Abstract One-carbon homologated N-(α-haloacyl) benzotriazoles have been synthesized from the corresponding aromatic and aliphatic aldehydes. Vinylbenzotriazoles, prepared by the reaction of aldehydes with the one-carbon synthon BtCH 2 P+ Ph 3 Cl-, were subsequently treated with Br 2/Et 3 N to give 1-bromovinylbenzotriazoles. These were then treated with NBS/NIS in CH 3 CN-H 2 O to furnish one-carbon homologated N-(α-haloacyl ...