SE127240C1 - - Google Patents

Description

Inventor: R. R. Whetstone.

Priority was given on April 11, 1947 (United States States).

The invention relates to a process for producing cyclopentanecarboxamide hydrides and derivatives thereof. More particularly, the invention relates to a process for the preparation of cyclopentane-carboxaldehydes and derivatives thereof, which comprises catalytic dehydration of a tetrahydropyran-2-methanol in the off-phase to form a cyclopentane-carboxaldehyde containing the same number of carbon atoms as the tetrahydropyran-2-methanol. The cyclopentane-carboxacyl hydride thus prepared can be optionally converted into various derivatives thereof or, according to an embodiment of the invention, the conversion, e.g. by hydrogenation, at least in part simultaneously with the dehydration step of the process.

The process according to the invention is generally applicable to the conversion of tetrahydropyran-2-methanols, which can be brought about under the conditions prevailing in the process, into cyclopentanecarboxaldehydes, which have the same number of carbon atoms as the other tetrahydropyran-2-methanol. Thus, the general terms Rrt tetrahydropyran-2-methanob and tetrahydropyran-2-methanols are used, by which are meant derivatives of tetrahydropyran which have a methanol group (eg a hydroxymethyl group) directly attached to a carbon atom which is attached thereto. to the heterocyclic oxygen atom in the tetrahydropyran ring.

The tetrahydropyran ring may have attached to it only the methanol substituent group, as is the case with the specific compound tetrahydropyran-2-methanol, or it may contain substituent groups in addition to the methanol group. Such substituent groups may be, for example, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, alkenyl, cycloalkenyl, alkenaryl, aralkenyl, or the like. The process of the invention is used to advantage for the conversion of tetrahydropyran-2-methanols, which contain only relatively joke reactive substituent groups or no such groups beyond the methanol group. The invention was subsequently used aptly for the conversion of such tetrahydropyran-2-methanols, which contain only matte and / or aromatic bonds of carbon to carbon, in other words, to the conversion of tetrahydropyran-2-methanol and its carnally alkyl- and / or aryl-substituted products. Among the conversions which fall within the scope of the invention are, for example, tetrahydropyran-2-methanol to cyclopentanecarboxaldehyde; 2,6-dimethyltetrahydropyran-2-methanol to dimethylcyclopentanecarboxaldehyde; 3,4-dimethyltetrahydropyran-2-methanol to dimethylcyclopentane - carboxaldehyde; 5-methyltetrahydropyran-2-methanol to methylcyclopentanecarboxaldehyde; 2,5-diethyltetrahydropyran-2-methanol to diethylcyclopentanecarboxaldehyde; 3,4-dipropylethetrahydropyran-2-methanol to dipropyl-cyclopentanecarboxaldehyde; 2-methyl-5-ethylLetrapyran-2-methanol to methylethylcyclopentanecarboxaldehyde; phenyltetrahydropyran-2-methanol to phenycyclapentanecarboxaldehyde; 3-cyclohexyltetrahydropyran-2-methanol to cyclohexylcyclopentanecarboxaldehyde; 3-phenyl-4-methyl-tetrahydropyran-2-methanol to methylphenycyclopentanecarboxamide, and conversions of analogous and homologous substituted tetrahydropyran-2-methanols to substituted cyclopentanecarboxaldehydes.

It is convenient to prepare tetrahydropyran-2-methanols which can be converted according to the invention into the corresponding cyclopentanecarboxaldehydes, e.g. tetrahydropyran-2-methanol and in carnan alkyl-substituted products thereof, consists in subjecting an α43-olefinically unsaturated aldehyde such as acrolein or one of its home layers, preferably one of its β-methylene homologues, to an elevated temperature in the presence of a polymerization preventing agent to effect condensation or "dimerization" of the aldehyde to a compound in the 3-4-dihydro-1,2-dihydro-1,2-pyran-2-carboxyhydrogen series. For example, a solution of acrolein or of homologous α, β-unsaturated aldehyde in approximately equal weight of benzene, containing about 1% hydroquinone, shaved pit the aldehyde weight, can be heated to about 170 ° C for several hours and under a pressure, which is Lillrdekligt to keep the mixture in liquid form. At the end of this time period, one can recover from the mixture, e.g. by fractional 2 - - destination dihydropyran-carboxaldehyde formed by the condensation of the unsaturated aldehyde. The dihydro-pyran-carboxaldehyde can be rapidly converted by hydrogenation to the corresponding tetrahydropyran-2-methanol. The hydrogenation can be carried out so that the dihydropyran ring is matted and the formyl group is reduced to a hydroxymethyl group in one and the same step. A Raney nickel catalyst is, among other things, suitable as a catalyst during hydrogenation. Relatively strict hydrogenation conditions must be used, e.g. temperatures during the hydrogenation exceeding ° C and water pressure above about kg / cm '. The presence of a solvent, & Isom methanol, during the treatment with water here also has a beneficial effect on the conversion to tetrahydropyran2-methanol. After completion of the hydrogenation and removal of the catalyst and solvent, the tetrahydropyran-2-methanol can be purified, e.g. by fractional distillation, before it is used in the process according to the invention or, if desired, the less pure mixture can be treated in its entirety according to the invention. It will be readily appreciated that other methods may be used for the preparation of the tetrahydropyran-2-methanol to which the method of the invention is applied, and that the invention therefor be construed as being limited to the particular representatives of the class defined herein. of tetrahydropyran-2-methanols, which can be prepared from α, β-olefinically unsaturated aldehydes as described above.

As catalyst in the present process, one or more of the materials commonly known in the art may be used, dehydration catalysts, i.e., the substances which have been capable of catalytically promoting dehydration of organic compounds by cleavage of water from the organic molecule with or without simultaneous rearrangement of the molecular skeleton of the molecule. The catalyst which can be used in the present process is a solid dehydration catalyst of an inorganic nature. One group of the substances belonging to such catalysts comprises the oxides of polyvalent metals, belonging to groups II, III, and. IV in the periodic table. This group includes, for example, the divalent metal oxides, such as zinc oxide, magnesium oxide and calcium oxide, and oxides of metals, which may have higher valence numbers than 2, such as alumina, thorium oxide, lead, silica, dtan oxide and ceroxide. The substances that can be transformed during the conditions prevailing during the process, e.g. by dehydration, to catalytically active metal oxide or mixture of oxides, such as hydrates of the said oxides, the said group of useful catalysts also fall.

Inorganic salts, which can act as dehydration catalysts, can also be used in the process according to the invention. Such salts may be acidic, neutral or basic. Inorganic salts, which are active as dehydration catalysts, include phosphates, silicates, halides, aluminates and other active salts of the polyvalent metals in groups II, III and IV of the Periodic Table. The term dosages »includes Avg orthophosphates as metaphosphates. Among the phosphates of polyvalent metals are calcium phosphates, basic aluminum phosphate, magnesium phosphate, lead phosphate, calcium magnesium phosphate, etc. Complex acid phosphates, for example the phosphoric acid catalyst formed by calcination of a mixture of phosphoric acid and silica phosphoric acid catalyst »can also be used as a catalyst. (In the usual commercial form, the solid phosphoric acid catalyst may give rise to strong side reactions, if used without prior modifying treatment. In such cases, its usefulness to the process may be improved by a prior treatment with superheated effect to reduce or modify its catalytic activity) . Other salts which are active as dehydration catalysts and which can be used in the process of the invention are, for example, calcium sulphate, zinc sulphate, aluminum sulphate, thorium sulphate, lead sulphate, zinc chloride, iron chloride, nickel sulphate and the like.

The catalytically active complex inorganic polyacids, such as silicon tungstic acid, silicon vanadic acid, titanium molybdic acid, manganese molybdic acid and the like, can also be used as dehydration catalysts.

The dehydration catalyst may consist exclusively of a catalytically active compound or it may be a mixture of two or more such compounds. Mixtures of tips, mechanical or chemically combined mixtures of metal oxides, mixtures of salts or mixtures of a metal oxide with a catalytically active metal salt can also be used. For example, a metal oxide, such as alumina, may be mixed with an oxide of another metal or a salt of cii metal, the second component per se being catalytically active or optionally serving to increase or modify the activity of the primary catalyst in the underlying process.

Although a large number of substances which are active as dehydration catalysts can be used in the process according to the invention, it is generally most convenient to use one of the above-mentioned metal values. With regard to cost and efficiency, it is particularly appropriate to use an alumina as a dehydration catalyst which has the properties which characterize activated alumina, i.e. an adsorptive alumina, which predominantly consists of α-monohydrate of alumina and / or γ-alumina. Such activated or adsorptive aluminas can be characterized as being substantially soluble in dilute mineral acids as opposed to non-adsorptive aluminas, which are relatively insoluble in such acids. The activated aluminas which are suitable for the present process can either be synthetically activated aluminas or be produced from naturally occurring aluminas or minerals which are rich in aluminum hydrate, e.g. bauxite, diaspora or hydrargillite. Activated aluminas, which are suitable for the practice of the present invention, may also be prepared by treating synthetic alumina gels, by treating a crystalline material, such as crystalline (aluminum trihydrate, which crystallized from alkaline aluminates, or by other processes, such as via skilled in the art, for the preparation of activated or adsorptive aluminas.

According to one embodiment of the invention, the catalyst may contain, in addition to the component which is active as a dehydration catalyst, a second component which may be active as a hydrogenation catalyst. The process leading to the dehydration of the tetrahydropyran-2-methanol can thus be carried out in the presence of hydrogen chloride and a hydrogenation catalyst, whereby a partial or complete reduction of the cyclopentanecarboxaldehyde to the corresponding cyclopentanemethanol is effected simultaneously with its formation in the same reaction system. . Depending on the particular dehydration catalyst used, the hydrogenation catalyst may be mechanically mixed with the dehydration catalyst or the latter may be coated, impregnated or otherwise combined with the hydrogenation catalyst to obtain an intimate catalyst mixture which catalytically activates dehydration for dehydration. The dehydration catalyst may contain, in addition to one or more of the said dehydration catalysts, any of the hydrogenation catalysts used in the catalytic reduction technique of organic compounds, such as a free metal hydrogenation catalyst or an active metal compound. In some cases, one and the same metal oxide may be active both as a dehydration catalyst and as a hydrogenation catalyst. Among the hydrogenation catalysts which can be used in this way are mentioned the free metals Pt, Ni, Pd, Au, Co, Fe, Cu, Ag, Mo, Cr, W, Mn and mixtures thereof as well as compounds of these metals, as their oxides and. sulfides. An efficient dehydration-hydration catalyst can be prepared, for example, by impregnating activated alumina with dilute chromic acid and drying the resulting pulp. Other suitable dehydration-hydration catalysts can be prepared in a similar manner.

The dehydration of the tetrahydropyran-2-methanol can be accomplished by contacting it in angular form with the dehydration catalyst at elevated temperature and for an appropriate period of time. Any suitable apparatus can be used for carrying out the process, although the process should be carried out in an apparatus which tampers itself for continuous work. A stream of the tetrahydropyran-2-methanol was thus placed in contact with the dehydration catalyst, which is placed in a suitable, heated reaction tube, at a temperature () eh at a feed rate which is favorable for the desired dehydration reaction. The dehydration reaction is favored by reaction temperatures of about 250 ° C or higher and preferably at least about 270 ° C. Significantly higher temperatures can be used, up to temperatures which cause a strong thermal probe division of the organic material used. Temperatures up to 550 ° C can often be used. The lightest temperature range Jigger between. about 300 ° C and about 450 ° C.

The feed rate of the tetrahydrapyran-2-methanol can be varied within wide limits, depending on the particular catalyst used, the reaction temperature and the conversion desired for each passage. contact with a volume unit of the catalyst. Expressed in these units, supply rates of from 0.1 to about 1.5 are generally satisfactory, but the most suitable speed range should be between about 0.5 and about 1.0. These values, however, are not particularly fixed, but alit depending on the circumstances, possibly higher or lower speeds may come into question.

The tetrahydropyran-2-methanol can be introduced into the reaction zone and / or in contact with the catalyst either in the liquid or in gaseous state. It can be evaporated in a preheater and a step of the vapor is locked in contact with the catalyst, or it can be introduced as a liquid directly into the reaction vessel or the reaction tube, the pre-angling entering at the contact of letrahydropyran-2-methanol with the heated the catalyst oeh / or the rocks of the reaction chamber. The process can be performed either at atmospheric pressure or at pressure Over or below atmospheric pressure. Optionally, a neutral gas, such as nitrogen, carbon dioxide or methane, may be mixed with the fumes of the tetrahydropyran-2-methanol which is contacted with the catalyst, or karma undiluted fumes of the tetrahydropyran-2-methanol may be brought into contact with the catalyst. If it is desired to achieve a simultaneous dehydration of the tetrahydropyran-2-methanol and reduction of the dehydration products, a gas mixture consisting of tetrahydropyran-2-methanol and vale can be contacted with a dehydration-hydrogenation catalyst of the above kind. The amount of hydrogen present in the gas mixture may be greater or less than the theoretically required amount to reduce the dehydration products, although a stone effect of the process is achieved by the presence of a moderate excess of hydrogen over the theoretically required amount. Based on the amount of tetrahydropyran-2-methanol, about 0.5 moles of hydrogen 4- or more can be advantageously used per mole of the tetrahydropyran-2-methanol. Oyer pressure p4 selection can be used.

The products formed by the present process can be recovered at any time from the gas mixture leaving the reaction tube. In addition to the cyclopentane carboxaldehyde formed by the dehydration and isomerization of the tetrahydropyran-2-methanol, other products may be present which may have arisen by side reactions or partial reactions during the process. Other products which may consist of carbonyl products, since the dehydration is carried out in the absence of free hydrogen, appear to include acyclic hydroxyaldehydes, unsaturated carbonyl compounds, heterocyclic carbonyl compounds and the like. For example, the dehydration of tetrahydropyran-2-methanol in the presence of aluminum phosphate or other dehydration catalysts and catalytic reduction of the resulting mixture have been found to lead to the formation of small amounts of hexamethylene glycol. This and other products formed in the process according to the invention constitute valuable products which are advantageously utilized and purified in a suitable manner.

The gas mixture leaving the reaction vessel can be condensed and the products separated by franked distillation, by treatment with selective solvents, by chemical aids or otherwise. The mixture of products obtained by the dehydration of a tetrahydropyran-2-methanol of the present class may sometimes be less likely to separate into its constituents, e.g. by fractional distillation to, for example, the corresponding mixture of hydrogenated dehydrated products. If it is desired to obtain hydrogenated products as final products, i.e. cyclopentane methanol, it is therefore advantageous to postpone the complete separation of the reaction mixture into its components until the hydrogenation is completely carried out.

The following examples serve to illustrate some of the numerous embodiments of the invention. The first example describes the use of the process for the preparation of cyclopentanecarboxaldehyde and its recovery in practically pure form by dehydration of tetrahydropyran-2-methanol. In some of the other examples, it was found more convenient to hydrate the crude mixture of dehydration products and separate the resulting hydroxyl compounds. It will be appreciated that the subsequent hydrogenation in these examples could be omitted and the cyclopentanecarboxaldehyde recovered from the dehydration mixture by methods similar to that used in the first example.

Example I. 165 cma activated type A alumina from the Aluminum Ore Company of America was placed in a stainless steel reaction tube which was 101 cm long and 1.7 cm in diameter. Gaseous tetrahydropyran-2-methanol was passed through the tube under atmospheric pressure at 430 to 4 ° C and at a feed rate corresponding to 0.88 liquid volumes per hour and per unit volume of the catalyst. The mixture, which reached the rudder, was passed through a water-cooled condenser. The condensed part was divided into two phases, an aqueous phase and an organic phase. Of 348 g of tetrahydropyran-2-methanol, 237 g of the organic phase and 101 g of the aqueous phase are obtained. A small amount of gas, which did not condense at the cooling water temperature, was formed.

The organic base was separated into free frail water and distilled. The fraction which evaporated at a temperature up to 1 ° C under atmospheric pressure was precipitated and the fraction which then distilled off to 68 ° C under a pressure of 15 mm Hg and 128 g was collected. Yid redistillation of this latter fraction yields 63 g of cyclopentanecarboxaldehyde, which distilled yid 135.9 to 138 ° C (distillation temperature according to the literature 136 ° C), had a refractive index (n 20 / D) of 1.4423 and formed a semicarbazone, which melted yid 120 to 122 ° C (literature number 123 to 124 ° C). An additional 40 g of less pure cyclopentanecarboxaldehyde was recovered as fractions, which distilled Over between 127 and 135.9 ° C and between 138 and 1 ° C.

Example II. 500 parts of tetrahydropyran-2-methanol were passed through the reaction tube of Example I, which contained fresh, activated alumina of the same kind as in Example I, at atmospheric pressure yid 320 to 340 ° C and at a tin feed rate corresponding to 0.7 liquid volumes per hour and per catalyst volume unit. The condensed mixture of products was separated into 76 parts of water and 422 parts of organic substances. After depositing 42 parts by distillation from 42 to 114 ° C under atmospheric pressure, the residue of the organic material was treated with water under a pressure of 70 kg / cm 2 in the presence of a Raney nickel hydration catalyst at 1 ° C until the water absorption ceased. After removal of the catalyst, the mixture was subjected to fractional distillation. The following fractions were collected: Distillation pressure (mm Tag, minimum, at maximum temperature) 1 83.0 2 164 89.0 3 94 98.0 1-2 4 98.2 1 2. bottom batch Fraction 2 was distilled with anga (for removal of unaffected tetrahydropyran-2-methanol). dried and redistilled. This gives 103 parts of cyclopentanemethanol, which des-.

Distillation temperature ('C, maximum) No.

Mangd (parts) - - added Over at 162.2 to 164.9 ° C (literature figure 162.5 to 163.5 ° C) and a further 31 parts, which distilled Over up to 167 ° C. Fraction 4 crystallized on storage. The crystals were identified as crystals of hexamethylene glycol. After washing with ether, the crystals melted at 39.5 to 40 ° C on their own as in a mixture with an authentic sample of hexamethylene glycol having a melting point of 39 to 40 ° C.

Example III.

A catalyst was prepared by impregnating activated alumina of the same kind as in Example I with an aqueous solution of chromic acid and drying the impregnated alumina. The catalyst contained 15% by weight of chromium.

A mixture of gaseous tetrahydropyran 2-methanol and hydrogen in the 2: 1 molar ratio was contacted with this catalyst in the heated reaction tube used in Example 1 at a catalyst temperature of 37 ° C and with a feed rate of 0.33 liquid volumes of tetrahydropyran. 2-methanol per hour and unit volume of the catalyst. The partially hydrogenated organic products from the dehydration were separated from the water formed in the reaction, and further hydrogenated in the presence of a Raney nickel hydrogenation catalyst at 125 ° C and an aqueous pressure of about kg / cm as a fraction which distilled Indian 73.4 ° C to 78 ° C at a pressure of 20 mm Hg, in an amount corresponding to 59% by weight of the mixture which was subjected to distillation.

Example IV

Dimethyltetrahydropyran-2-methanol, which is produced from methacrolein, was passed in a gas stream in contact with activated alumina of the same kind as in Example I in the reaction tube used in Example I at a temperature of 350 ° C and a feed rate corresponding to 0.67 liquid volumes per hour and unit of volume of the catalyst. The mixture, which leached the reaction tube, was collected. Of 227 parts of dimethyltetrahydropyran-2-methanol, 149 parts of crude products are obtained after removal of the water. Upon distillation of these crude products, 25 parts of dimethylcyclopentanecarboxaldehyde were obtained, which distilled off between 63.2 ° and 66.6 ° C at a pressure of 15 mm Hg and had a refractive index (n20 / D) of 1.4520. The climethylcyclopentanecarboxaldehyde thus prepared was found to contain 75.87 percent carbon, and 10.88 percent vate (calculated amounts for C81-114 0: 76.05 percent and 11.17 percent, respectively). It was found to have a carbonyl value of 0.715 equivalents per 100 g against a calculated value of 0.793 equivalents per 100 g.

Example V.

Tetrahydropyran-2-methanol was contacted with anhydrous calcium sulfate in the reaction tube used in Example 1 at a temperature of 4 ° C and a feed rate of 0.5 liquid volumes of tetrahydropyran-2-methanol per unit volume of catalyst. The products which left the reaction tube were collected and hydrogenated in the presence of a Raney nickel catalyst at 1 ° C and a water pressure of about 105 kg / cm 2 until the water absorption ceased. Distillation of the hydrogenated product gives a yield of cyclopentane methanol, corresponding to a conversion of 37%, based on the amount of tetrahydropyran-2-methanol supplied and a yield of 42%, based on the amount of tetrahydropyran-2-methanol consumed. 11 percent of the tetrahydropyran-2-methanol was recovered in unchanged form.

Example VI.

A catalyst consisting of basic aluminum phosphate, which had been prepared in the manner described in U.S. Pat. No. 2,365,623, was placed in the reaction tube used in Example I. Tetrahydropyran-2-methanol was passed in gaseous state into contact with the catalyst at a temperature of 325 ° C and a feed rate of 0.55 liquid volumes of tetrahydropyran-2-methanol per hour and unit volume of the catalyst. The resulting mixture was collected and hydrogenated in the same manner as in the previous example. Upon distillation of the hydrogenated products, cyclopentane methanol was recovered, corresponding to a conversion of 30 percent and a yield of 38 percent. In addition, hexamethylene glycol was obtained in an amount corresponding to a conversion of 10 percent. Unchanged tetrahydropyran-2-methanol was recovered in an amount corresponding to 20 percent of the amount supplied.

Example VII.

A catalyst was prepared by forming silica on activated aluminum of the same kind as in Example I with a grain size corresponding to 10 to 14 meshes from a water% suction of sodium silicate by adding acid. The catalyst contained 5 percent silicic acid (shaved as dry weight) and consisted of porous nuclei, which had a specific surface area of from 309 to 340 in per gram. Tetrahydropyran-2-methanol was contacted with the catalyst in the reaction tube of Example 1 at a catalyst temperature of 300 ° C and at a feed rate of 0.59 liquid volumes of tetrahydropyran-2-methanol per hour and unit volume of the catalyst. The resulting mixture of products was hydrogenated according to the method used in Example V and distilled. Cyclopentane methanol was recovered in an amount corresponding to a conversion of 42 percent, shaved off the added amount of tetrahydropyran-2, methanol. If the amount of tetrahydropyran-2-methanol added was recovered, 42 percent was recovered in unchanged form. .6'1272 (0 -

Claims (9)

Patent claim: A process for producing cyclopentanecarboxaldehydes or derivatives claray, consisting in subjecting a tetrahydropyran-2-methanol to the action of a dehydration catalyst at an elevated temperature, typically between 250 and 500 ° C, and optionally converting the resulting cyclopentanecarboxaldehyde to derivatives. A kit according to claim 1, in which tetrahydropyran-2-methanol or in carboxyl alkyl or aryl-substituted products was used. Set according to claim 1 or 2, in which a temperature between about 300 and about 450 ° C is used. 4. sat according to claims 1-3, in which the catalyst contains one or Hera metal oxides. 5. sat according to claim 4, in which the catalyst contains activated alumina. The set of claims 1-3, wherein the catalyst contains one or more salts of polyvalent metals, typically phosphates or sulfates. 7. A kit according to any one of claims 1-6, in which the cyclopentanecarboxaldehydes produced are converted by hydrogenation into the corresponding cyclopentane methanol. A kit according to any one of claims 1-7, wherein the treatment of the tetrahydropyran-2-methanol. is carried out in the presence of hydrogen and the catalyst consists of a dehydration hydrogenation catalyst, whereby the cyldopentanecarhoxaldehyde, at the same time as its formation, is completely or partially converted to the corresponding cyldopentanmethanol. A kit according to claim 8, wherein the catalyst contains alumina and chromium oxide. Stockholm 1950. Irungl. Bolitr. P. A. Norstedt & Saner 500089