Imine (5),4-phenyl-3,4-dihydroisoquinoline, reacted with Cl 2 CHC(O)Cl in the presence of Et 3 N to give β-lactams, azeto[2,1-a]isoquinolin-2-one derivatives, (7a) and (7b) in a 4:1 ratio. The stereochemistry of cycloadduct (7a) was confirmed by X-ray analysis. Uncyclized intermediates were identified. Reduction of dichloro β-lactam (7a) with Zn/HOAc gave mostly exo monochloride (13a), with high stereoselectivity (10:1) ratio. Reduction of a mixture of exo and endo monochlorides (13a) and (13b) with Zn/HOAc indicated that the more sterically hindered endo chlorine is preferentially attacked. Reduction of (7a) with Bu 3 SnH gave β-lactam (14a) as the major product