Stereoselective hydrogenation of cyclic unsaturated cpds. - with modified Raney nickel catalyst esp. of (trans)-piperitol

摘要

Cyclic unsatd. cpds. having OH on an asymmetric centre of the ring and with an olefinic C=C bond are catalytically hydrogenated so that this bond creates an additional asymmetric centre in the ring. Increased stereoselectivity is achieved by increasing addn. of the H to the side of the olefinic bond on the same side of the molecule as the OH. The catalyst is a Ni catalyst with an effective fraction of its surface inactivated with an inorganic salt of a metal of Gps. (I)-(VIII), Periods 4-7 of the Periodic Table, of the Rare Earths or of Al; organic halides; hydrogen halides; or halides of B or As. In an example, d-isomenthol was largely obtd. when d-trans-piperitol was hydrogenated with Raney Ni pre-treated with NiCl2.