Nucleophilic Metal Complexes as Acylation Catalysts: Solvent-Dependent “Switch” Mechanisms Leading to the First Catalyzed Staudinger Reaction

Abstract
Catalytic acylation using complex transition metal salts MCo(CO)4 is demonstrated. Surprisingly, a solvent-dependent mechanistic “switch” results in a Lewis acid-based acylation mechanism in nonpolar media and a nucleophilic mechanism in polar organic media. These observations lead to the first example of a catalyzed Staudinger reaction to form β-lactams.