Fischer Indolization and Its Related Compounds. XVIII. Formation of Four Unexpected Angular Benz [e] indoles on Fischer Indolization of Ethyl Phenylpyruvate 2-[(1, 4-Dimethoxy-2-naphthyl) hydrazone]

Abstract

The Fischer indolization of ethyl phenylpyruvate 2-[(1, 4-dimethoxy-2-naphthyl) hydrazone] (2) with ethanolic hydrogen chloride gave four angular benz [e] indole products (ethyl 4-chloro-5-ethoxy-(14a), ethyl 4-chloro-5-methoxy-(14b), ethyl 5-ethoxy-(14c), and ethyl 5-methoxy-(14d)-1-phenyl-3H-benz [e] indole-2-carboxylates), instead of the anticipated linear benz [f] indole, ethyl 4, 9-dimethoxy-3-phenyl-1H-benz [f] indole-2-carboxylate (3). Oxidation of these benz [e] indole derivatives (14b and 14d) with chromic acid in acetic acid provided an o-quinone derivative (15) which showed anti-viral activity in a preliminary biological test.