New synthesis of 3-arylpyrrolines

We present an easy and straightforward synthesis of 3-arylpyrrolines 4a-g by repeated treatment of 4-aryl-1,2,5,6-tetrahydropyridines 2a-g with m-chloroperoxybenzoic acid (MCPBA) and boron trifluoride etherate (BF3-OEt2). The transformation proceeds via epoxidation, ring contraction, Baeyer-Villiger oxidation and elimination reaction and affords 3-arylpyrrolines 4a-g with 61-70% yield. This facile strategy was also used to synthesize racemic baclofen (6).