Cu 2 (OTf) 2 ‐Catalyzed and Microwave‐Controlled Preparation of Tetrazoles from Nitriles and Organic Azides under Mild, Safe Conditions

Avoiding hazards: Cu2(OTf)2⋅C6H6 (OTf=O3SCF3) is the catalyst of choice for the [3+2] cycloaddition of organic azides and ethyl cyanoformate or related nitriles (see scheme; PG=protecting group, EWG=electron-withdrawing group). For the first time, tetrazoles are obtained from these substrates at room temperature; heating at 80 °C in CH2Cl2 (microwave reactor) is only required for the most reluctant substrates.