Cu 0 ‐Promoted Cyclisation of Unsaturated α‐Halogeno Amides To Give β‐ and γ‐Lactams

Efficient 5‐ exo ‐ trig atom‐transfer radical cyclisation of 13 unsaturated α‐halogeno amides mediated by Cu 0 (copper wire) with tripyridylmethanimine ligand (TPMA; 1 mol‐%) in a mixed solvent of EtOAc/EtOH (3:1) is reported (89–98 %), with recycling of the copper wire. A substantial improvement in conversion and selectivity was obtained when Na 2 CO 3 (5 mol‐%) was added to the reaction mixture. The Cu 0 acts as a supplementary activator and reducing agent in a SARA‐ATRC process. The protocol was extended to the cyclisation onto alkynes and the formation of β‐lactams, although these reactions gave lower yields (35–76 %).