Non-oxidative conversion of ketone carbonyls into carboxy carbonyls. Comparison of 2-acylthiazoles and 2-acylimidazoles in the aldol condensation and the stereospecific cleavage of an example of the latter to a β-hydroxy ester via the azolium salt

Abstract

The synthesis of some 2-acyl-thiazoles and -imidazoles is described. In the subsequent aldol condensation of these ketones, the imidazole congeners were much better behaved. N-Methylation of the imidazole aldols was only partially successful and suffered from competing O-methylation of the hydroxy group. A diastereoisomeric imidazolium salt from one of the aldols did not close to a β-lactone on treatment with base but did undergo clean de-acylation in the presence of methanol and base to give the corresponding β-hydroxy ester stereospecifically.