The chemistry of amine-azide interconversion: Catalytic diazotransfer and regioselective azide reduction

Azides have proven to be useful precursors to amines in organic syntheses. This report describes an improvement of the diazotransfer reaction and the first example of a regioselective azide reduction of compounds containing multiple azides. The use of a specific ratio of solvents and zinc chloride as a catalyst resulted in a more efficient diazotransfer reaction capable of delivering >90% conversion per amine with shorter reaction times than those previously reported. Azides can be reduced with good regioselectivity in moderate yields by a modification of the Staudinger reaction using trimethylphosphine at low temperatures, Electronic factors determine the selectivity for azide reduction, and the reaction is predictable by NMR analysis of the starting material. Several examples for the diazotransfer and regioselective azide reduction reactions are given, and a mechanistic hypothesis for both is proposed.