Fischer Indolization and Its Related Compounds. VI. Effect of Reagents and Substituent of the ortho-Substituted Phenylhydrazone on Abnormal Fischer Indolization

Treatment of ethyl pyruvate 2-methoxyphenylhydrazone (1) with Lewis acid gave 5-substituted and/or 5-methoxy-indole products with ethyl 7-methoxyindole-2-carboxylate (2) as a main product. It contrasts strikingly with the results reported in the previous paper1) on a reaction center of the abnormal Fischer indolization. It was also found that differences of the acid strength of the reagent and of the electron density on a benzene ring due to introduction of some other additional substituents could be the determinant for the direction of the adnormal transformation.