NOVEL SYNTHESIS OF PYRROLIDINONES BY COBALT CARBONYL CATALYZED CARBONYLATION OF AZETIDINES - A NEW RING-EXPANSION CARBONYLATION REACTION OF 2-VINYLAZETIDINES TO TETRAHYDROAZEPINONES

Pyrrolidinones can be synthesized in high yields and regioselectivity by the cobalt carbonyl catalyzed carbonylation of azetidines. For 2-substituted azetidines (alkyl, aryl, CH2OH, CH2OR, CH2OCOR, and COOR), carbonyl insertion occurs in the more or less substituted ring carbon-nitrogen bond depending on the kind of substituent group and on the reaction temperature. In the case of 2-vinylazetidines, ring expansion and carbonylation affords seven-membered-ring tetrahydroazepinones. Good functional group tolerance was observed in these reactions.