Stereoselective hydrogenation of terpenes using platinum-based catalysts

In the present paper, the catalytic hydrogenation of some terpenes is discussed. Catalysts employed were silica supported Pt and Pt modified by tin addition using techniques derived from surface organometallic chemistry on metals. Selected substrates were a-pinene, verbanone, fenchone, camphor and verbenone. The catalytic systems studied allow the control of reaction stereoselectivity. The hydrogenation of (X-pinene led selectively to cis-pinane, and it was possible to observe that the modification Of Pt/SiO2 with Sn caused an important decrease of the catalytic activity; this fact can be explained by combined electronic and geometrical effects. In sterically hindered terpenones (fenchone and camphor), the topography of the molecule resulted of fundamental importance in controlling the stereoselectivity of the reaction. In verbenone hydrogenation, the Pt/SiO2 catalyst allowed to obtain cis-verbanone with high yield and catalysts modified with Sn led to the formation of a principal product (cis-verbanol) different than the one obtained by chemical reduction with NaBH4 (cis-verbenol). (c) 2006 Elsevier B.V. All rights reserved.