Synthesis of 3-Hydroxycephems from Penicillin G through Cyclization of Chlorinated 4-Phenylsulfonyl-thio-2-azetidinones Promoted by a BiCl₃/Sn or TiCl₄/Sn Bimetal Redox System

Tanaka, H.; Taniguchi, M.*; Kameyama, Y.; Monnin, M.; Torii, S.; Sasaoka, M.*; Shiroi, T.*; Nagao, S.*; Yamada, T.*; Tokumaru, Y.* (*Tokushima Research Laboratories,Otsuka Chemical Co., Ltd.), Bull. Chem. Soc. Jpn. 1995, 68, 1385.

A novel access to 3-hydroxycephems was attained from penicillin G via the C=C bond cleavage of 1-(1-alkoxycarbonyl-2-chloromethyl-2-propenyl)-4-phenylsulfonylthio-2-azetidinones by successive treatment with RuCl₃/HIO₄ and HIO₄/CuSO₄ and reductive cyclization of 1-(1-alkoxycarbonyl-3-chloro-2-hydroxy-1-propenyl)-4-phenylsulfonylthio-2-azetidinones on treatment with a newly devised BiCl₃/Sn or TiCl₄/Sn bimetal redox couple in DMF containing pyridine.