Stereoselective one-pot synthesis of β-lactams by reaction of 2-pyridylthioesters with imines in the presence of AlBr3 or EtAlCl2

The reactions of some 2-pyridylthioesters with imines in the presence of AlBr3 or EtAlCl2 and of a tertiary amine afford β-lactams in a simple one-pot procedure with fair to high trans stereoselectivity. The condensation can be also carried out in the absence of base and with sub-stoicheiometric amounts of the Lewis acid. The possible mechanisms of the process are discussed.