Dodecahedrane: Difference between revisions

| Watchedfields = changed

| verifiedrevid = 445325696

| ImageFile = [[File:Dodecahedrane.svg|80px]]

| ImageFileL1 = Dodecahedrane-3D-sticks.png

| ImageFileR1 = Dodecahedrane-3D-vdW.png

| IUPACName = (C₂₀-''I''_h)[5]fullerane<br/>hexadecahydro-1,6,5,2,4,3-(epibutane[1,1,2,3,4,4]hexayl)dipentaleno[2,1,6-''gha'':2′,1′,6′-''cde'']pentalene

| SystematicName = undecacyclo[9.9.0.0^2,9.0^3,7.0^4,20.0^5,18.0^6,16.0^8,15.0^10,14.0^12,19.0^13,17]icosane

| Section1 = {{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 4493-23-6

| Beilstein = 1880116

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 33013

| Gmelin = 1326921

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = FBO87C776P

| PubChem = 123218

| SMILES1 = C31C%10C2C5C%11C6C8C(C1C9C4C7C(C2C34)C5C6C7C89)C%10%11

| Section2 = {{Chembox Properties

| C=20 | H=20

| MeltingPt =430±10°C

| MeltingPt_ref=<ref>{{Cite book | url=https://books.google.com/books?id=r0s-xE-Ym0gC&q=dodecahedrane+melting+point+430&pg=PA199 | title=Strategies and Tactics in Organic Synthesis| isbn=9780323152938| date=2012-12-02| last1=Lindberg| first1=Thomas}}</ref>

| Section3 = {{Chembox Hazards

| AutoignitionPt =

| Section8 = {{Chembox Related

| OtherFunction = [[Cubane]]<br>[[Tetrahedrane]]<br>[[Pagodane]] (an isomer of dodecahedrane)<br>[[Prismane]]

| OtherFunction_label = [[hydrocarbon]]s

'''Dodecahedrane''' is a [[chemical compound]], a [[hydrocarbon]] with formula {{chem2|C20H20}}, whose [[carbon]] atoms are arranged as the vertices (corners) of a regular [[dodecahedron]]. Each carbon is [[covalent bond|bound]] to three neighbouring carbon atoms and to a [[hydrogen]] atom. This compound is one of the three possible [[Platonic hydrocarbons]], the other two being [[cubane]] and [[tetrahedrane]].

Dodecahedrane does not occur in nature and has no significant uses. It was synthesized by [[Leo Paquette]] in 1982, primarily for the "aesthetically pleasing [[molecular symmetry|symmetry]] of the dodecahedral framework".<ref name=paquette1982/>

For many years, dodecahedrane was the simplest real carbon-based [[molecule]] with full [[icosahedral symmetry]]. [[Buckminsterfullerene]] ({{chem2|C60}}), discovered in 1985, also has the same symmetry, but has three times as many carbons and 50% more atoms overall. The synthesis of the [[C20 fullerene|C₂₀ fullerene]] {{chem2|C20}} in 2000, from [[bromine|brominated]] dodecahedrane,<ref name=prinz2000/> may have demoted {{chem2|C20H20}} to second place.

==Structure==

The angle between the C-C bonds in each carbon atom is 108°, which is the angle between adjacent sides of a [[regular pentagon]]. That value is quite close to the 109.5° [[central angle]] of a [[regular tetrahedron]]—the ideal angle between the bonds on an atom that has sp³ [[orbital hybridisation|hybridisation]]. As a result, there is minimal [[angle strain]]. However, the molecule has significant levels of [[Strain (chemistry)#Torsional strain|torsional strain]] as a result of the [[eclipsed conformation]] along each edge of the structure.<ref>{{cite journal|first=Leo|last=Paquette|title=Dodecahedrane-The chemical transliteration of Plato's universe (A Review)|date=1982|journal=[[Proc Natl Acad Sci U S A]]|volume=79|issue=14|pages=4495–4500|doi=10.1073/pnas.79.14.4495|bibcode=1982PNAS...79.4495P|doi-access=free|pmc=346698}}</ref>

The molecule has perfect icosahedral (I_h) [[molecular symmetry|symmetry]], as evidenced by its [[proton NMR]] spectrum in which all hydrogen atoms appear at a single [[chemical shift]] of 3.38&nbsp;ppm. Unlike buckminsterfullerene, dodecahedrane has no [[delocalized electron]]s and hence has no [[aromaticity]].

==History==

For over 30 years, several research groups actively pursued the [[total synthesis]] of dodecahedrane. A review article published in 1978 described the different strategies that existed up to then.<ref name=eaton1979/> The first attempt was initiated in 1964 by [[Robert Burns Woodward|R.B. Woodward]] with the synthesis of the compound [[triquinacene]] which was thought to be able to simply dimerize to dodecahedrane. Other groups were also in the race, for example that of [[Philip Eaton]] and [[Paul von Ragué Schleyer]].

Leo Paquette's group at [[Ohio State University]] was the first to succeed, by a complex 29-step route that mostly builds the dodecahedral skeleton one ring at a time, and finally closes the last hole.<ref name=paquette1982/>

In 1987, more versatile alternative synthesis route was found by the [[Horst Prinzbach]]'s group.<ref name=fessner/><ref name=bulusu/> Their approach was based on the isomerization [[pagodane]], obtained from isodrin (isomer of [[aldrin]]) as starting material i.a. through [6+6][[cycloaddition|photocycloaddition]]. Schleyer had followed a similar approach in his synthesis of [[adamantane]].

Following that idea, joint efforts of the Prinzbach team and the Schleyer group succeeded but obtained only 8% yield for the conversion at best. In the following decade the group greatly optimized that route, so that dodecahedrane could be obtained in multi-gram quantities. The new route also made it easier to obtain derivatives with selected substitutions and [[Saturated and unsaturated compounds|unsaturated carbon-carbon bonds]]. Two significant developments were the discovery of [[σ-bishomoaromaticity]]<ref name=prakash/> and the formation of [[C20 fullerene|C₂₀ fullerene]] from highly brominated dodecahedrane species.<ref name=prinz2000/><ref name=prinz2006/>

==Synthesis==

===Original route===

Paquette's 1982 [[organic synthesis]] takes about 29 steps with raw materials [[cyclopentadiene]] (2 equivalents 10 carbon atoms), [[dimethyl acetylenedicarboxylate]] (4 carbon atoms) and [[allyltrimethylsilane]] (2 equivalents, 6 carbon atoms).

In the first leg of the procedure <ref name=paquette1974/> two molecules of [[cyclopentadiene]] '''1''' are [[coupling reaction|coupled]] together by reaction with elemental [[sodium]] (forming the [[cyclopentadienyl complex]]) and [[iodine]] to [[fulvalene|dihydrofulvalene]] '''2'''. Next up is a [[tandem reaction|tandem]] [[Diels–Alder reaction]] with [[dimethyl acetylenedicarboxylate]] '''3''' with desired sequence pentadiene-acetylene-pentadiene as in symmetrical adduct '''4'''. An equal amount of asymmetric pentadiene-pentadiene-acetylene compound ('''4b''') is formed and discarded.

:{|align="center" class="wikitable" style="font-size:small"

|valign=top |[[Image:DodecahedraneSynthesisStepII.png|350px|Dodecahedrane synthesis part I]]

| Dodecahedrane synthesis part I||Dodecahedrane synthesis part II

In the next step of the sequence <ref name=wyvratt/> iodine is temporarily introduced via an [[iodolactonization]] of the diacid of '''4''' to dilactone '''5'''. The [[ester]] group is cleaved next by [[methanol]] to the [[halohydrin]] '''6''', the [[Alcohol (chemistry)|alcohol]] groups converted to [[ketone]] groups in '''7''' by [[Jones oxidation]] and the iodine groups reduced by a [[zinc-copper couple]] in '''8'''.

:{|align="center" class="wikitable" style="font-size:small"

|valign=top |[[Image:DodecahedraneSynthesisPartIV.png|350px|Dodecahedrane synthesis part IV]]

| Dodecahedrane synthesis part III||Dodecahedrane synthesis part IV

The final 6 carbon atoms are inserted in a [[nucleophilic addition]] to the ketone groups of the [[carbanion]] '''10''' generated from [[allyltrimethylsilane]] '''9''' and [[N-Butyllithium|''n''-butyllithium]]. In the next step the [[vinyl silane]] '''11''' reacts with [[peracetic acid]] in [[acetic acid]] in a [[radical substitution]] to the dilactone '''12''' followed by an [[Intramolecular reaction|intramolecular]] [[Friedel-Crafts alkylation]] with [[phosphorus pentoxide]] to diketone '''13'''. This molecule contains all required 20 carbon atoms and is also symmetrical which facilitates the construction of the remaining 5 [[carbon-carbon bond]]s.

Reduction of the [[double bond]]s in '''13''' to '''14''' is accomplished with [[hydrogenation]] with [[palladium on carbon]] and that of the ketone groups to alcohol groups in '''15''' by [[sodium borohydride]]. Replacement of hydroxyl by [[chlorine]] in '''17''' via [[nucleophilic aliphatic substitution]] takes place through the dilactone '''16''' ([[tosyl chloride]]). The first C–C bond forming reaction is a kind of [[Birch alkylation]] ([[lithium]], [[ammonia]]) with the immediate reaction product trapped with [[chloromethyl phenyl ether]],<ref name=Paquette/> the other chlorine atom in '''17''' is simply reduced. This temporary appendix will in a later stage prevent unwanted [[enolization]]. The newly formed [[ketone]] group then forms another C–C bond by [[photochemical]] [[Norrish reaction]] to '''19''' whose alcohol group is induced to [[elimination reaction|eliminate]] with [[TsOH]] to [[alkene]] '''20'''.

:{|align="center" class="wikitable" style="font-size:small"

|valign=top |[[Image:DodecahedraneSynthesisPartVI.png|350px|Dodecahedrane synthesis part VI]]

| Dodecahedrane synthesis part V||Dodecahedrane synthesis part VI

The double bond is reduced with [[hydrazine]] and sequential [[diisobutylaluminum hydride]] reduction and [[pyridinium chlorochromate]] oxidation of '''21''' forms the [[aldehyde]] '''22'''. A second Norrish reaction then adds another C–C bond to alcohol '''23''' and having served its purpose the phenoxy tail is removed in several steps: a [[Birch reduction]] to diol '''24''', oxidation with [[pyridinium chlorochromate]] to ketoaldehyde '''25''' and a reverse [[Claisen condensation]] to ketone '''26'''. A third Norrish reaction produces alcohol '''27''' and a second [[Dehydration reaction|dehydration]] '''28''' and another reduction '''29''' at which point the synthesis is left completely without [[functional group]]s. The missing C-C bond is put in place by hydrogen pressurized [[dehydrogenation]] with [[palladium on carbon]] at 250&nbsp;°C to dodecahedrane '''30'''.

===Pagodane route===

In Prinzbach's optimized route from pagodane to dodecahedrane, the original low-yielding isomerization of parent pagodane to dodecahedrane is replaced by a longer but higher yielding sequence - which nevertheless still relies heavily on pagodane derivatives. In the scheme below, the divergence from the original happens after compound 16.

:[[File:Optimized Dodecahedrane Synthesis en.png|thumb|left|800px|Optimized route to dodecahedrane]]

{{clear}}

A variety of dodecahedrane derivatives have been synthesized and reported in the literature.

===Hydrogen substitution===

Substitution of all 20 hydrogens by [[fluorine]] atoms yields the relatively unstable [[perfluorododecahedrane]] C₂₀F₂₀, which was obtained in milligram quantities. Trace amounts of the analogous [[perchlorododecahedrane]] C₂₀Cl₂₀ were obtained, among other partially chlorinated derivatives, by reacting {{chem2|C20H20}} dissolved in liquid [[chlorine]] under pressure at about 140&nbsp;°C and under intense light for five days. Complete replacement by heavier [[halogen]]s seems increasingly difficult due to their larger size. Half or more of the hydrogen atoms can be substituted by [[hydroxyl]] groups to yield [[polyols]], but the extreme compound C₂₀(OH)₂₀ remained elusive as of 2006.<ref name=prinz20062/> Amino-dodecahedranes comparable to [[amantadine]] have been prepared, but were more toxic and with weaker antiviral effects.<ref>Weber JC, Paquette LA. Synthesis of amino-substituted dodecahedranes, secododecahedranes, and homododecahedranes, and their antiviral relationship to 1-aminoadamantane. ''J. Org. Chem''. 1988; 53(22): 5315-5320. {{doi|10.1021/jo00257a021}}</ref>

[[Annulation|Annulated]] dodecahedrane structures have been proposed.<ref name=banfalvia/><ref name=liu/>

===Encapsulation===

Molecules whose framework forms a closed cage, like dodecahedrane and buckminsterfullerene, can encapsulate atoms and small molecules in the hollow space within. Those insertions are not chemically bonded to the caging compound, but merely mechanically trapped in it.

Cross, Saunders and Prinzbach succeeded in encapsulating [[helium]] atoms in dodecahedrane by shooting He⁺ ions at a film of the compound. They obtained [[microgram]] quantities of He@{{chem2|C20H20}} (the "@" being the standard notation for encapsulation), which they described as a quite stable substance.<ref name=cross/> The molecule has been described as "the world's smallest [[helium balloon]]".<ref>{{cite book|author1=Putz, Mihai V.|author2=Mirica, Marius Constantin|title=Sustainable Nanosystems Development, Properties, and Applications|url=https://books.google.com/books?id=o7nLDAAAQBAJ|date=2016|publisher=IGI Global|isbn=978-1-5225-0493-1|chapter=4|page=124}}</ref>

{{reflist|colwidth=30em

|refs=

<ref name=paquette1982>{{cite journal|title=Dodecahedrane

|first1=Robert J.|last1= Ternansky|first2= Douglas W.|last2= Balogh|first3= Leo A.|last3= Paquette

|journal=[[J. Am. Chem. Soc.]] |date=1982 |volume=104|issue=16 |pages=4503–4504 |doi=10.1021/ja00380a040}}

</ref><ref name=Paquette>{{cite journal

| first1= Leo A. |last1=Paquette|first2= Robert J.|last2= Ternansky|first3= Douglas W.|last3= Balogh|first4= Gary|last4= Kentgen

| year = 1983

| title = Total synthesis of dodecahedrane

| journal = [[J. Am. Chem. Soc.]]

| volume = 105

| issue = 16

| pages = 5446–5450

| doi =10.1021/ja00354a043}}</ref>

<ref name=eaton1979>{{cite journal|title=Towards dodecahedrane|journal=[[Tetrahedron (journal)|Tetrahedron]]|volume=35|issue=19|date=1979|pages=2189–2223|first= Philip E.|last= Eaton |doi=10.1016/0040-4020(79)80114-3}}</ref>

<ref name=paquette1974>{{cite journal|title=Domino Diels–Alder reactions. I. Applications to the rapid construction of polyfused cyclopentanoid systems|first1=Leo A.|last1=Paquette |first2=Matthew J. |last2=Wyvratt |journal=[[J. Am. Chem. Soc.]]|date=1974|volume=96|issue=14|pages=4671–4673|doi=10.1021/ja00821a052}}</ref>

<ref name=wyvratt>{{cite journal|title=Topologically spherical molecules. Synthesis of a pair of C₂-symmetric hexaquinane dilactones and insights into their chemical reactivity. An efficient π-mediated 1,6-dicarbonyl reduction|first1=Leo A.|last1= Paquette|first2= Matthew J.|last2= Wyvratt|first3= Otto|last3= Schallner|first4= Jean L.|last4= Muthard|first5= William J.|last5= Begley|first6= Robert M.|last6= Blankenship|first7=Douglas|last7= Balogh |journal=[[J. Org. Chem.]]|date=1979|volume=44|issue=21|pages=3616–3630|doi=10.1021/jo01335a003}}</ref>

<ref name=fessner>{{cite journal|first1=Wolf-Dieter |last1=Fessner |first2=Bulusu A. R. C. |last2=Murty |first3=Horst |last3=Prinzbach |date=1987|title=The Pagodane Route to Dodecahedranes – Thermal, Reductive, and Oxidative Transformations of Pagodanes |journal=[[Angew. Chem. Int. Ed. Engl.]]| volume=26 |issue=5 |pages=451–452 |doi=10.1002/anie.198704511}}</ref>

<ref name=bulusu>{{cite journal|first1=Wolf-Dieter |last1=Fessner |first2=Bulusu A. R. C. |last2=Murty |first3=Jürgen |last3=Wörth |first4=Dieter |last4=Hunkler |first5=Hans |last5=Fritz |first6=Horst |last6=Prinzbach |first7=Wolfgang D. |last7=Roth|first8=Paul von Ragué |last8=Schleyer |first9=Alan B. |last9=McEwen|first10= Wilhelm F.|last10= Maier |date=1987 |title=Dodecahedranes from [1.1.1.1]Pagodanes|journal=[[Angew. Chem. Int. Ed. Engl.]]| volume=26 |issue=5 |pages=452–454 |doi=10.1002/anie.198704521}}

</ref>

<ref name=prakash>{{cite journal|first1=G. K. S.|last1=Prakash|first2=V. V.|last2=Krishnamurthy|first3=R.|last3=Herges|first4=R.|last4=Bau|first5=H.|last5=Yuan|first6=G. A.|last6=Olah|first7=W.-D.|last7=Fessner|first8=H.|last8=Prinzbach|title=[1.1.1.1]- and [2.2.1.1]Pagodane Dications: Frozen Two-Electron Woodward–Hoffmann Transition State Models|journal=[[J. Am. Chem. Soc.]]|date=1988|volume=110|issue=23|pages=7764–7772|doi=10.1021/ja00231a029}}</ref>

<ref name=prinz2000>{{cite journal|first1=Horst |last1=Prinzbach|first2= Andreas|last2= Weiler|first3= Peter |last3=Landenberger|first4= Fabian |last4=Wahl|first5= Jürgen|last5= Wörth|first6= Lawrence T. |last6=Scott|first7= Marc |last7=Gelmont|first8= Daniela|last8= Olevano|first9= Bernd von |last9=Issendorff|title=Gas-phase production and photoelectron spectroscopy of the smallest fullerene, C₂₀|journal=[[Nature (journal)|Nature]]|volume=407|issue=6800|pages=60–63|date=7 September 2000 | doi=10.1038/35024037|pmid=10993070|bibcode=2000Natur.407...60P|s2cid=4355045}}</ref>

<ref name=prinz2006>{{cite journal|first1=H.|last1= Prinzbach|first2= F.|last2= Wahl|first3= A.|last3= Weiler|first4= P.|last4= Landenberger|first5= J. |last5=Wörth|first6= L. T.|last6= Scott|first7= M.|last7= Gelmont|first8= D.|last8= Olevano|first9= F.|last9= Sommer|first10=B. von|last10=Issendorff|title= C₂₀ Carbon Clusters: Fullerene–Boat–Sheet Generation, Mass Selection, PE Characterization|journal=[[Chem. Eur. J.]]|date= 2006|volume= 12|issue= 24|pages= 6268–6280|doi= 10.1002/chem.200501611|pmid= 16823785}}</ref>

<ref name=cross>{{cite journal|first1=R. James|last1= Cross|first2= Martin|last2= Saunders|first3=Horst |last3=Prinzbach |date=1999 |title=Putting Helium Inside Dodecahedrane |journal=[[Org. Lett.]]|volume= 1|issue= 9 |pages= 1479–1481 |doi=10.1021/ol991037v}}</ref>

<ref name=prinz20062>{{cite journal|first1=Fabian|last1= Wahl|first2= Andreas |last2=Weiler|first3= Peter|last3= Landenberger|first4= Emmerich|last4= Sackers|first5= Torsten |last5=Voss |first6=Alois |last6=Haas|first7= Max |last7=Lieb|first8= Dieter|last8= Hunkler|first9= Jürgen |last9=Wörth

|first10=Lothar |last10=Knothe|first11= Horst |last11=Prinzbach |date=2006 |title=Towards Perfunctionalized Dodecahedranes—En Route to C₂₀ Fullerene|journal=Chem. Eur. J. |volume=12 |issue= 24|pages=6255–6267 |doi=10.1002/chem.200501618|pmid= 16807931}}</ref>

<ref name=banfalvia>{{cite journal|title=Dodecahedrane minibead polymers|first= Gaspar|last= Banfalvia |journal= RSC Adv. |date=2014|volume=4 |issue= 6|pages=3003–3008 |doi=10.1039/C3RA43628D|bibcode= 2014RSCAd...4.3003B}}</ref>

<ref name=liu>{{cite journal|title=DFT study on a molecule C₂₅H₂₀ with a dodecahedrane cage and a pentaprismane cage sharing the same pentagon|first1= Feng-Ling|last1= Liu |journal=J. Mol. Struct.: Theochem |volume=681 |issue=1–3 |date=26 July 2004 |pages= 51–55 |doi=10.1016/j.theochem.2004.04.051}}</ref>

}}

* [http://www.synarchive.com/syn/15 Paquette's dodecahedrane synthesis at SynArchive.com]

* [https://web.archive.org/web/20110522025444/http://www.wikinfo.org/index.php/2D_and_3D_Models_of_Dodecahedrane_and_Cuneane_Assemblies 2D and 3D models of dodecahedrane and cuneane assemblies]

* [http://www.pnas.org/content/79/14/4495.full.pdf Full text of Paquette's paper]

[[Category:Polycyclic nonaromatic hydrocarbons]]

[[Category:Cyclopentanes]]

[[Category:Substances discovered in the 1980s]]