Process for the synthesis of exomethylenecephams.

摘要

The present invention relates to a process for the preparation of exomethylene cephams, which are useful intermediates in the production of many useful beta -lactam antibiotics. More particularly there is provided a process for preparing a compound of formula I wherein n is O or 1, R1 is hydrogen atom or an organic residue and R2 is a carboxy protecting group, which process comprises reacting a compound of the formula II wherein X is halogen atom or acetoxy group and R1 n and R2 are as defined above with a lanthanide complex.