Incorporation of carbon dioxide into molecules of acetylene hydrocarbons on heterogeneous Ag-containing catalysts

The reaction between 2-(2-phenylethynyl)aniline and carbon dioxide on heterogeneous Ag-containing catalysts can lead either to benzoxazine-2-one or to 4-hydroxyquinoline-2(1Н)-one, depending on the reaction conditions (nature of the base, CO₂ pressure). The structures of the products were confirmed by ¹Н and ¹³С NMR spectroscopy. The maximum yield of the products (60 and 30% for benzoxazine-2-one and 4-hydroxyquinolin-2(1Н)-one, respectively) is achieved on the catalyst Ag(1%)/γ-Al₂O₃(F). According to the results of physicochemical studies, the high activity of the catalysts in the reactions proceeding via triple bond activation results from the combination of three factors. First, the catalyst contains metallic silver particles with the size >2 nm; second, metallic silver particles coexist with silver cations; and third, strong acid sites are present on the support surface.