Transition Metal-Catalyzed Radical Cyclizations: A Low-Temperature Process for the Cyclization of N-Protected N-Allyltrichloroacetamides to Trichlorinated γ-Lactams and Application to the Stereoselective Preparation of β,γ-Disubstituted γ-Lactams

Cyclizations of N-substituted N-allyltrichloroacetamides, where the substituent is an alkyl, Cbz, Boc, Ts, or Ms group, are catalyzed by a 1:1 mixture of CuCl and bipyridine to give the corresponding β,γ-trichlorinated γ-lactams in high yields. The reactions proceed at temperatures from −78 °C to room temperature. Cyclizations of N-allyltrichloroacetamides of acyclic secondary allylic amines are achieved with good selectivity; the cis/trans ratios of the γ-lactams formed were dependent on the substituents on the nitrogen atom. The stereochemical outcome is compared with that of free-radical cyclization.