Synthesis of beta-lactams by 4-exo-tet cyclization process induced by electrogenerated cyanomethyl anion, part 2. Stereochemical implications

An efficient electrochemically induced synthesis of chiral cis b-lactams has been described, via deprotonation of chiral amides containing an acidic methylene group and a bromine atom as leav- ing group and bearing a chiral auxiliary or amine function. The electrogenerated base – cyanomethyl anion – is easily obtained by galvanostatic reduction of acetonitrile-tetraethylammonium hexafluorophos- phate solutions under very mild conditions. The yields are high and the cis-diastereoselection com- plete. The use of starting chiral amides has allowed in many cases the preparation of the most abundant isomer in a pure form.