An improved and efficient process for the scalable preparation of optically pure trans-2-aminocyclohexanols

摘要

An improved and efficient process has been developed for a green and scalable preparation of optically pure (1R,2R)- and (1S,2S)-trans-2-aminocyclohexanols. The process utilised hot water to promote the aminolysis of cyclohexene oxide by benzylamine to afford racemic trans-2-(benzylamino)cyclohexanols, which were resolved by sequential and repeated use of (R)- and (S)-mandelic acid. Finally, after treatment of the two salts sequentially with HCl and NaOH and recovery of mandelic acid, liberation was achieved of the optically pure trans-2-benzylaminoaminocyclohexanols which were smoothly debenzylated using a low loading of a Pd/C catalyst to the trans-2-aminocyclohexanols. The synthetic route has been successfully applied to large-scale (1 mol) preparations in good yield.