Efficient and green route to gamma-lactams by copper-catalysed reversed atom transfer radical cyclisation of alpha-polychloro-N-allylamides, using a low load of metal (0.5 mol%)

The cyclisation of N-allyl-N-substituteda- polychloroamides is efficiently obtained through a copper-catalysed activators regenerated by electron transfer–atom transfer radical cyclisation process, with a metal load of only 0.5 mol%. The redox catalyst is introduced in its inactive form as copper( II) chloride/[nitrogen ligand] complex, and continuously regenerated to the active copper(I) chloride/[ nitrogen ligand] species by ascorbic acid. To preserve the catalyst integrity, the hydrochloric acid, released after each regeneration cycle, has been quenched by carbonate. The choice of the solvent is critical, the best performance being observed in ethyl acetate-ethanol (3:1).