Complementary stereoselective cyclisations of N-(3,4-dimethoxybenzyl)ephedrine and its chromium tricarbonyl complex to trans- and cis-2,3-dimethyl-4-phenyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines respectively
Abstract
Acid promoted cyclisations of N-(3,4-dimethoxybenzyl)ephedrine and its chromium tricarbonyl complex occur with completely complementary stereoselectivities to give exclusively trans-(–)- and cis-(+)-2,3-dimethyl-4-phenyl-6,7-dimethoxytetrahydroisoquinolines respectively.