Mechanistic Insight into Weak Base‐Catalyzed Generation of Carbon Monoxide from Phenyl Formate and Its Application to Catalytic Carbonylation at Room Temperature without Use of External Carbon Monoxide Gas

Abstract The mechanisms of the weak base‐catalyzed generation of carbon monoxide (CO) and phenol from phenyl formate were investigated by experimental and theoretical methods. Kinetic studies revealed a first‐order reaction in both phenyl formate and the base. The reaction was found to proceed by an E2 α‐elimination pathway, which involves the abstraction of the formyl proton of phenyl formate, simultaneously generating CO and phenoxide. The reaction rate was affected by the substituents on phenyl formate, the polarity of solvents, and the basicity of bases. The mechanistic insight obtained from these studies permitted the chemical control of the rate of CO generation, which was the key to the development of the external CO‐free Pd‐catalyzed phenoxycarbonylation of haloarenes at room temperature. Because of the mild reaction conditions and wide substrate scope, this phenoxycarbonylation constitutes a general, safe, and practical method to synthesize arenecarboxylic acid esters. magnified image