A Convenient Access to 2-exo-Methylenecephem

Tanaka, H.; Kameyama, Y.; Sumida, S.-i.; Shiroi, Y.; Sasaoka, M.; Taniguchi, M.; Torii, S. Synlett 1992, 351.

One-pot transformation of 3-methyl-2-(2-oxo-4-phenylsulfonylthio-1-azetidinyl)-2,4-pentadienoates 8, derived from penicillins, into 2-exo-methylenecephems 1 has been achieved by successive treatment with sodium benzenesulfinate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in dimethylformamide.