Aza-pinacol rearrangement: acid-catalyzed rearrangement of aziridines to imines

A series of di-, tri-, and tetra-substituted N-tosylaziridines [N-(toluene-p-sulfonyl) aziridines] 1, prepared by aziridination of the corresponding alkenes with N-[(tolyl-p-sulfonyl) imino] phenyliodinane (TsN = IPh), was found to undergo a BF3-catalyzed rearrangement (aza-pinacol rearrangement) under mild conditions to give the corresponding N- tosylimines 2 generally in satisfactory yields.