Studies on the Syntheses of Heterocyclic Compounds. DCCLIV. A Novel Method form Acetalisation of Formyl Group at the C₃-Position of 2, 3-Dihydro-1H-pyrrolo [1, 2-a] indole Skeleton

Abstract

Reaction of 2, 3-dihydro-7-methoxy-6-methyl-1H-pyrrolo [1, 2-a] indole-9-carboxaldehydes (2), (3), (4), (5), and (6) with thiolacetic acid in the presence of 6 N sulphuric acid at room temperature gave 9-diacetylthiomethyl-2, 3-dihydro-7-methoxy-6-methyl-1H-pyrrolo [1, 2-a] indoles (12), (13), (14), (15), and (16), respectively. The same reaction of the compound (2) at 0° afforded 1-acetoxy-9-diacetylthiomethyl-2, 3-dihydro-7-methoxy-6-methyl-8-nitro-1H-pyrrolo [1, 2-a] indole (11). Successive treatment of the compound (11) with absolute methanol in the presence of sodium methoxide gave 2, 3-dihydro-1-hydroxy-7-methoxy-9-dimethoxymethyl-6-methyl-8-nitro-1H-pyrrolo [1, 2-a] indole (17).