized as a starting material for an efficient synthesis of some terpenyl-derived 1,2,3-triazoles. Chlorination of carvone, followed by nucleophilic substitution with sodium azide resulted in the preparation of 10-azidocarvone. Subsequent CuAAC click reaction with propargylated derivatives provided an efficient synthetic route to a set of terpenyl-derived conjugates with increased solubility in water. All investigated compounds exhibit high antioxidant activity, which is comparable with that of vitamin C. It was also found that serum albumin and the terpenyl-1,2,3-triazoles hybrids spontaneously undergo reversible binding driven by hydrophobic interactions, suggesting that serum albumin can transport the target triazoles. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
►▼ Show Figures

Figure 1

Figure 1
<p>Structures of artemisinin and Taxol<sup>®</sup>.</p> Full article ">Figure 2
<p>Some menthane-derived monoterpenoids.</p> Full article ">Figure 3
<p>Some triazole-derived drugs.</p> Full article ">Figure 4
<p>(<b>a</b>) compound <b>4a</b>; (<b>b</b>) compound <b>4b</b>; (<b>c</b>) compound <b>4c</b>; (<b>d</b>) compound <b>4d</b>; (<b>e</b>) compound <b>4e</b>. Dependence of optical density of PNDMA vs the time of UV irradiation (λ = 313 nm) at various concentrations of compounds <b>4a</b>–<b>e</b>; (<b>f</b>) dependence of rate of PNDMA discoloring (in units) vs the concentration: compounds <b>4а</b>–<b>e</b>.</p> Full article ">Scheme 1
<p><span class="html-italic">Reagen</span><span class="html-italic">ts and conditions</span>: <span class="html-italic">i</span>–Ca(OCl)<sub>2</sub>, CO<sub>2</sub>, DCM/H<sub>2</sub>O, 0 °C; <span class="html-italic">ii</span>—NaN<sub>3</sub>, MeCN or DMSO; <span class="html-italic">iii</span>—3-bromoprop-1-yne, EtOH or MeCN, base; <span class="html-italic">iv</span>—Et<sub>3</sub>N, CuBr or CuI (5 mol%), MeCN or DMSO, 60 °C.</p> Full article ">
7 pages, 654 KiB  
Article
Synthesis of Acridines through Alkyne Addition to Diarylamines
by Kristen E. Berger, Grant M. McCormick, Joseph A. Jaye, Christina M. Rozeske and Eric H. Fort
Molecules 2018, 23(11), 2867; https://doi.org/10.3390/molecules23112867 - 3 Nov 2018
Cited by 8 | Viewed by 4362
Abstract
A new synthesis of substituted acridines is achieved by palladium-catalyzed addition of terminal acetylenes between the aryl rings of bis(2-bromophenyl)amine. By including a diamine base and elevating the temperature, the reaction pathway favors the formation of acridine over a double Sonogashira reaction to [...] Read more.
A new synthesis of substituted acridines is achieved by palladium-catalyzed addition of terminal acetylenes between the aryl rings of bis(2-bromophenyl)amine. By including a diamine base and elevating the temperature, the reaction pathway favors the formation of acridine over a double Sonogashira reaction to form bis(tolan)amine. This method is demonstrated with several aryl-alkynes and alkyl-alkynes. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Cross-coupling reactions to produce precursor <b>3</b> and bis(tolan)amine (<b>4a</b>) [<a href="#B34-molecules-23-02867" class="html-bibr">34</a>,<a href="#B35-molecules-23-02867" class="html-bibr">35</a>].</p> Full article ">Scheme 1
<p>Proposed pathway for acridine formation. Catalytic cycles abbreviated for clarity.</p> Full article ">
7 pages, 1277 KiB  
Communication
Highly Efficient Recyclable Sol Gel Polymer Catalyzed One Pot Difunctionalization of Alkynes
by Justin Domena, Carlos Chong, Qiaxian R. Johnson, Bhanu P. S. Chauhan and Yalan Xing
Molecules 2018, 23(8), 1879; https://doi.org/10.3390/molecules23081879 - 27 Jul 2018
Cited by 2 | Viewed by 3927
Abstract
Amino-bridged gel polymer P1 was discovered to catalyze alkyne halo-functionalization in excellent yields, regioselectivity, functional group compatibility, and recyclability. We have observed that both aromatic and aliphatic alkynes can be converted to α,α-dihalogenated ketones in the presence of polymer P1 under metal-free conditions [...] Read more.
Amino-bridged gel polymer P1 was discovered to catalyze alkyne halo-functionalization in excellent yields, regioselectivity, functional group compatibility, and recyclability. We have observed that both aromatic and aliphatic alkynes can be converted to α,α-dihalogenated ketones in the presence of polymer P1 under metal-free conditions at room temperature within a short reaction time. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Solid state <sup>13</sup>C-NMR of the amino-bridged gel <b>P1</b>.</p> Full article ">Figure 2
<p>Substrate scope with isolated yields.</p> Full article ">Figure 3
<p>Recyclability studies.</p> Full article ">Scheme 1
<p>(<b>1A</b>) Alkyne difunctionalization and (<b>1B</b>) alkyne difunctionalization catalyzed by polymer gel.</p> Full article ">Scheme 2
<p>Synthetic strategy to amino-bridged gels.</p> Full article ">
11 pages, 1804 KiB  
Article
Vinylation of a Secondary Amine Core with Calcium Carbide for Efficient Post-Modification and Access to Polymeric Materials
by Konstantin S. Rodygin, Alexander S. Bogachenkov and Valentine P. Ananikov
Molecules 2018, 23(3), 648; https://doi.org/10.3390/molecules23030648 - 13 Mar 2018
Cited by 35 | Viewed by 8028
Abstract
We developed a simple and efficient strategy to access N-vinyl secondary amines of various naturally occurring materials using readily available solid acetylene reagents (calcium carbide, KF, and KOH). Pyrrole, pyrazole, indoles, carbazoles, and diarylamines were successfully vinylated in good yields. Cross-linked and [...] Read more.
We developed a simple and efficient strategy to access N-vinyl secondary amines of various naturally occurring materials using readily available solid acetylene reagents (calcium carbide, KF, and KOH). Pyrrole, pyrazole, indoles, carbazoles, and diarylamines were successfully vinylated in good yields. Cross-linked and linear polymers were synthesized from N-vinyl carbazoles through free radical and cationic polymerization. Post-modification of olanzapine (an antipsychotic drug substance) was successfully performed. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Scheme 1
<p>Synthetic procedures to access <span class="html-italic">N</span>-vinyl derivatives.</p> Full article ">Scheme 2
<p>Plausible mechanism of vinylation of secondary amines.</p> Full article ">Scheme 3
<p>Structures of vinylated secondary amine products and yields (in %). Reaction conditions: amine <b>1</b> (1 mmol), CaC<sub>2</sub> (2 mmol), KOH (1.1 mmol), KF (1 mmol), H<sub>2</sub>O (4 mmol), DMSO (1 mL). NMR yields are given without parentheses, isolated yields are given in parentheses.</p> Full article ">Scheme 4
<p><span class="html-italic">N</span>-vinyl-1,2,3,4-tetrahydrocarbazole synthesis and polymerization.</p> Full article ">Scheme 5
<p>Double vinylation followed by the polymerization of bis(<span class="html-italic">N</span>-vinyl-3,3′-carbazole) and the X-ray structure of <b>2m</b>.</p> Full article ">Scheme 6
<p>Vinylation of olanzapine and X-ray structure of the vinylated olanzapine derivative.</p> Full article ">

Review

Jump to: Research

36 pages, 10545 KiB  
Review
Alkynes as Synthetic Equivalents of Ketones and Aldehydes: A Hidden Entry into Carbonyl Chemistry
by Igor V. Alabugin, Edgar Gonzalez-Rodriguez, Rahul Kisan Kawade, Aleksandr A. Stepanov and Sergei F. Vasilevsky
Molecules 2019, 24(6), 1036; https://doi.org/10.3390/molecules24061036 - 15 Mar 2019
Cited by 53 | Viewed by 10319
Abstract
The high energy packed in alkyne functional group makes alkyne reactions highly thermodynamically favorable and generally irreversible. Furthermore, the presence of two orthogonal π-bonds that can be manipulated separately enables flexible synthetic cascades stemming from alkynes. Behind these “obvious” traits, there are other [...] Read more.
The high energy packed in alkyne functional group makes alkyne reactions highly thermodynamically favorable and generally irreversible. Furthermore, the presence of two orthogonal π-bonds that can be manipulated separately enables flexible synthetic cascades stemming from alkynes. Behind these “obvious” traits, there are other more subtle, often concealed aspects of this functional group’s appeal. This review is focused on yet another interesting but underappreciated alkyne feature: the fact that the CC alkyne unit has the same oxidation state as the -CH2C(O)- unit of a typical carbonyl compound. Thus, “classic carbonyl chemistry” can be accessed through alkynes, and new transformations can be engineered by unmasking the hidden carbonyl nature of alkynes. The goal of this review is to illustrate the advantages of using alkynes as an entry point to carbonyl reactions while highlighting reports from the literature where, sometimes without full appreciation, the concept of using alkynes as a hidden entry into carbonyl chemistry has been applied. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Scheme 1

Scheme 1
<p>Markovnikov (top) and anti-Markovnikov (bottom) hydration of alkynes converts them into either ketones or aldehydes, respectively.</p> Full article ">Scheme 2
<p>Synthetic equivalency of alkynes and carbonyl compounds.</p> Full article ">Scheme 3
<p>Thermodynamics of enol and enamine formation from an alkyne and a ketone.</p> Full article ">Scheme 4
<p>Each alkyne opens not one but two doors into carbonyl chemistry.</p> Full article ">Scheme 5
<p>Synthesis of α-arylphenones and α,α-diarylketones through directed catalytic alkyne arylations.</p> Full article ">Scheme 6
<p>Comparison of alkynes and carbonyls as precursors for vinyl ethers.</p> Full article ">Scheme 7
<p>Comparison of alkynes and ketones in intramolecular spiro-ketalizations.</p> Full article ">Scheme 8
<p>Utimoto’s Au-catalized acetal formation from alkyne starting materials.</p> Full article ">Scheme 9
<p>Dudley’s intramolecular bishydroxylation of alkynes.</p> Full article ">Scheme 10
<p>Gold catalyzed bis-alkoxylation of alkynes in the synthesis of spiroketals by Forsyth and coworkers.</p> Full article ">Scheme 11
<p>Thermodynamics of hemiacetal/vinyl ether transformation can be unfavorable.</p> Full article ">Scheme 12
<p>Top: Two patterns (C-enolexo and C-enolendo) for exo-tet cyclizations. Bottom: Although cyclizations of enolates can occur at either the carbon or oxygen, this process is controlled by stereoelectronic factors (see discussion in text).</p> Full article ">Scheme 13
<p>Approaches to selective exo-dig and endo-dig cyclizations can be accomplished by using either a classic anionic or a Lewis acid-mediated (the so-called “Electrophile-Promoted Nucleophilic Closure (EPNC) processes) pathways with different stereoelectronic requirements.</p> Full article ">Scheme 14
<p>Potential energy surfaces for selected exo-dig and endo-dig anionic cyclizations of <span class="html-italic">N</span>- (blue dashed, <span class="html-italic">italic</span>) and <span class="html-italic">O</span>- (violet dashed, non-italics) anions with terminal alkynes.</p> Full article ">Scheme 15
<p>Two approaches to regioselective alkyne/carbonyl transformations.</p> Full article ">Scheme 16
<p>Base promoted 5-exo-dig cyclizations of primary and secondary alcohols onto terminal triple bonds.</p> Full article ">Scheme 17
<p>The solvent dependent cyclizations of oxygen anions with three sp<sup>2</sup>-atoms in the linking chain.</p> Full article ">Scheme 18
<p><span class="html-italic">Top:</span> The cyclization of o-carboxy acetylenes, formed via cuprate addition, prefers the 5-exo-dig pathway. <span class="html-italic">Bottom:</span> Regioselective 6-endo-dig cyclizations of acetylenic carboxylates at five-membered rings.</p> Full article ">Scheme 19
<p>Control of <span class="html-italic">N</span>-nucleophilic closures by changing alkyne electronics.</p> Full article ">Scheme 20
<p>Diverging mechanistic pathways in reactions of peri-substituted acetylenyl-9,10-anthraquinones and guanidine.</p> Full article ">Scheme 21
<p>Reductive dimerization of ethynyl anthraquinones.</p> Full article ">Scheme 22
<p>“The LUMO Umpolung”: coordination of a Lewis acid at the alkyne changes the LUMO symmetry and deactivates a destabilizing secondary orbital interaction that disfavors endo-dig cyclizations.</p> Full article ">Scheme 23
<p>The formal “all-endo” metal-assisted cyclization cascade is initiated by a 5-endo-dig closure followed by two 6-endo-dig closures.</p> Full article ">Scheme 24
<p>Cycloisomerizations of terminal alkynols under Ru-catalysis.</p> Full article ">Scheme 25
<p>Two possible stabilization patterns for the Petasis-Ferrier rearrangement.</p> Full article ">Scheme 26
<p>Au-catalyzed versions of the Petasis-Ferrier reaction. Top: cation stabilization by an endocyclic donor assists transformation of homopropargylic esters and amides into heterocyclic products. Bottom: cation stabilization by an exocyclic donor assists transformation of <span class="html-italic">ortho</span>-alkynyl benzyl methyl ethers into naphthalenes.</p> Full article ">Scheme 27
<p>1,2-shifts in the Baeyer-Villiger and aza-Baeyer-Villiger reactions.</p> Full article ">Scheme 28
<p>Alkyne “disassembly” via carbonyl cascades leading to nitrogen insertion between alkyne carbons. Note that the fragmentation−recyclization sequence is analogous to the Petasis−Ferrier rearrangement whereas the [1,2]-shift can be considered as an aza-analogue of the Baeyer-Villiger reaction.</p> Full article ">Scheme 29
<p>Synthesis of cyclic enones from dicarbonyls and diynes.</p> Full article ">Scheme 30
<p>Use of alkynes as enolate equivalents in the formal aldol condensations with aldehydes (“alkyne-carbonyl metathesis”).</p> Full article ">Scheme 31
<p>Suggested mechanism of the alkyne-carbonyl “aldol condensations”.</p> Full article ">Scheme 32
<p>Au-catalyzed hydrative cyclizations of diynes.</p> Full article ">Scheme 33
<p>Ruthenium catalyzed hydrative cyclization of diynes.</p> Full article ">Scheme 34
<p>Use of alkyne high energy and cross-over to the “carbonyl reaction field” for the full disassembly of triple bond.</p> Full article ">Scheme 35
<p>Complete scission of the triple bond in keto alkynes mediated by the retro-Mannich reaction.</p> Full article ">Scheme 36
<p>Variations of retro-Mannich-mediated alkyne fragmentations with the 2nd nucleophilic attack being <span class="html-italic">inter</span>molecular.</p> Full article ">Scheme 37
<p>Reaction of <span class="html-italic">α</span>-alkynylketones with aminoalcohols.</p> Full article ">Scheme 38
<p>Reaction of α-ketoacetylenes with pseudoephedrine.</p> Full article ">Scheme 39
<p>C≡C bond scission in 1- and 2-phenylethynyl-9,10-anthraquinones.</p> Full article ">Scheme 40
<p>Expanded alkyne fragmentation reactions to compounds containing varied functionalities.</p> Full article ">Scheme 41
<p>Alkyne fragmentation reactions in pyridine containing substrates.</p> Full article ">Scheme 42
<p>Retrosynthetic equivalency of alkynes and methyl group (top) and protected carboxylic acids (bottom).</p> Full article ">Scheme 43
<p>Reaction of CF<sub>3</sub>-ynones with amino alcohols.</p> Full article ">Scheme 44
<p>Retrosynthetic analysis of two potential routes to metal-carbenes from alkynes and ketones.</p> Full article ">Scheme 45
<p>α-Oxo gold carbenes via Au-catalyzed alkyne oxidation.</p> Full article ">Scheme 46
<p>Palladium and Gold catalyzed cycloisomerizations of 1-ethynyl-2-propenyl acetates to 2-cyclopentenones.</p> Full article ">Scheme 47
<p>Insertion of cyclobutene ring between two carbonyl carbons via pericyclic chemistry of alkynes.</p> Full article ">
56 pages, 13754 KiB  
Review
Preparation and Utility of N-Alkynyl Azoles in Synthesis
by Brandon Reinus and Sean M. Kerwin
Molecules 2019, 24(3), 422; https://doi.org/10.3390/molecules24030422 - 24 Jan 2019
Cited by 8 | Viewed by 6375
Abstract
Heteroatom-substituted alkynes have attracted a significant amount of interest in the synthetic community due to the polarized nature of these alkynes and their utility in a wide range of reactions. One specific class of heteroatom-substituted alkynes combines this utility with the presence of [...] Read more.
Heteroatom-substituted alkynes have attracted a significant amount of interest in the synthetic community due to the polarized nature of these alkynes and their utility in a wide range of reactions. One specific class of heteroatom-substituted alkynes combines this utility with the presence of an azole moiety. These N-alkynyl azoles have been known for nearly 50 years, but recently there has been a tremendous increase in the number of reports detailing the synthesis and utility of this class of compound. While much of the chemistry of N-alkynyl azoles mirrors that of the more extensively studied N-alkynyl amides (ynamides), there are notable exceptions. In addition, as azoles are extremely common in natural products and pharmaceuticals, these N-alkynyl azoles have high potential for accessing biologically important compounds. In this review, the literature reports of N-alkynyl azole synthesis, reactions, and uses have been assembled. Collectively, these reports demonstrate the growth in this area and the promise of exploiting N-alkynyl azoles in synthesis. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Examples of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Figure 2
<p>Polarization of the <span class="html-italic">N</span>-alkynyl azole triple bond.</p> Full article ">Scheme 1
<p>Kundu and Okamoto’s synthesis of <span class="html-italic">N</span>-ethynylcarbazole.</p> Full article ">Scheme 2
<p>Pielichowski and Chrzaszcz’s phase-transfer synthesis of <span class="html-italic">N</span>-ethynylcarbazole.</p> Full article ">Scheme 3
<p>Burger and Dreier’s synthesis of an <span class="html-italic">N</span>-alkynyl pyrrole.</p> Full article ">Scheme 4
<p>Paley and coworkers’ targeted synthesis of <span class="html-italic">N</span>-ethynylpyrrole.</p> Full article ">Scheme 5
<p>Zemlicka’s synthesis of <span class="html-italic">N</span><sup>9</sup>-alkynyl purines.</p> Full article ">Scheme 6
<p>Katritzky’s ‘Corey-Fuchs’ approach to various N<sup>1</sup>-alkynyl benzotriazoles.</p> Full article ">Scheme 7
<p>Anderson’s synthesis of <span class="html-italic">N</span>-alkynyl amides and <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 8
<p>Zhao’s transition-metal free one-step synthesis of <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 9
<p>Katritzky’s Shapiro-type synthesis on an <span class="html-italic">N</span>-alkynyl pyrrole.</p> Full article ">Scheme 10
<p>Katritzky’s <span class="html-italic">N</span><sup>1</sup>-alkynyl benzotriazole synthesis.</p> Full article ">Scheme 11
<p>Mechanism of alkynyliodonium salts as alkyne-transfer reagents.</p> Full article ">Scheme 12
<p>Kitamura’s synthesis of N<sup>1</sup>-alkynyl benzotriazoles.</p> Full article ">Scheme 13
<p>Kitamura’s synthesis of N<sup>2</sup>-alkynyl benzotriazoles.</p> Full article ">Scheme 14
<p>Kerwin’s synthesis of <span class="html-italic">N</span>-alkynylimidazoles using alkynyliodonium reagents.</p> Full article ">Scheme 15
<p>Bisai’s synthesis of an <span class="html-italic">N</span>-alkynylindole.</p> Full article ">Scheme 16
<p>Toriumi and Uchiyama’s synthesis of <span class="html-italic">N</span>-alkynyl azolium salts.</p> Full article ">Scheme 17
<p>Hsung’s copper-catalyzed synthesis of various <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 18
<p>Competing alkynylation in tryptamine derivatives.</p> Full article ">Scheme 19
<p>Kerwin’s copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl imidazoles.</p> Full article ">Scheme 20
<p>Kerwin’s copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl pyrroles.</p> Full article ">Scheme 21
<p>Peters and Fu’s photoinduced-copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl carbazole.</p> Full article ">Scheme 22
<p>Burley’s microwave-promoted copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 23
<p>Das’s ligand-free copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 24
<p>Wu’s copper-catalyzed <span class="html-italic">N</span>-alkynylation of Boc-protected indoles.</p> Full article ">Scheme 25
<p>Pale’s copper-zeolite-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 26
<p>Zhang’s iron-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 27
<p>Das’s [Cu(Phen)PPh<sub>3</sub>Br]–catalyzed synthesis of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 28
<p>Stahl’s oxidative copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl indoles.</p> Full article ">Scheme 29
<p>Bhattacharjee’s oxidative copper-catalyzed synthesis of <span class="html-italic">N</span>-alkynyl pyrazoles.</p> Full article ">Scheme 30
<p>Jiao’s copper-catalyzed decarboxylative synthesis of <span class="html-italic">N</span>-alkynyl indoles.</p> Full article ">Scheme 31
<p>Brown’s flash vacuum pyrolysis synthesis of <span class="html-italic">N</span>-alkynyl pyrazole.</p> Full article ">Scheme 32
<p>Synthesis of diacetylenes of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 33
<p>Zemlicka’s synthesis of carbinols of <span class="html-italic">N</span><sup>9</sup>-alkynyl adenine.</p> Full article ">Scheme 34
<p>Wolf’s enantioselective addition of <span class="html-italic">N</span>-alkynyl indole to various aldehydes.</p> Full article ">Scheme 35
<p>Huang’s low-yielding Sonogashira coupling of an <span class="html-italic">N</span>-alkynyl purine.</p> Full article ">Scheme 36
<p>Addition of acids and thiophenol to various <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 37
<p>Neuenschwander’s rearrangement of 5-substituted 5-aminopentadienals.</p> Full article ">Scheme 38
<p>Regio- and stereoselective iodobromination of <span class="html-italic">N</span>-alkynylindoles.</p> Full article ">Scheme 39
<p>Zhu’s sulfenylchloride-mediated addition of DMSO to <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 40
<p>Zhu’s iodoamination of <span class="html-italic">N</span>-alkynyl amides and indole.</p> Full article ">Scheme 41
<p>Iodocyclizations of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 42
<p>Zhu’s iodine-mediated oxidation of <span class="html-italic">N</span>-alkynyl amides and indoles.</p> Full article ">Scheme 43
<p>Hwang’s photochemical oxidation of <span class="html-italic">N</span>-alkynyl carbazoles.</p> Full article ">Scheme 44
<p>Additions to <span class="html-italic">N</span>-alkynyl azoles under basic conditions.</p> Full article ">Scheme 45
<p>Kerwin’s regiocontrolled cyclization to imidazoazines and imidazoazoles.</p> Full article ">Scheme 46
<p>Kerwin’s synthesis of several imidazo-fused heterocycles.</p> Full article ">Scheme 47
<p>Kerwin’s synthesis of pyrrole[2,1-c]oxazin-1-ones.</p> Full article ">Scheme 48
<p>Balci’s intramolecular addition of hydrazide to <span class="html-italic">N</span>-alkynyl pyrrole.</p> Full article ">Scheme 49
<p>Gillaizeau’s cyclization of <span class="html-italic">ortho</span>-ynamidyl benzoate esters to 3-aminoisocoumarins.</p> Full article ">Scheme 50
<p>Clavier and Buono’s regioselective addition of cyclic 1,3-diones to <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 51
<p>Katritzky’s synthesis of disubstituted alkynes from <span class="html-italic">N</span>-alkynyl benzotriazole.</p> Full article ">Scheme 52
<p>Reddy’s hydroalkynylation of <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 53
<p>Park’s regiodivergent cyclization of <span class="html-italic">N</span>-alkynylindoles.</p> Full article ">Scheme 54
<p>Park’s hydroalkynylation/cyclization approach to pentacyclic heterocycles.</p> Full article ">Scheme 55
<p>Zhu’s (<span class="html-italic">Z</span>)-stereoselective boronic acid coupling to <span class="html-italic">N</span>-alkynyl amides and azoles.</p> Full article ">Scheme 56
<p>Shin’s Bronsted acid catalyzed oxygenative Friedel-Crafts coupling of an <span class="html-italic">N</span>-alkynlindole.</p> Full article ">Scheme 57
<p>Addition of hydrogen and deuteride to <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 58
<p>Zhu’s copper-catalyzed reduction of <span class="html-italic">N</span>-alkynyl amides.</p> Full article ">Scheme 59
<p>Zhu’s stereoselective hydroboration of <span class="html-italic">N</span>-alkynyl amides and indoles.</p> Full article ">Scheme 60
<p>Pirrung’s [2 + 1] cycloaddition with <span class="html-italic">N</span>-ethynyl pyrrole.</p> Full article ">Scheme 61
<p>Clavier and Buono’s [2 + 1] cycloadditions of <span class="html-italic">N</span>-alkynyl amides/azoles.</p> Full article ">Scheme 62
<p>Alcaide’s Ficini cycloaddition of <span class="html-italic">N</span>-alkynylindoles, -carbazoles, and indazoles.</p> Full article ">Scheme 63
<p>Watson and Burley’s click reaction with <span class="html-italic">N</span>-alkynyl benzimidazole.</p> Full article ">Scheme 64
<p>Watson and Burley’s orthogonal click-cycloaddition scheme.</p> Full article ">Scheme 65
<p>Metal-catalyzed formal [3 + 2] additions of <span class="html-italic">N</span>-alkynylindoles.</p> Full article ">Scheme 66
<p>Li’s cobalt-catalyzed synthesis of 5-azole-oxazoles.</p> Full article ">Scheme 67
<p>Zhou’s selenium π-acid catalyzed synthesis of 2-methylozazoles.</p> Full article ">Scheme 68
<p>Gandon and Blanchard’s [4 + 2] cycloaddition of <span class="html-italic">N</span>-substituted alkynes.</p> Full article ">Scheme 69
<p>Goswami’s [2 + 2 + 2] route to <span class="html-italic">N</span>-arylindoles and tri-indolylbenzenes.</p> Full article ">Scheme 70
<p>Saito’s [3 + 2 + 2] cycloaddition with <span class="html-italic">N</span>-alkynyl pyrrole.</p> Full article ">Scheme 71
<p>Saito’s nickel-catalyzed [4 + 3 + 2] cycloaddition with <span class="html-italic">N</span>-alkynyl pyrrole.</p> Full article ">Scheme 72
<p>Other annulations of <span class="html-italic">N</span>-alkynylindoles.</p> Full article ">Scheme 73
<p>Kerwin’s aza-Bergman cyclization-based rearrangements of dialkynylimidazoles.</p> Full article ">Scheme 74
<p>Kerwin’s dialkynylimidazole route to cyclopentapyrazines.</p> Full article ">Scheme 75
<p>Rabasso’s [<a href="#B2-molecules-24-00422" class="html-bibr">2</a>,<a href="#B3-molecules-24-00422" class="html-bibr">3</a>]-sigmatropic rearrangement of <span class="html-italic">N</span>-alkynyl indole.</p> Full article ">Scheme 76
<p>Zhao and Gagosz’s gold-catalyzed hydride shift of <span class="html-italic">N</span>-alkynyl azoles.</p> Full article ">Scheme 77
<p>Functionalization of <span class="html-italic">N</span>-alkynyl indoles.</p> Full article ">Scheme 78
<p>Beaudry’s synthesis of the bis-indole alkaloids from <span class="html-italic">Arundo donax.</span></p> Full article ">Scheme 79
<p>Pale and Beneteau’s zeolite strategy towards acortatarin A.</p> Full article ">Scheme 80
<p>Application of <span class="html-italic">N</span>-alkynyl azoles in polymerization reactions.</p> Full article ">
22 pages, 4754 KiB  
Review
Nanographene and Graphene Nanoribbon Synthesis via Alkyne Benzannulations
by Amber D. Senese and Wesley A. Chalifoux
Molecules 2019, 24(1), 118; https://doi.org/10.3390/molecules24010118 - 30 Dec 2018
Cited by 59 | Viewed by 9365
Abstract
The extension of π-conjugation of polycyclic aromatic hydrocarbons (PAHs) via alkyne benzannulation reactions has become an increasingly utilized tool over the past few years. This short review will highlight recent work of alkyne benzannulations in the context of large nanographene as well as [...] Read more.
The extension of π-conjugation of polycyclic aromatic hydrocarbons (PAHs) via alkyne benzannulation reactions has become an increasingly utilized tool over the past few years. This short review will highlight recent work of alkyne benzannulations in the context of large nanographene as well as graphene nanoribbon synthesis along with a brief discussion of the interesting physical properties these molecules display. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Figure 1

Figure 1
<p>X-ray crystal structures of peropyrene <b>49</b> and teropyrene <b>50</b>.</p> Full article ">Figure 2
<p>(<b>a</b>) Sterically hindered chiral peropyrene <b>107</b> [<a href="#B116-molecules-24-00118" class="html-bibr">116</a>]. (<b>b</b>) BDPs <b>108</b> and <b>109</b> synthesized by a four-fold alkyne benzannulation [<a href="#B117-molecules-24-00118" class="html-bibr">117</a>].</p> Full article ">Scheme 1
<p>(<b>a</b>) Benzene <b>2</b> from the pyrolysis of 1,3-hexadien-5-yne <b>1</b> [<a href="#B17-molecules-24-00118" class="html-bibr">17</a>]. (<b>b</b>) FVP of <b>3</b> to produce corannulene <b>4</b> [<a href="#B20-molecules-24-00118" class="html-bibr">20</a>]. Two-fold [<a href="#B21-molecules-24-00118" class="html-bibr">21</a>] and four-fold alkyne benzannulations [<a href="#B22-molecules-24-00118" class="html-bibr">22</a>] to afford bowl-shaped NGs (<b>c</b>) <b>6</b> and (<b>d</b>) <b>8</b>, respectively.</p> Full article ">Scheme 2
<p>Alkyne benzannulation of (<b>a</b>) 2-ethynylbiphenyl derivatives <b>9</b> [<a href="#B23-molecules-24-00118" class="html-bibr">23</a>] and (<b>b</b>) 1,4-diaryl-1-buten-3-ynes <b>11</b> [<a href="#B24-molecules-24-00118" class="html-bibr">24</a>,<a href="#B25-molecules-24-00118" class="html-bibr">25</a>] via a photocyclization reaction to afford phenanthrene products <b>10</b> and <b>12</b>.</p> Full article ">Scheme 3
<p>Electrophilic benzannulation with either an iodonium salt or a Brønsted acid [<a href="#B28-molecules-24-00118" class="html-bibr">28</a>].</p> Full article ">Scheme 4
<p>ICl-induced benzannulation used in the synthesis towards dibenzo[g,p]chrysene derivatives [<a href="#B29-molecules-24-00118" class="html-bibr">29</a>].</p> Full article ">Scheme 5
<p>Müllen and coworkers synthesis of zigzag NGs [<a href="#B31-molecules-24-00118" class="html-bibr">31</a>].</p> Full article ">Scheme 6
<p>Synthetic route to [5]helicene-like compounds [<a href="#B35-molecules-24-00118" class="html-bibr">35</a>].</p> Full article ">Scheme 7
<p>Radical mediated cascade alkyne benzannulations to arrive at (<b>a</b>) NG <b>32</b> [<a href="#B40-molecules-24-00118" class="html-bibr">40</a>], (<b>b</b>) helical NGs <b>34</b>/<b>35</b> [<a href="#B42-molecules-24-00118" class="html-bibr">42</a>], and (<b>c</b>) olympicene <b>37</b> [<a href="#B44-molecules-24-00118" class="html-bibr">44</a>].</p> Full article ">Scheme 8
<p>Brønsted acid-induced alkyne benzannulations of (<b>a</b>) <span class="html-italic">para</span>- (<b>38</b>), (<b>b</b>) <span class="html-italic">meta</span>- (<b>40</b>) and (<b>c</b>) <span class="html-italic">ortho</span>-substituted (<b>42</b>) terphenyl systems to afford NGs [<a href="#B46-molecules-24-00118" class="html-bibr">46</a>].</p> Full article ">Scheme 9
<p>Brønsted acid-promoted two-fold and four-fold alkyne benzannulations to afford pyrenes <b>48</b>, peropyrenes <b>49</b>, and teropyrenes <b>50</b> [<a href="#B48-molecules-24-00118" class="html-bibr">48</a>,<a href="#B49-molecules-24-00118" class="html-bibr">49</a>].</p> Full article ">Scheme 10
<p>Four-fold alkyne benzannulation towards chiral peropyrenes <b>53</b> [<a href="#B50-molecules-24-00118" class="html-bibr">50</a>].</p> Full article ">Scheme 11
<p>(<b>a</b>) Synthesis of GNRs <b>55</b> by Swager and coworker [<a href="#B28-molecules-24-00118" class="html-bibr">28</a>]. (<b>b</b>) Synthesis of expanded GNRs <b>57</b> by Wu, Zhao and coworkers [<a href="#B66-molecules-24-00118" class="html-bibr">66</a>].</p> Full article ">Scheme 12
<p>Soluble GNR <b>59</b> reported by Chalifoux and coworkers [<a href="#B67-molecules-24-00118" class="html-bibr">67</a>].</p> Full article ">Scheme 13
<p>First synthesis of coronene <b>61</b> using a Ru(II)-catalyzed four-fold alkyne benzannulation [<a href="#B77-molecules-24-00118" class="html-bibr">77</a>].</p> Full article ">Scheme 14
<p>Synthesis of GNRs <b>65</b>–<b>67</b> via a Ru(II)-catalyzed two-fold alkyne benzannulation by Liu and coworkers [<a href="#B79-molecules-24-00118" class="html-bibr">79</a>]. [Tp = tris(1-pyrazolyl)borate)]</p> Full article ">Scheme 15
<p>Pt-catalyzed alkyne benzannulation to afford chrysene <b>69</b> [<a href="#B83-molecules-24-00118" class="html-bibr">83</a>,<a href="#B87-molecules-24-00118" class="html-bibr">87</a>].</p> Full article ">Scheme 16
<p>Cove-edge NGs produced from Pt(II)-catalyzed alkyne benzannulations [<a href="#B85-molecules-24-00118" class="html-bibr">85</a>].</p> Full article ">Scheme 17
<p>1Pt(II)-catalyzed benzannulation towards functionalized coronenes <b>79</b> [<a href="#B96-molecules-24-00118" class="html-bibr">96</a>].</p> Full article ">Scheme 18
<p>(<b>a</b>) [6]Helicene <b>83</b> and aza[6]helicene <b>84</b> synthesis by Storch and coworkers [<a href="#B99-molecules-24-00118" class="html-bibr">99</a>]. (<b>b</b>) Aza[6]helicenes <b>86</b> and <b>87</b> synthesized by Fuchter and coworkers [<a href="#B101-molecules-24-00118" class="html-bibr">101</a>].</p> Full article ">Scheme 19
<p>Asao-Yamamoto alkyne benzannulation reported by Dichtel and coworkers towards NGs <b>91</b> and <b>92</b> [<a href="#B111-molecules-24-00118" class="html-bibr">111</a>].</p> Full article ">Scheme 20
<p>Synthesis of compounds <b>94</b> by a two-fold alkyne benzannulation using InCl<sub>3</sub> [<a href="#B70-molecules-24-00118" class="html-bibr">70</a>].</p> Full article ">Scheme 21
<p>InCl<sub>3</sub>-catalyzed alkyne benzannulation towards a broad scope of (<b>a</b>) peropyrenes <b>96</b>–<b>100</b> and (<b>b</b>) teropyrenes <b>102</b>–<b>106</b> [<a href="#B116-molecules-24-00118" class="html-bibr">116</a>].</p> Full article ">Scheme 22
<p>(<b>a</b>) Regioselective domino alkyne benzannulation of diynes to form various NGs <b>112</b>–<b>117</b>. (<b>b</b>) Four-fold alkyne benzannulation towards a chiral butterfly ligand motif <b>119</b> [<a href="#B118-molecules-24-00118" class="html-bibr">118</a>].</p> Full article ">Scheme 23
<p>Base-mediated alkyne benzannulations towards CDIs <b>121</b> [<a href="#B123-molecules-24-00118" class="html-bibr">123</a>].</p> Full article ">
16 pages, 5505 KiB  
Review
Recent Synthesis Developments of Organoboron Compounds via Metal-Free Catalytic Borylation of Alkynes and Alkenes
by Yanmei Wen, Chunmei Deng, Jianying Xie and Xinhuang Kang
Molecules 2019, 24(1), 101; https://doi.org/10.3390/molecules24010101 - 28 Dec 2018
Cited by 48 | Viewed by 9538
Abstract
Diboron reagents have been traditionally regarded as “Lewis acids”, which can react with simple Lewis base to create a significant nucleophilic character in one of boryl moieties. In particular, bis(pinacolato)diboron (B2pin2) reacts with simple Lewis bases, such as N [...] Read more.
Diboron reagents have been traditionally regarded as “Lewis acids”, which can react with simple Lewis base to create a significant nucleophilic character in one of boryl moieties. In particular, bis(pinacolato)diboron (B2pin2) reacts with simple Lewis bases, such as N-heterocyclic carbenes (NHCs), phosphines and alkoxides. This review focuses on the application of trivalent nucleophilic boryl synthon in the selective preparation of organoboron compounds, mainly through metal-free catalytic diboration and the β-boration reactions of alkynes and alkenes. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Scheme 1

Scheme 1
<p>(<b>a</b>) Transition-metal-free diboration reaction of non-activated olefins; (<b>b</b>) Mixed organocatalytic diboration of non-activated olefins.</p> Full article ">Scheme 2
<p>Suggested catalytic cycle for the diboration of non-activated olefins.</p> Full article ">Scheme 3
<p>(<b>a</b>) Phosphine-Catalyzed 1,2-diboration of alkynoate; (<b>b</b>) 1,2-diboration of N-substituted phenylpropiolamides.</p> Full article ">Scheme 4
<p>Trans-selective diborylation reaction of propargylic alcohols.</p> Full article ">Scheme 5
<p>Reaction of pinB–BMes<sub>2</sub> with terminal alkynes.</p> Full article ">Scheme 6
<p>(<b>a</b>) Synthesis of 1,1-diborylalkenes, (<b>b</b>) Synthesis of functionalized geminal-diborylalkanes.</p> Full article ">Scheme 7
<p>Enantioselective diboration of olefins. (<b>a</b>) synthesis of the 1,2-diborated product; (<b>b</b>) synthesis of pseudoenantiomeric glycol 6-tertbutyldimethylsilyl-1,2-dihydroglucal (<b>4</b>) and dihydrorhamnal (<b>5</b>); (<b>c</b>) synthesis of diboration of cyclic and acyclic homoallylic and bishomoallylic alcohol substrates.</p> Full article ">Scheme 8
<p>The β-borylation of α,β-unsaturated carbonyl compounds.</p> Full article ">Scheme 9
<p>Mechanism for B<sub>2</sub>pin<sub>2</sub> activation and conjugate addition to an enone.</p> Full article ">Scheme 10
<p>Formation of the sp<sup>2</sup>–sp<sup>3</sup> hybridized NHC·B<sub>2</sub>(pin)<sub>2</sub> compound.</p> Full article ">Scheme 11
<p>(<b>a</b>) NHC-catalyzed enantioselective boryl conjugate addition to unsaturated carbonyls, (<b>b</b>) NHC-catalyzed enantioselective boryl conjugate addition to enones.</p> Full article ">Scheme 12
<p>Verkade’s base mediates β-boration of ethyl crotonate.</p> Full article ">Scheme 13
<p>Proposed reaction pathway for β-boration of methyl acrylate.</p> Full article ">Scheme 14
<p>(<b>a</b>) The β-boration of α,β-unsaturated compounds, (<b>b</b>) The β-boration of in situ formed α,β-unsaturated imines.</p> Full article ">Scheme 15
<p>Phosphine-mediated asymmetric β-boration of α,β-unsaturated compounds.</p> Full article ">Scheme 16
<p>Plausible mechanism for the phosphine-catalyzed β-boration of α,β-unsaturated carbonyl compound.</p> Full article ">Scheme 17
<p>Phosphine assisted β-boration reaction of α,β-unsaturated carbonyl compounds in MeOH.</p> Full article ">Scheme 18
<p>Ion pair formation.</p> Full article ">Scheme 19
<p>One-pot three-component synthesis of homoallylboranes.</p> Full article ">Scheme 20
<p>(<b>a</b>) Borylation of tertiary allylic alcohols, (<b>b</b>) Borylation of propargylic alcohols.</p> Full article ">Scheme 21
<p>Suggested mechanism for the metal-free allylic borylation.</p> Full article ">Scheme 22
<p>Direct conversion of allylic alcohols to allylic boronates.</p> Full article ">Scheme 23
<p>Trans-selective alkynylboration reaction of alkynes.</p> Full article ">Scheme 24
<p>(<b>a</b>) Synthesis of alkylboronates from arylacetylenes and vinyl arenes, (<b>b</b>) Synthesis of β-vinylboronates from terminal alkynes, (<b>c</b>) Synthesis of 1,2-diborylalkanes from non-activated olefins, (<b>d</b>) Synthesis of 1,2,3-triborated compounds from 1,3-dienes.</p> Full article ">Scheme 25
<p>Transition-metal-free hydroboration of allenamides.</p> Full article ">
84 pages, 68329 KiB  
Review
Acetylene in Organic Synthesis: Recent Progress and New Uses
by Vladimir V. Voronin, Maria S. Ledovskaya, Alexander S. Bogachenkov, Konstantin S. Rodygin and Valentine P. Ananikov
Molecules 2018, 23(10), 2442; https://doi.org/10.3390/molecules23102442 - 24 Sep 2018
Cited by 134 | Viewed by 17284
Abstract
Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and [...] Read more.
Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and the construction of a number of functionalized molecules with different levels of molecular complexity were recently studied. Of particular importance is the utilization of acetylene in the synthesis of pharmaceutical substances and drugs. The increasing interest in acetylene and its involvement in organic transformations highlights a fascinating renaissance of this simplest alkyne molecule. Full article
(This article belongs to the Special Issue Alkynes: From Reaction Design to Applications in Organic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Effect of reaction temperature on acetylene hydrocarboxylation. Reaction conditions: [Pd<sub>2</sub>(dba)<sub>3</sub>]·CHCl<sub>3</sub> (2.5 mmol), Xantphos (50 mmol), benzoic anhydride (0.1 mmol), HCO<sub>2</sub>H (1.5 mmol), acetylene (initial pressure 10 atm, ca.12 mmol), in THF (3 mL) for 12 h (reproduced with permission from [<a href="#B28-molecules-23-02442" class="html-bibr">28</a>]. Copyright 2015, WILEY-VCH Verlag GmbH &amp; Co., KGaA).</p> Full article ">Figure 2
<p>Effect of initial pressure on acetylene hydrocarboxylation. Reaction conditions: [Pd<sub>2</sub>(dba)<sub>3</sub>]·CHCl<sub>3</sub> (2.5 mmol), Xantphos (50 mmol), benzoic anhydride (0.1 mmol), HCO<sub>2</sub>H (1.5 mmol), in THF (3 mL) at 100 °C for 12 h (reproduced with permission from [<a href="#B28-molecules-23-02442" class="html-bibr">28</a>]. Copyright 2015, WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 3
<p>Effect of FA formic acid concentration on acetylene hydrocarboxylation. Reaction conditions: [Pd<sub>2</sub>(dba)<sub>3</sub>]·CHCl<sub>3</sub> (2.5 mmol), Xantphos (50 mmol), benzoic anhydride (0.1 mmol), acetylene (initial pressure 15 atm, ca. 18 mmol), in THF (3 mL) at 100 °C for 12 h (reproduced with permission from [<a href="#B28-molecules-23-02442" class="html-bibr">28</a>]. Copyright 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 4
<p>Effect of reaction time on acetylene hydrocarboxylation. Reaction conditions: [Pd<sub>2</sub>(dba)<sub>3</sub>]·CHCl<sub>3</sub> (2.5 mmol), Xantphos (50 mmol), benzoic anhydride (0.1 mmol), HCO<sub>2</sub>H (3 mmol), acetylene (initial pressure 15 atm, ca.18 mmol), in THF (3 mL) at 100 °C (reproduced with permission from [<a href="#B28-molecules-23-02442" class="html-bibr">28</a>]. Copyright 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 5
<p>HR TEM images of palladium NPs after 2 h (<b>a</b>) and 55 h (<b>b</b>) of the reaction. White arrows indicate the sunken regions with steps and terraces. (Reproduced with permission from ref. [<a href="#B248-molecules-23-02442" class="html-bibr">248</a>]. Copyright 2017 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.).</p> Full article ">Figure 6
<p>Ethylene selectivity as a function of acetylene conversion. Pd(I)-catalysts without defined morphology prepared by using the incipient wetness impregnation; Pd(S)-catalyst with spherical particles; Pd(C)-catalyst with cubic particles. Negative ethylene selectivity indicates net loss of ethylene due to over-hydrogenation and ethane production (reproduced with permission from [<a href="#B249-molecules-23-02442" class="html-bibr">249</a>]. Copyright 2013, Elsevier Inc.).</p> Full article ">Figure 7
<p>Plots of acetylene conversion and ethylene selectivity for Pd on different supports. (reproduced with permission from [<a href="#B250-molecules-23-02442" class="html-bibr">250</a>], Copyright 2015, Elsevier Inc.).</p> Full article ">Figure 8
<p>(<b>a</b>) SEM image of Pd/α-Al<sub>2</sub>O<sub>3</sub>@SiC catalyst, (<b>b</b>) TEM image of Pd particles on Al<sub>2</sub>O<sub>3</sub> layer of Pd/α-Al<sub>2</sub>O<sub>3</sub>@SiC catalyst (reproduced with permission from [<a href="#B252-molecules-23-02442" class="html-bibr">252</a>]. Copyright 2016, the Royal Society of Chemistry).</p> Full article ">Figure 9
<p>Porous hollow silica NPs (<b>A</b>) and monolithic cordierite (<b>B</b>) (reproduced with permission from [<a href="#B253-molecules-23-02442" class="html-bibr">253</a>]. Copyright 2013, Elsevier Inc.).</p> Full article ">Figure 10
<p>Hydrogenation rates of acetylene (black) and ethylene (shaded green): 1—Pd/TiO<sub>2</sub>, 2—Pd/TiO<sub>2</sub> with 3‰ CO in feed, 3—PPh<sub>3</sub> 2.5 Pd/TiO<sub>2</sub> (reproduced with permission from [<a href="#B263-molecules-23-02442" class="html-bibr">263</a>]. Copyright 2015, the Royal Society of Chemistry).</p> Full article ">Figure 11
<p>Performance of various Ti-modified Pd–La catalysts in acetylene hydrogenation. (H<sub>2</sub>/Acetylene = 2, reaction temperature = 60 °C). (a) Pd/300, (b) Pd–1La/300, (c) Pd–1La/500, (d) Pd–1La–0.1Ti/300, (e) Pd–1La–0.2Ti/300, (f) Pd–1La–0.4Ti/300, (g) Pd–0.2Ti/300 (reproduced with permission from [<a href="#B264-molecules-23-02442" class="html-bibr">264</a>]. Copyright 2014, Elsevier Inc.).</p> Full article ">Figure 12
<p>Solubility of acetylene and ethylene in NMP and decane. The catalyst is Pd/low surface area silica gel (reproduced with permission from [<a href="#B265-molecules-23-02442" class="html-bibr">265</a>]. Copyright 2013, American Chemical Society.).</p> Full article ">Figure 13
<p>SEM images of the of the bimetallic Pd/Ga catalyst precursor from the surface (<b>a</b>) and in the cross section (<b>b</b>) (reproduced with permission from [<a href="#B269-molecules-23-02442" class="html-bibr">269</a>]. Copyright 2014, Elsevier Inc.).</p> Full article ">Figure 14
<p>Schematic drawing of supported Pd particles in Pd/Al<sub>2</sub>O<sub>3</sub>- and Ga<sub>2</sub>O<sub>3</sub>-coated Pd particles in 1c-Ga<sub>2</sub>O<sub>3</sub>−Pd/Al<sub>2</sub>O<sub>3</sub> and 3c-Ga<sub>2</sub>O<sub>3</sub>−Pd/Al<sub>2</sub>O<sub>3</sub>. The red, blue, green, orange, and yellow spheres represent terrace atoms of Pd (111) facets, facets other than Pd(111), corner and edge atoms of Pd(111) facets, Al<sub>2</sub>O<sub>3</sub>, and Ga<sub>2</sub>O<sub>3</sub>, respectively (reproduced with permission from [<a href="#B273-molecules-23-02442" class="html-bibr">273</a>]. Copyright 2016, American Chemical Society).</p> Full article ">Figure 15
<p>TEM images and particle size distributions of the catalysts: <b>a</b>—1%-Pd/ZnO; <b>b</b>—0.1%-Pd/ZnO; <b>c</b>—0.01%-Pd/ZnO reduced at 100 °C (reproduced with permission from [<a href="#B274-molecules-23-02442" class="html-bibr">274</a>]. Copyright 2016, Elsevier Inc.).</p> Full article ">Figure 16
<p>TEM pattern (<b>a</b>), HAADF-STEM image (<b>b</b>), and EDX mapping (<b>c</b>) of Pd@H-Zn/Co-ZIF. TEM pattern (<b>d</b>), HAADF-STEM image (<b>e</b>), and EDX mapping (<b>f</b>) of Pd@S-Zn/Co-ZIF. Acetylene conversion (<b>g</b>) and ethylene selectivity (<b>h</b>) as functions of temperature (reproduced with permission from [<a href="#B276-molecules-23-02442" class="html-bibr">276</a>]. Copyright 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 17
<p>Representative TEM images of the Co, Pd and CoPd nanoparticles and structures formed after refluxing for 1 h at 195 °C in EG or at 280 °C in TEG. EG—ethylene glycol, TEG —tri-ethylene glycol (reproduced with permission from [<a href="#B277-molecules-23-02442" class="html-bibr">277</a>]. Copyright 2013, Elsevier Inc.).</p> Full article ">Figure 18
<p>Acetylene conversion (<b>a</b>), ethylene selectivity (<b>b</b>), and C4 selectivity (<b>c</b>) as functions of temperature. Acetylene conversion is given by the difference of the inlet and outlet concentrations in vol %. Ethane formation is given by vol% of ethane in the reactor off-gas. (Conditions: 0.5 vol % C<sub>2</sub>H<sub>2</sub>, 1 vol % H<sub>2</sub>, and 70 vol % C<sub>2</sub>H<sub>4</sub> in N<sub>2</sub>, flow velocity 50 mL/min.) (reproduced with permission from [<a href="#B277-molecules-23-02442" class="html-bibr">277</a>]. Copyright 2013, Elsevier Inc.).</p> Full article ">Figure 18 Cont.
<p>Acetylene conversion (<b>a</b>), ethylene selectivity (<b>b</b>), and C4 selectivity (<b>c</b>) as functions of temperature. Acetylene conversion is given by the difference of the inlet and outlet concentrations in vol %. Ethane formation is given by vol% of ethane in the reactor off-gas. (Conditions: 0.5 vol % C<sub>2</sub>H<sub>2</sub>, 1 vol % H<sub>2</sub>, and 70 vol % C<sub>2</sub>H<sub>4</sub> in N<sub>2</sub>, flow velocity 50 mL/min.) (reproduced with permission from [<a href="#B277-molecules-23-02442" class="html-bibr">277</a>]. Copyright 2013, Elsevier Inc.).</p> Full article ">Figure 19
<p>Conversion (A) and (B) selectivity as functions of temperature for acetylene semi-hydrogenation over Au/SiO<sub>2</sub>, AuPd<sub>0.01</sub>/SiO<sub>2</sub>, AuPd<sub>0.025</sub>/SiO<sub>2</sub> and AuPd<sub>0.1</sub>/SiO<sub>2</sub> catalysts (reproduced with permission from [<a href="#B278-molecules-23-02442" class="html-bibr">278</a>]. Copyright 2014, the Royal Society of Chemistry.).</p> Full article ">Figure 20
<p>Product selectivities (<b>a</b>) and C<sub>2</sub>H<sub>4</sub> yields (<b>b</b>) for PdAg/ZnAl catalysts, 180 min at 90 °C (reproduced with permission from [<a href="#B283-molecules-23-02442" class="html-bibr">283</a>]. Copyright 2017 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 20 Cont.
<p>Product selectivities (<b>a</b>) and C<sub>2</sub>H<sub>4</sub> yields (<b>b</b>) for PdAg/ZnAl catalysts, 180 min at 90 °C (reproduced with permission from [<a href="#B283-molecules-23-02442" class="html-bibr">283</a>]. Copyright 2017 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 21
<p>Proposed mechanism of acetylene hydrogenation over a Pd/Cu catalyst with deposited carbonaceous layer (reproduced with permission from r [<a href="#B287-molecules-23-02442" class="html-bibr">287</a>]. Copyright 2017, American Chemical Society.).</p> Full article ">Figure 22
<p>Proposed mechanism of acetylene hydrogenation over a silica-supported Pd/Cu single atom catalyst: <b>a</b>—dissociation of H<sub>2</sub> and spillover of H atoms, <b>b</b>—adsorption and hydrogenation of acetylene, <b>c</b>—desorption of ethylene (reproduced with permission from [<a href="#B288-molecules-23-02442" class="html-bibr">288</a>]. Copyright 2017 American Chemical Society.).</p> Full article ">Figure 23
<p>(<b>a</b>) Experimental kinetic curves of C<sub>2</sub>H<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> accumulation in the reaction of C<sub>2</sub>H<sub>2</sub> reduction by Na or Eu amalgam in the presence of Mo-complex. (<b>b</b>) The effect of PBu<sub>3</sub> addition (C(PBu<sub>3</sub>) = 5 × 10<sup>−3</sup> M) on the C<sub>2</sub>H<sub>4</sub> accumulation rate in C<sub>2</sub>H<sub>2</sub> reduction by Na amalgam in the presence of Mo-complex. (Conditions: C(Mo) = 2 × 10<sup>−5</sup> M; 0.5 mL Eu/Hg (0.9 M) or 0.5 mL Na/Hg (3.5 M); 8 ml CH<sub>3</sub>OH; P(C<sub>2</sub>H<sub>2</sub>) = 0.13 atm, C(NaOCH<sub>3</sub>) = 0.09 M, C(H<sub>2</sub>O) = 0.02 M, C(PC) = 3 × 10<sup>−4</sup> M, 21 °C) (reproduced with permission from [<a href="#B291-molecules-23-02442" class="html-bibr">291</a>]. Copyright 2016 the Royal Society of Chemistry.).</p> Full article ">Figure 24
<p>Transition states for vinyl hydrogenation and C–C bond formation on Ni(111) (<b>A</b> and <b>B</b>) and NiZn(101) (<b>C</b> and <b>D</b>), respectively. Ni atoms are light pink and Zn atoms are dark blue (reproduced with permission from [<a href="#B294-molecules-23-02442" class="html-bibr">294</a>]. Copyright 2014 Elsevier Inc.).</p> Full article ">Figure 25
<p>Proposed mechanism of reductive elimination (RE) of H<sub>2</sub> from the dihydride Fe/Mo species <b>2</b> and C<sub>2</sub>H<sub>4</sub> from the vinyl monohydride Fe/Mo species <b>3</b>. The scale of horizontal axis represents oxidation states 0 to –4, with the initial oxidation state of <b>1</b> corresponding to 0. Accordingly, the two and four electron-deprived species correspond to –2 and –4 oxidation states, respectively (reproduced with permission from [<a href="#B302-molecules-23-02442" class="html-bibr">302</a>]. Copyright 2016 the Royal Society of Chemistry.).</p> Full article ">Figure 26
<p>Acetylene conversion X (black symbols, left axis) and ethane time yield Y (gray symbols, right axis) as functions of temperature for: <b><span class="html-italic">Left</span></b> monometallic Pt/SiO<sub>2</sub> (circles) and DDA-Pt/SiO<sub>2</sub> (stars) catalysts. <b><span class="html-italic">Right</span></b> Pt/SiO<sub>2</sub> (filled symbols), Pt/Sn(1:1)/SiO<sub>2</sub> as prepared (half-filled symbols), and PtSn(1:1)/SiO<sub>2</sub> prereduced (empty symbols) catalysts. Acetylene conversion is given by the difference in the reactor inlet and outlet concentrations in vol %. Ethane yield is given by vol % of ethane in the reactor off-gas. Reaction conditions: 0.5 vol % C<sub>2</sub>H<sub>2</sub>; 1 vol % H<sub>2</sub>; 70 vol % C<sub>2</sub>H<sub>4</sub>; rest N<sub>2</sub>; flow velocity 50 mLmin<sup>−1</sup> (reproduced with permission from [<a href="#B304-molecules-23-02442" class="html-bibr">304</a>]. Copyright 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 27
<p>Reaction rate and ethylene selectivity over the SBA-15 supported Cu (<b>a</b>), Cu<sub>10</sub>Au<sub>1</sub> (<b>b</b>), Cu<sub>3</sub>Au<sub>1</sub> (c), Cu<sub>1</sub>Au<sub>3</sub> (d), and Au (e) catalysts. C<sub>2</sub>H<sub>2</sub>/H<sub>2</sub>/He = 1.5/15/83.5, GHSV = 40,000 mL g<sup>−1</sup> <sub>cat</sub> h<sup>−1</sup> (reproduced with permission from [<a href="#B305-molecules-23-02442" class="html-bibr">305</a>]. Copyright 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 27 Cont.
<p>Reaction rate and ethylene selectivity over the SBA-15 supported Cu (<b>a</b>), Cu<sub>10</sub>Au<sub>1</sub> (<b>b</b>), Cu<sub>3</sub>Au<sub>1</sub> (c), Cu<sub>1</sub>Au<sub>3</sub> (d), and Au (e) catalysts. C<sub>2</sub>H<sub>2</sub>/H<sub>2</sub>/He = 1.5/15/83.5, GHSV = 40,000 mL g<sup>−1</sup> <sub>cat</sub> h<sup>−1</sup> (reproduced with permission from [<a href="#B305-molecules-23-02442" class="html-bibr">305</a>]. Copyright 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 28
<p>TEM and SEM images (on left and right, respectively) of the MWCNT and MWCNT-400 samples (top and bottom panels, respectively) (reproduced with permission from [<a href="#B307-molecules-23-02442" class="html-bibr">307</a>]. Copyright 2017 WILEY-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 29
<p>Acetylene conversion by AuCl<sub>3</sub>/C catalysts: temperature activation (<b>up</b>) and acid treatment (<b>down</b>). Reaction conditions: temperature = 180 °C, C<sub>2</sub>H<sub>2</sub> GHSV = 360 h<sup>−1</sup>, feed volume ratio between HCl and C<sub>2</sub>H<sub>2</sub> = 1.1 (reproduced with permission from [<a href="#B313-molecules-23-02442" class="html-bibr">313</a>]. Copyright 2015 Elsevier Inc.).</p> Full article ">Figure 30
<p>Acetylene conversion (<b>a</b>) and VCM selectivity (<b>b</b>) over monometallic Ru, Cu, and Co catalysts (reproduced with permission from [<a href="#B330-molecules-23-02442" class="html-bibr">330</a>]. Copyright 2013 the Royal Society of Chemistry.).</p> Full article ">Figure 31
<p>Acetylene conversion (<b>a</b>) and VCM selectivity (<b>b</b>) over 1%Ru, 1%Ru1Cu1, and 1%Ru1Co3 catalysts (reproduced with permission from [<a href="#B330-molecules-23-02442" class="html-bibr">330</a>]. Copyright 2013 the Royal Society of Chemistry.).</p> Full article ">Figure 32
<p>Calculated TOF values for Cu400Ru/MWCNTs in comparison with a variety of reported catalysts. The calculated TOF values for the different catalyst materials reported in literature and the Cu400Ru/MWCNTs catalyst material. (Reproduced with permission from ref. [<a href="#B333-molecules-23-02442" class="html-bibr">333</a>]. Copyright 2015 the Royal Society of Chemistry.).</p> Full article ">Figure 33
<p>Using both alkyne π-bonds as “two functional groups in one package”. (Reproduced with permission from ref. [<a href="#B338-molecules-23-02442" class="html-bibr">338</a>]. Copyright 2013 American Chemical Society.).</p> Full article ">Figure 34
<p>Comparison of alkene and alkyne reactivities in terms of kinetics and thermodynamics (reproduced with permission from [<a href="#B339-molecules-23-02442" class="html-bibr">339</a>]. Copyright 2018 American Chemical Society).</p> Full article ">Figure 35
<p>Examples of polyaromatic self-assembling based on the cascade oligocyclization of alkynes (reproduced with permission from [<a href="#B341-molecules-23-02442" class="html-bibr">341</a>]. Copyright 2012 American Chemical Society).</p> Full article ">Scheme 1
<p>Representative examples in acetylene chemistry.</p> Full article ">Scheme 2
<p>Synthesis of vinyl ethers involving acetylene.</p> Full article ">Scheme 3
<p>3,4,5-Trimethoxybenzyl vinyl ether synthesis.</p> Full article ">Scheme 4
<p>Triterpenoid vinylation.</p> Full article ">Scheme 5
<p>Reaction of ferrocene-derived alcohols with acetylene.</p> Full article ">Scheme 6
<p>Reaction of calcium carbide with water.</p> Full article ">Scheme 7
<p>Vinylation of benzyl alcohols with calcium carbide.</p> Full article ">Scheme 8
<p>Vinylation of alcohols with calcium carbide.</p> Full article ">Scheme 9
<p>The synthesis of aryl vinyl ethers with calcium carbide.</p> Full article ">Scheme 10
<p>Polyvinyl ethers synthesis with in situ generated acetylene.</p> Full article ">Scheme 11
<p>Representative scope of alcohols vinylation with CaC<sub>2</sub> in KOH-DMSO-KF system.</p> Full article ">Scheme 12
<p>Addition of thiols to acetylene.</p> Full article ">Scheme 13
<p>Reactions of carbide-induced acetylene with thiols.</p> Full article ">Scheme 14
<p>Phenyl vinyl selenide synthesis with calcium carbide.</p> Full article ">Scheme 15
<p>Vinyl chalcogenide synthesis.</p> Full article ">Scheme 16
<p>The mechanism of vinyl chalcogenides formation.</p> Full article ">Scheme 17
<p>Reactions of carbide-induced acetylene with dichalcogenides.</p> Full article ">Scheme 18
<p><span class="html-italic">N</span>-Vinyl indole synthesis.</p> Full article ">Scheme 19
<p>Vinylation of indoles with carbide-induced acetylene.</p> Full article ">Scheme 20
<p>Representative scope of amine core vinylation with CaC<sub>2</sub>.</p> Full article ">Scheme 21
<p>Styrenes synthesis with acetylene.</p> Full article ">Scheme 22
<p>Modification of <span class="html-italic">N</span>-benzyl-3-hydroxy-2-oxindole with acetylene.</p> Full article ">Scheme 23
<p>Catalytic carbonylation of acetylene.</p> Full article ">Scheme 24
<p>Hydrocarboxylation of acetylene with FA.</p> Full article ">Scheme 25
<p>Palladium-catalyzed hydrocarbonylation of terminal alkynes.</p> Full article ">Scheme 26
<p>Synthesis of Pd–PyPPh<sub>2</sub>–SO<sub>3</sub>H@POPs catalyst. <span class="html-italic">Reagents and conditions</span>: (i) H<sub>2</sub>O, THF, AIBN, 120 °C; (ii) 1M H<sub>2</sub>SO<sub>4</sub>; (iii) Pd(OAc)<sub>2</sub>, THF.</p> Full article ">Scheme 27
<p>Palladium-catalyzed Sonogashira coupling of acetylene with methyl 4-iodobenzoate.</p> Full article ">Scheme 28
<p>Cross-coupling with CaC<sub>2</sub>-derived acetylene.</p> Full article ">Scheme 29
<p>Catalytic synthesis of diphenylacetylene.</p> Full article ">Scheme 30
<p>Catalytic synthesis of diarylethynes.</p> Full article ">Scheme 31
<p>Sonogashira coupling with aryl iodides in a flow reactor.</p> Full article ">Scheme 32
<p>TBAF-promoted Sonogashira coupling of arylhalides with CaC<sub>2</sub>-derived acetylene.</p> Full article ">Scheme 33
<p>Three-component aldehyde-alkyne-amine coupling.</p> Full article ">Scheme 34
<p>Copper-catalyzed Sonogashira-type allylation.</p> Full article ">Scheme 35
<p>Gold-catalyzed oxidative homocoupling.</p> Full article ">Scheme 36
<p>Synthesis of secondary propargyl alcohols from aldehydes.</p> Full article ">Scheme 37
<p>Reaction of alkyl aryl ketones with acetylene.</p> Full article ">Scheme 38
<p>Bu<sub>4</sub>NOH-mediated alkynylation of carbonyl compounds.</p> Full article ">Scheme 39
<p>Synthesis of ferrocene-substituted propargyl alcohols.</p> Full article ">Scheme 40
<p>Favorskii alkynylation with in situ generated ethynylmagnesium bromide.</p> Full article ">Scheme 41
<p>Favorskii alkynylation with in situ generated lithium acetylide.</p> Full article ">Scheme 42
<p>Favorskii reaction with in situ generated acetylene.</p> Full article ">Scheme 43
<p>[3 + 2]-Cycloaddition of azides to acetylene, method 1.</p> Full article ">Scheme 44
<p>[3 + 2]-Cycloaddition of azides to acetylene, method 2.</p> Full article ">Scheme 45
<p>Click-reaction of <span class="html-italic">o</span>-iodo-azides with C<sub>2</sub>H<sub>2</sub>.</p> Full article ">Scheme 46
<p>Cycloaddition with CaC<sub>2</sub>.</p> Full article ">Scheme 47
<p>Synthesis of NH-pyrazoles from N-tosylhydrazones.</p> Full article ">Scheme 48
<p><span class="html-italic">NH</span>-Pyrazole formation mechanism.</p> Full article ">Scheme 49
<p>CaC<sub>2</sub>-mediated synthesis of isoxasoles from aldoximes.</p> Full article ">Scheme 50
<p>Obtaining 1,3-disubstituted pyrazoles by [3 + 2]-cycloaddition.</p> Full article ">Scheme 51
<p>Synthesis of 3<span class="html-italic">H-</span>pyrazole derivatives of diazoalkane dipole complexes.</p> Full article ">Scheme 52
<p>Three-component cycloaddition with acetylene.</p> Full article ">Scheme 53
<p>Cobalt-catalyzed [2 + 2 + 2]-cycloaddition.</p> Full article ">Scheme 54
<p>Trofimov reaction.</p> Full article ">Scheme 55
<p>A modified procedure for obtaining 3-alkyl-2-phenyl-1-vinylpyrroles.</p> Full article ">Scheme 56
<p>Synthesis of 3-(<span class="html-italic">E</span>)-styrylpyrroles from (<span class="html-italic">E</span>)-styrylmethyl ketoximes.</p> Full article ">Scheme 57
<p>Trofimov heterocyclization of bifenyl-derived oximes.</p> Full article ">Scheme 58
<p>Synthesis of 2-arylpyrroles with calcium carbide and water.</p> Full article ">Scheme 59
<p>Reaction of acetylene with ketoximes.</p> Full article ">Scheme 60
<p>Reaction of acetylene and ketones.</p> Full article ">Scheme 61
<p>Plausible mechanism of acetylene and ketones reaction.</p> Full article ">Scheme 62
<p>Cascade cyclization of ketones with acetylene under superbase conditions.</p> Full article ">Scheme 63
<p>Calcium carbide-based synthesis of benzofuran derivatives.</p> Full article ">Scheme 64
<p>Mechanism of benzofuran formation.</p> Full article ">Scheme 65
<p>Pd-catalyzed amine/aldehyde/acetylene reaction.</p> Full article ">Scheme 66
<p>Proposed mechanism of three component coupling.</p> Full article ">Scheme 67
<p>Synthesis of fluoroxene by trifluoroethanol vinylation.</p> Full article ">Scheme 68
<p>Two-step fluoroxene synthesis.</p> Full article ">Scheme 69
<p>The Favorskii reaction general scheme.</p> Full article ">Scheme 70
<p>Ethchlorvynol synthesis.</p> Full article ">Scheme 71
<p>Terpene synthesis with acetylene.</p> Full article ">Scheme 72
<p>Synthesis of 17-ethynylestradiol and quinestrol.</p> Full article ">Scheme 73
<p>Synthesis of mestranol by Favorskii reaction.</p> Full article ">Scheme 74
<p>Synthesis of desogestrel.</p> Full article ">Scheme 75
<p>Eplerenone precursor synthesis by Favorskii reaction.</p> Full article ">Scheme 76
<p>Synthesis and 3D representations of symmetrical bis-alkynyl derivative <b>141</b>. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are set at 30% probability. ’ = 1 − x, 1 − y, z; ’’ = y, 1 − x, −z; ’’’ = 1 − y, x, −z. (Reproduced with permission from ref. [<a href="#B180-molecules-23-02442" class="html-bibr">180</a>]. Copyright 2016 the Royal Society of Chemistry.).</p> Full article ">Scheme 77
<p>A mechanism proposed for the formation of acetylene-alkenyl complexes.</p> Full article ">Scheme 78
<p>Reaction of Au and Pt complexes with acetylene.</p> Full article ">Scheme 79
<p>Pt-catalyzed selective hydroarylation.</p> Full article ">Scheme 80
<p>Preparation of Ir-based vinyl and styryl compounds.</p> Full article ">Scheme 81
<p>Synthesis of [(<span class="html-italic">η</span><sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Ir(C^P)]<sup>+</sup> acetylene adduct and its thermal transformation.</p> Full article ">Scheme 82
<p>Acetylene insertion into deuterated tungsten complex.</p> Full article ">Scheme 83
<p>Synthesis of (<span class="html-italic">E</span>)-2-bromovinyltellurium tribromide.</p> Full article ">Scheme 84
<p>Pt(IV)-catalyzed addition of iodomethane to acetylene.</p> Full article ">Scheme 85
<p>A mechanism proposed for the formation of dppe oxide.</p> Full article ">Scheme 86
<p>Pt(II)-catalyzed addition of acrolein to acetylene in the presence of LiBr.</p> Full article ">Scheme 87
<p>Synthesis of (4<span class="html-italic">E</span>,6<span class="html-italic">Z</span>,10<span class="html-italic">Z</span>)-hexadeca-4,6,10-trien-1-ol <b>161</b> and (4<span class="html-italic">E</span>,6<span class="html-italic">E</span>,10<span class="html-italic">Z</span>)-hexadeca-4,6,10-trien-1-ol <b>162</b>.</p> Full article ">Scheme 88
<p>Acetylene carboxylation in the presence of TBD.</p> Full article ">Scheme 89
<p>A mechanism proposed for the TBD-promoted formation of acetylene dicarboxylic acid derivatives.</p> Full article ">Scheme 90
<p>Three component synthesis of enaminones.</p> Full article ">Scheme 91
<p>[2 + 2]-Cycloaddition of acetylene to pentafluorophenyltris(trimethylsilyl)cyclobutadiene.</p> Full article ">Scheme 92
<p>Synthesis of polystannanes with –CH=CH– link.</p> Full article ">Scheme 93
<p>Reaction possibilities of acetylene hydrogenation.</p> Full article ">Scheme 94
<p>Acetylene hydrochlorination.</p> Full article ">Scheme 95
<p>Phenylacetylene polymerization.</p> Full article ">
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