STEREOSELECTIVE THYMOL HYDROGENATION - COMPARATIVE-STUDY OF CHARCOAL-SUPPORTED, PLATINUM, RHODIUM AND IRIDIUM CATALYSTS

The catalytic properties of Pt, Rh and Ir catalysts in the reduction of thymol have been compared, with respect to their activities and stereoselectivities in the formation of menthones and menthols. The reduction over Pt and Rh proceeds essentially via the ketone intermediates, whereas the direct route is predominant on Ir. The formation of the cis isomers is always highly favored. The stereoselectivity of thymol reduction is controlled by the relative proportions of these two routes and by their stereoselectivities.