Studies on the syntheses of heterocyclic compounds. Part DXIV. Synthesis of 6a,7-didehydroaporphine and indolo[2,1-a]isoquinoline systems by benzyne reactions

Abstract

The benzyne reaction of 1-(2-bromo-4,5-dimethoxybenzyl)-3,4-dihydro-7-hydroxy-6-methoxyisoquinoline (3) methiodide with sodium methylsulphinylmethanide in dimethyl sulphoxide afforded 6a,7-didehydro-2,9,10-trimethoxyaporphin-1-ol (7), which on reduction gave (±)-thaliporphine (2). 5,6-Dihydro-2,3,9,10-tetramethoxyindolo[2,1-a]isoquinoline (6) and its 2-hydroxy-analogue (5) were also obtained through benzyne reactions of 1-(2-bromobenzyl)-3,4-dihydroisoquinolines under similar conditions.