B 2 (OH) 4 -Mediated Reductive Ring-Opening of N -Tosyl Aziridines by Nitroarenes: A Green and Regioselective Access to Vicinal Diamines.

The nucleophilic ring-opening of aziridine derivatives provides an important synthetic tool for the preparation of various β-functionalized amines. Amines as nucleophiles are employed to prepare synthetically useful 1,2-diamines in the presence of various catalysts or activators. Herein, the B 2 (OH) 4 -mediated reductive ring-opening transformation of N -tosyl aziridines by nitroarenes was developed. This aqueous protocol employed nitroarenes as cheap and readily available amino sources and proceeds under external catalyst-free conditions. Control experiments and DFT calculations pointed to the in situ reduction of nitroarenes to aryl amines via N -aryl boramidic acid ( E ) and an S N 1-type ring-opening of N -tosylaziridines by the resultant aryl amines with high regioselectivity.