A green way to g-lactams through a copper catalyzed ARGET-ATRC in ethanol and in the presence of ascorbic acid

A ‘green’ ARGET-ATRC, for the CuCl[PMDETA] catalysed cyclo-isomerization of N-allyl-a-polychloroamides to g-lactams is described. The process works efficiently (yields 78e96%), uses a bio-solvent, as ethanol, and exploits the reducing feature of ascorbic acid to limit, at a low level (2e4%), the amount of catalyst. To preserve the efficacy of the catalytic cycle, addition of Na2CO3 is essential, which quenches the HCl released during the CuCl[PMDETA] regeneration step. Profitable features of the process are: mild reaction tem-peratures (25e37 C), relatively short reaction times (usually 5 h) and low solvent volumes (2 mmol of substrate/mL of ethanol). The method, upon stoichiometric adjustment, was also used for the synthesis of a,b-unsaturated-g-lactams from N-(2-chloroallyl)-a-polychloroamides, via a tandem process involving an ATRC and a reductive [1,2]-elimination.