An improved procedure for the preparation of 1‐benzyl‐1H‐1,2,3‐triazoles from benzyl azides

A procedure for the preparation of substituted 1‐benzyl‐1H‐1,2,3‐triazoles from benzyl azides under very mild conditions is described. The method provides improved yields and extends the scope of the Dimroth Reaction to other types of active methylene compound to those previously used. Benzyl azides react with active methylene compounds in dimethyl sulphoxide catalysed by potassium carbonate at 35–40° to give 1H‐1,2,3‐triazoles usually in good yield. Acetonitrile derivatives gave 5‐amino‐1H‐1,2,3‐triazoles whereas diethyl malonate gave 5‐hydroxy‐1H‐1,2,3‐triazoles. 1H‐1,2,3‐Triazole‐4‐carboxylate esters and 1H‐1,2,3‐triazole‐4‐ketones were obtained from ethyl acetoacetate and β‐diketones respectively. Benzyl methyl ketone reacted to give a 5‐methyl‐4‐phenyl‐1H‐1,2,3‐triazole, but acetone and acetophenone failed to react. Other active methylene compounds which did not react under these reaction conditions included ethyl cyanoacetate, ethyl fluoroacetate and ethyl nitroacetate.