One-pot synthesis of Weinreb amides employing 3,3-dichloro-1,2-diphenylcyclopropene (CPI-Cl) as a chlorinating agent

The synthesis of Nα-protected amino alkyl Weinreb amides starting from the corresponding α-amino acids as well as carboxylic acids has been delineated through the in situ generation of acid chlorides using CPI-Cl as a chlorinating agent. The protocol is simple; the reaction conditions employed were mild, and compatible with all the three commonly used urethane protecting groups namely, Boc, Cbz and Fmoc groups. The resulting Weinreb amides are obtained in good yields as optically pure products.