Synthesis of β‐Lactams by 4‐exo‐tet Cyclization Process Induced by Electrogenerated Cyanomethyl Anion,Part 2:[1] Stereochemical Implications

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