Ring-opening process for preparing azetidinone intermediates

摘要

Compounds of formula I <IMAGE> (I) wherein R1 and R2 is each H, halo or an organic group, R3 is H or organic group, n=1 or 2, M is a heavy mono- or divalent metal, or M2A wherein M2 is a heavy divalent metal and A is an organic or inorganic group, are prepared by treating a starting penicillin in a solvent with a salt of M1 or M2A in the presence of a base at a temperature of from -70 DEG to 100 DEG C.