Chemistry of O-silylated ketene acetals: an efficient synthesis of carbapenem and 1β-methylcarbapenem intermediates

3-(1-tert-Butyldimethylsiloxyethyl)-4-phenylsulfinylazetidin-2-one reacted smoothly with various types of O-silylated ketene acetals and silylated enol ethers in the presence of a catalytic amount of zinc iodide to give the corresponding trans-4-substituted azetidin-2-ones in good yields. The latter compounds are key intermediates for the synthesis of carbapenems and 1β-methylcarbapenems.