Reactions of carbonyl compounds in basic solutions. Part 11. The Baker-Venkataraman rearrangement

Abstract

The detailed mechanism of the Baker–Venkataraman rearrangement has been studied. The kinetics of the rearrangement of a series of 2-acetylphenyl 3- or 4-substituted benzoates and acetylnaphthyl benzoates catalysed by a basic ‘non-nucleophilic’ buffer in dimethyl sulphoxide have been measured. Studies of substituent effects, kinetic isotope effects, and acidity function correlations indicate a pathway involving pre-equilibrium formation of the carbanion, followed by rate-determining intramolecular nucleophilic attack. The methanolysis of the 2-acetylphenyl benzoates catalysed by methoxide in methanolic dimethyl sulphoxide has been similarly investigated. In this case the pathway appears to involve neighbouring group participation by the ketonic carbonyl group.