Electrooxidative Desulfurization/Chlorination. A Facile Synthesis of 4-Chloro-2-azetidinones, a Potent Intermediate for Carbapenems

(3S,4R)-3-(1'(R)-tert-Butyldimethylsilyloxyethyl)-4-chloro-2-azetidinone (2), a potent intermediate for the synthesis of carbapenem antibiotics, was synthesized by thermal ring opening/acylation of (3S,5R,6S)-6-(1'(R)-tert-butyldimethylsilyloxyethyl)penicillanate S-oxide (8) leading to 4-acylthio-2-azetidinone derivative 9 and subsequent removal of the N-substituent followed by electrooxidative desulfurization/chlorination of the C(4)-acylthio moiety.