Resolution of racemic trans-1,2-cyclohexanediol with tartaric acid

Abstract

A simple method for the resolution of racemic trans-1,2-cyclohexanediol enantiomers is presented in this paper. The chiral discrimination was performed by tartaric acid via diastereomeric complex formation. The diastereomeric complexes were formed by adding the resolving agent to the racemic diol in a 0.5:1 molar ratio. The (2 R,3 R)-(+)-tartaric acid forms stable diastereomeric complex with (1 R,2 R)-(−)-cyclohexanediol. Supercritical carbon dioxide extraction was applied to the separation of the mixture of diastereomeric complexes and uncomplexed diol enantiomers. We found unexpected optimal conditions according to the 3 2 factorial design on the resolution efficiency within the studied range of the extraction pressure and temperature. In the best cases, the (1 S,2 S)- and (1 R,2 R)-diol enantiomers were obtained with ee (1 S,2 S) = 62% and ee (1 R,2 R) = 93% enantiomeric excess in one equilibrium stage, respectively.