Transition-metal-free Homogeneous Transformation Of CO₂into Carbamates

Utilization of carbon dioxide (CO2) have gained considerable attention due to its potential use as an attractive, abundant, and renewable C1source and its main contribution to global wanning. It is of paramount importance for organic chemists to build the new reaction system to efficiently and selectively transform CO2into value-added fine chemicals in transition-metal-free and mild conditions.Based on our previous experimental results, this thesis will build the new transition-metal-free carboxylative coupling reaction system bearing proton donor (primary amines), CO2and carboxylate acceptor (propargyl halides), explore the new method to stabilized the carbamic acids and synchronously maintain its reactivity, synthesize the carbamate compounds in highly efficient and chemoselective manner, and prepare the synthetically important intermediate through the electrophilic cyclization reactions of the carbamate products.The carboxylative coupling reaction of benzyl amine, CO2and3-chloro-1-phenyl-1-propyne was chosen as a model reaction to identify an effective reaction system and the optimum reaction conditions were established:propargyl halide (1equiv), CO2(0.2MPa), amine (2equiv), DBU (2equiv), DMF,60℃,12h. Under the optimized reaction conditions, a variety of functionalized carbamates were successfully synthesized in highly efficient and chemoselective manner. The preliminary study concerning on the electrophilic cyclization reactions of the carbamate products were also conducted.