Selective Demethylation of 1-Substituted-6, 7-dimethoxy-3, 4-dihydroisoquinoline Derivatives and Modified Total Synthesis of (±)-Salsoline : Studies on the Syntheses of Heterocyclic Compounds. CLXV.

Abstract

Boiling of 1-substituted 6, 7-dimethoxy-3, 4-dihydroisoquinoline derivatives (X and XII) in constant-boiling point hydrochloric acid at ordinary pressure, in nitrogen stream, for 50 hours resulted chiefly in selective demethylation of the methoxyl at 7-position to form the compounds XI and XIII, respectively. On the other hand, treatment of X and XII with metallic sodium or with metallic lithium and liquid ammonia resulted in selective demethylation of the methoxyl in 6-position, with concurrent reduction of the C=N bond to form dl-salsoline (XVI) and the compound (XVIII).