Substituent effects in the Fischer indolization of (2- sulfonyloxyphenyl)hydrazones (Fischer indolization and related compounds. XXX)

Article abstract of DOI:10.1248/cpb.47.791

The effects of a variety of additional of ethyl pyruvate 2-(2- methanesulfonyloxy)phenylhydrazone (7) in Fischer indolization were examined. When the substituent was a methyl group at the 3-, 4-, or 5-position, the yields of normal 7-methanesulfonyloxyindoles depended upon the position. The hydrazones having a methyl group at the position nearer to the methanesulfonyloxy group tended to give normal 7-methanesulfonyloxyindole in a higher percentage to total indolic products. In a series of 4-substituted phenylhydrazones (7d, e, f), more electron-withdrawing substituents tended to give normal 7-methanesulfonyloxyindole in a higher percentage to total indolic products than electron-donating ones. A hydrazone with a strong electron-withdrawing substituent at the 4-position (7f) underwent intramolecular aromatic nucleophilic substitution by the enehydrazine moiety to give the cinnoline derivative.

Full text of DOI:10.1248/cpb.47.791

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