Catalytic synthesis of β-lactam derivatives by carbonylative cycloaddition of acylsilanes with imines via a palladium Fischer-carbene intermediate

Abstract

AbstractFischer-type carbene complexes are characterized by the presence of a π-donating group, such as an alkoxy group on the carbene carbon. Despite the notable progress that has been made in synthetic methods that involve the use of Fischer-type carbene complexes, stoichiometric amounts of carbene complexes are still required for such reactions and catalytic variants remain elusive. This limitation primarily stems from the lack of suitable carbene precursors, which is in sharp contrast to the fact that carbene complexes bearing an electron-withdrawing group can be readily generated from the corresponding diazo esters. Here we report that acylsilanes can function as a precursor for a Fischer-carbene complex by the action of a palladium catalyst. This system can be used in catalytic carbonylative cycloaddition reactions with imines to form densely substituted β-lactam derivatives. A key siloxycarbene–palladium intermediate complex was isolated and successfully characterized by X-ray crystallography.