Formation d'enolates cetoniques par action d'organomagnesiens mixtes dans l'hexamethylphosphorotriamide sur des esters. : Direction des enolisations,limites, utilisation a la preparation de cetones

Alkylmagnesium halides in HMPA react with aliphatic esters to form predominantly the less substituted ketonic enolates. The direction of these enolizations is more selective than that of intermediate ketones. Aliphatic esters are only slightly or not at all enolized under these conditions. Hydrolysis, deuterolysis and alkylation of the ketonic enolates give the corresponding ketones. Benzoic acid derivatives and α-β unsaturated aliphatic and aromatic esters give only low yields of ketonic enolates. The low enolization of the intermediate ketones by these alkylmagnesium halides can explain this result.