The Chemistry of Carbanions. X. The Selective Alkylation of Unsymmetrical Ketones

Abstract

Solutions of enolate anions which retain their structural and stereochemical integrity can be prepared by reaction of the corresponding enol acetates with 2 equiv. of methyllithium in 1,2-dimethoxyethane. By use of this procedure it is possible to effect the selective alkylation of unsymmetrical ketones at either the more or less highly substituted a-position, utilizing the appropriate enol acetate derivative of the ketone. Selective alkylations of 2-heptanone, 2-methylcyclopentanone, 2-methylcyclohexanone, and 1-decalone are described. The proportion of cis-fused 9-methyl-1-decalone obtained from alkylation of 1-decalone can be significantly enhanced by use of the very reactive alkylating agent, trimethyloxonium 2,4,6-trinitrobenzenesulfonate. © 1965, American Chemical Society. All rights reserved.