Cyclohexanecarboxylic acid reduction

Sodium in liquid ammonia and ethanol reduced benzoic acid to 1,4-dihy-drobenzoic acid. Reduction of p-toluic acid was more complicated and afforded a mixture of cis- and rranj-l,2,3,4-tetrahydro-p-toluic acid and cis-and tra j-l,4-dihydrotoluic acid. m-Methoxybenzoic acid yielded 1,2,3,4-tetrahydro-5-methoxybenzoic acid, and 3,4,5-trimethoxybenzoic acid gave l,4-dihydro-3,5-dimethoxybenzoic acid in 87% yield (after hydrogenolysis of the methoxy group para to carboxyl) [984. In the case of 4 -methoxy-biphenyl-4-carboxylic acid, sodium in isoamyl alcohol at 130° reduced completely only the ring with the carboxylic group, thus giving 92% yield of 4-(p-methoxyphenyl)cyclohexanecarboxylic acid [955]. 

Reactions. w-Hydroxybenzoic acid affords a variety of products, depending on the catalyst and conditions employed. Catalytic reduction over platinum black or platinum oxide in alkaline solution gives 3-hydroxycyclohexanecarboxylic acid [22267-35-2]. Reduction of a warm aqueous solution over platinum oxide or over colloidal platinum yields cyclohexanecarboxylic acid. w-Hydroxybenzaldehyde can be prepared by reducing ///-hydroxybenzoic acid with sodium amalgam. Finally, reduction over Raney nickel gives cydohexanol. 

The first McCasland s pseudo-sugar, pseudo-a-DL-talopyranose (P) was synthesized from 4-acetoxy-2,3-dihydroxy-5-oxo-cyclohexanecarboxylic acid (6) as follows [13]. Reduction of the oxo acid 6 with sodium borohydride and subsequent esterification with methanol and trifluoroacetic acid, followed by acetylation gave methyl (1, 2, 3, 4/5)-2, 3, 4, 5-tetraacetoxycyclohexanecarboxylate (7). Hydrogenation of 7 with lithium aluminium hydride and successive acetylation yielded pseudo-a-DL-talopyranose pentaacetate (8). Hydrolysis of 8 in ethanolic hydrochloric acid gave pseudo-a-DL-talopyranose 9 in 23% overall yield from 6 [1] (Scheme 6). 

Hexahydronicotinic acid (90%) is obtained by catalytic hydrogenation of nicotinic acid at 3 atm. pressure over colloidal platinum. Preparation of the catalyst is described. The 9,10 double bond in the acridine nucleus is reduced at 10° by sodium amalgam in dilute sodium carbonate solution to give 9,10-dihydroacridine-S>-carboxylic acid in 70% yield. 2-Phenyl-cyclohexanecarboxylic acid (96%) is prepared by the selective reduction, of 2-phenylbenzoic acid by a large excess of sodium in refluxing amyl alcohol. ... 

Palladium hydrogenates arenes at elevated T (>90 C) and P (>20 X 10 kPa), but still finds industrial applications such as the preparation of cyclohexanecarboxylic acid, a caprolactam intermediate, by hydrogenation of benzoic acid in quantitative yield . Water increases the reduction rate over Pd catalysts, and strained rings can be hydrogenated over palladium-on-carbon in alcohol at Rt and P [equation (a)] . Compound 1 is readily hydrogenated the less strained compound 2 is inert. 

It was shown that the chromophores of myco(ansa)trienins I (95) and II (96) originated from a m-CyN unit and the ansa-chain from polyketide units (A-A-A-A-A-P-P-A). The cyclohexanecarboxylic acid moiety was derived from the sequential reduction of 2,5-dihydrobenzoic acid to... 

The biosynthetic origin of the cyclohexanecarboxylic acid moiety of the mycotrienins I (95) and II (96) was also considered to be shikimic acid (119) [184,204]. Cell-free extracts of Streptomyces collinus were tested with various cyclohexene- and cyclohexadiene-carboxylic acids in order to determine the latter stages of the conversion of 119 to cyclohexanecarboxylic acid. It was demonstrated that the final three steps of this process involve reduction of the a,P-double bond of 1,2(6)-cyclohexadienylcarbonyl CoA, an isomerization of the double bond of the resulting 2-cyclohexenylcarbonyl CoA to afford 1-cyclohexenylcarbonyl CoA, and a subsequent reduction of the newly formed a,P-double bond. Both of the reduction steps were shown to require NADPH as a cofactor [212]. 

The cyclohexane ring in phenyl cyclo-hexanecarboxylates and in the PCH compounds, 2.5, usually enhances nematic character relative to that of the aromatic systems and even greater enhancement is achieved with cyclohexyl cyclohexanecarboxylates or a bicyclohexyl core unit such as 2.6. The esters are prepared as outlined in Scheme 6 and the bicyclohexyl systems are obtained by the route shown in Scheme 2 a similar reduction of the aromatic ring to that shown in Scheme 6 and equilibration with thionyl chloride to give the trans-acid [28, 29] allows the terminal cyano compound to be obtained. 

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