Rhodium-catalyzed Reformatsky-type reaction for asymmetric synthesis of difluoro-β-lactams using menthyl group as a chiral auxiliary

We developed a new methodology for the asymmetric Reformatsky-type reaction of (−)-menthyl bromodifluoroacetate (2) with imine in the presence of RhCl(PPh3)3. Ester 2 with the cost-effective chiral auxiliary gave (S)-difluoro-β-lactams in moderate to good yields and high diastereoselectivities through spontaneous removal of the auxiliary.