The Mechanism of Carboxylative Cyclization of Propargylamine by N-Heterocyclic Carbene Complexes of Au(I).

Abstract The complex [Au(IPr)(2-oxazolidinone)] (1 = IKa) was prepared from reaction of [Au(IPr)Cl] (2), K2CO3, and propargyl amine (PPA). Kinetic studies have been performed for acid cleavage of 1 to yield the oxazolidinone product and an [Au(IPr)(X)] adduct. The fastest rates of cleavage were found to occur for the hydrogen chloride salt of PPA (PPA-HCl) and for the CO2 adduct of PPA, PPA-CO2 = the carbamic acid (CA). This transformation was studied as a function of [CA], pressure of CO2 as well as temperature. Detailed computational studies support the formation of a key intermediate and are also in agreement with a rapid carbonylation/decarbonylation reaction. The computed reactions mechanisms for addition of PPA-HCl and CA are also presented as well as the crystal structure of 1.