STEREOCHEMICAL OBSERVATIONS IN THE SYNTHESIS OF NOVEL RAHYDRO-5-PHENYL-2H-AZETO[2,1-A]ISO-QUINOLIN-2-ONE DERIVATIVES

Imine (5) reacted with Cl2CHC(O)Cl in die presence of Et3N to give bet a-lactams (7a) and (7b) in a 4:1 ratio. The stereochemistry of cycload duct (7a) was confirmed by X-ray analysis. Uncyclized intermediates we re identified. Reduction of dichloro beta-lactam (7a) with Zn/HOAc gav e mostly exo monochloride (13a), with high stereoselectivity (10:1 rat io). Reduction of a mixture of exo and endo monochlorides (13a) and (1 3b) with Zn/HOAc indicated that the more sterically hindered endo chlo rine is preferentially attacked. Reduction of (7a) with Bu3SnH gave be ta-lactam (14a) as the major product.