Oxidation of 2,3-disubstituted indoles with m-chloroperbenzoic acid. Formation of o-aminophenol derivatives and a dimeric product

Abstract

Oxidation of tetrahydrocarbazole (5) with m-chloroperbenzoic acid in methylene dichloride at –60 °C gave the N-benzoyl-o-aminophenol (11) together with the hydroxy-3H-indole (7) and the indol-3(2H)-one (9). The N-benzoyl-o-aminophenol (11) was found to be derived from the hydroxy-4aH-carbazole (7)via an unstable tertiary amine intermediate (17) by further oxidation. The N-benzoyl-o-aminophenol (11) was also obtained by the oxidation of the other hydroxy-3H-indoles (18), (19), and (24). On the other hand, similar oxidation of N-methyl-tetrahydrocarbazole (6) gave the hydroxyenamine (28) and its dimer (27), and of 2,3-diphenylindole (31) and the N-methyl derivative (30) gave the hydroxy-3H-indole (19) and the ketoamide (33), while the 1,4-benzoxazine derivatives (34) and (35) were obtained in the case of the N-acetyl derivative (32).