Effective amidation of carboxylic acids using (4,5-dichloro-6-oxo-6H- pyridazin-1-yl)phosphoric acid diethyl ester

Abstract

(4,5-Dichloro-6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl ester (3a) are efficient and selective coupling agents for the amidation of carboxylic acids. Amidation of aliphatic and aromatic carboxylic acids with aliphatic and aromatic amines using 3a under mild condition gave chemoselectively the corresponding amides in good to excellent yield. Three protected-dipeptides were also synthesized from N-BOC-Phe and O-Meamino acid hydrochlorides using 3a under mild condition.