4-(2-Oxopyrrolidin-1-yl)benzoic acid → Trans-4-(2-oxo-pyrrolidin-1-yl)cyclohexanecarboxylic acid

Participants

Reaction Steps

4-(2-Pyrrolidon-1-yl)benzoic acid (4.0 g, 0.0195 mol), 5% rhodium-carbon catalyst (2.8 g, 3.0% mol) and methanol (80 mL) are charged in an autoclave (300 mL) and stirred at room temperature for 5 hours under hydrogen pressure (50 atm, conversion rate >99%, cis:trans=50:50). The reaction solution is cooled, filtrated to collect the catalysts, and washed with methanol. The filtrate is concentrated under reduced pressure, and the resulting crystals are washed with methanol to give 4-(2-pyrrolidon-1-yl)cyclohexylcarboxylic acid as a mixture of cis and trans isomers (3.4 g, 82.5%, cis:trans=79:21). A portion (3.0 g) is dissolved in methanol (15 mL) under heating, and cooled. The resulting crystals are washed with cooled methanol to give cis-4-(2-pyrrolidon-1-yl)cyclohexylcarboxylic acid (700 mg, >99% de). The tertiary structure of cis-4-(2-pyrrolidon-1-yl)cyclohexylcarboxylic acid was confirmed by X-ray structure analysis. Mp: 188° C.

Provenance & Evidence