New Synthetic Reactions Based on the Onium Salts of Aza‐Arenes [New synthetic methods (29)]

Abstract

Abstract Effective syntheses employing 2‐halogenated pyridinium, benzoxazolium, benzothiazolium, and pyridinium salts have been accomplished in the absence of strong acids and bases. Activation of carboxylic acids or alcohols with these onium salts leads to 2‐acyloxy and 2‐alkoxy intermediates which can be transformed into esters, amides, thiol esters, (macrocyclic) lactones, acid fluorides, olefins, allenes, carbodiimides isocyanates, isothiocyanates, nitriles, and isocyanates. The possibility of performing stereospecific syntheses (involving configurational inversion) with onium salts deserves attention.