Diastereoselective 5-exo-trig radical cyclisation on N-acryloyl-tetrahydro-1,3-oxazines. A novel approach to enantiopure 3-substituted pyrrolidines

Article abstract of DOI:10.1016/S0040-4039(96)02091-6

N-acryloyl-2-(phenylselenomethyl)-tetrahydro-1,3-oxazine 1 generates a carbon-centred radical in the presence of tri-n-butyltin hydride and AIBN. This radical underwent diastereoselective 5-exo-trig cyclisation leading to a mixture of five-membered lactams 2a and 2b (d.e. 68%). Chromatographic separation of the diastereomers and elimination of the chiral auxiliary provided enantiopure (R)-3-methylpyrrolidine in good chemical yield. Copyright (C) 1996 Elsevier Science Ltd.