Oxidation of 2-ethylthioindoles with hydrogen peroxide. Oxidative migration of the ethylsulphonyl group

Abstract

Oxidation of 2-ethylthioindoles (1) with three molar equivalents of hydrogen peroxide in acetic acid yielded the sulphones (6a, b, and d), the 3-ethylsulphonylindolin-2-ones (7a, b, and d), and the 3-hydroxyindolin-2-ones (8b and d); the sulphoxides (5a, b, d, and e) were the main products with one molar equivalent of hydrogen peroxide. Compounds (7) and (8) were also obtained by oxidation of 2-ethylsulphonylindoles (6) with one molar equivalent of hydrogen peroxide in acetic acid, indicating that oxidative migration of the ethylsulphonyl group was occurring.