Method for producing optically active, racemic menthol

摘要

The present invention relates to a particularly economic overall method for producing menthol, specifically for producing optically active, essentially enantiomerically and diastereomerically pure L-menthol and racemic menthol, starting from the starting material citral which is available inexpensively on an industrial scale. The method has the following stepsa.1) catalytic hydrogenation of neral and/or geranial to give citronellal,b.1) cyclization of citronellal to isopulegol in the presence of an acidic catalyst,c.1) purification of isopulegol by crystallization andd.1) catalytic hydrogenation of isopulegol to give menthol.