NONOXIDATIVE 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 BETA-HYDROXY ESTER VIA THE AZOLIUM SALT

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 beta-lactone on treatment with base but did undergo clean de-acylation in the presence of methanol and base to give the corresponding beta-hydroxy ester stereospecifically.