Synthesis of 7,12-dihydro-12-phenyl-5H-6,12-methanodibenz[c,f]azocines via N,N-dibenzylphenacylamines

Abstract

N,N-Dibenzylphenacylamines (1) were prepared in high yields by a one-pot reaction and cyclized at room temperature to give 7,12-dihydro-l2-phenyl-5H-6,1 2-methanodibenz[c,f]azocines in high yields. 95% H2SO4 or 70% HClO4 was used as cycIization catalysts. The double-cyclization proceeds smoothly in the cases where electron-donating groups are present in both benzene ring. N-2,3-dimethoxybenzyl-N-benzylphenacylamine (1f) gave the corresponding N-benzyl-1,2-dihydro-4-phenylisoquinoline on treatment with 95% H2SO4 while N-3,4-Dimethoxybenzyl-N-benzylphenacylamine (1a) at the same reaction conditions and reaction time cyclized to the corresponding dibenzazocine. However 1a gave the corresponding dihydroisoquinoline which disproportionates to give N-benzyl-1,2,3,4-tetrahydro-4-phenylisoquinoline and N-benzyl-4-phenylisoquinolinium when treated with 70% perchloric acid al room temperature.