Reactions of 4,5-dihydro-5-methylpyrano[4,3-b]indole-1,3-dione; a synthesis of N-methylisotryptophol

Abstract

Boiling 4,5-dihydro-5-methylpyrano[4,3-b]indole-1,3-dione (7) with alcohols followed by decarboxylation of the half-esters so formed leads to esters of 1-methylindol-2-ylacetic acid; reduction of these esters then affords N-methylisotryptophol [2-(1-methylindol-2-yl)ethanol](10). Reaction of 3-carboxy-1-methylindol-2-ylacetic acid (6; R = H) with acetic acid-sodium acetate gives 3,5-dimethylpyrano[4,3-b]indol-1(5H)-one (17); with dimethylformamide–phosphorus oxychloride, 4-(NN-dimethylaminomethylene)-4,5-dihydro-5-methylpyrano[4,3-b]indole-1,3-dione (22) was obtained.