Application of enolates of activated carboxylic acid derivatives in organic synthesis - Novel syntheses of beta-lactones

Ester enolates derived from alkyl esters of alkanoic acids react with carbonyl compounds in an aldol type reaction forming alkyl beta-hydroxyalkanoates. The substitution of an alkyl ester by the corresponding phenyl ester causes the formation of beta-lactones via a spontaneous intramolecular cyclization of the intermediately formed O-metalated phenyl beta-hydroxyalkanoates. This reaction is not restricted to enolates of activated esters. Enolates of other activated derivatives of carboxylic acids, such as benzotriazolides, are also useful starting materials for these versatile one-step beta-lactone syntheses.