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

Abstract

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.