The Methodology Of C-N Bond Formation With Carbon Dioxide As Synthon

Carbon dioxide is the most abundant greenhouse gas and can be also regarded as a typical renewable natural resource. The development of environmentally friendly process utilizing CO2 has received much attention from the viewpoint of resources utilization and green chemistry. In this context, one of the major successes is the utilization of CO2 as the starting materials to prepare oxazolidinones, urea and carbamate via the coupling of CO2 with amines in view of green chemistry.2-Oxazolidinones are an important class of five-membered heterocycles showing a plethora of applications as intermediates and chiral auxiliaries in organic synthesis. Cycloaddition of CO2 with nitrogen source and olefin is one of the most promising methods for synthesis of oxazolidinones. We have developed a binary catalyst system composed of n-Bu4NBr3/n-Bu4NBr for facile synthesis of 5-substituted 2-oxazolidinones with perfect regioselectivity in a single operation directly from olefins, Chloramine-T and CO2. The choice of efficient binary catalysts for two steps, i.e. aziridination and cycloaddition, and the optimization of reaction condition are keys to the one-pot synthesis of 5-substituted 2-oxazolidinones. A possible mechanism for the present one-pot synthesis of oxazolidinones was also proposed.Urea derivatives are an important class of carbonyl compounds and useful chemical intermediates in the synthesis of Pharmaceuticals, agricultural chemicals, dyes; and they are also used as antioxidants in gasoline and additives in plastics. Therefore, the synthesis of ureas starting from CO2 has drawn much attention because CO2 is a renewable, abundant, cheap, and non-toxic source of functional carbon unit. We have developed polyethylene glycol-supported potassium hydroxide (KOH/PEG1000) as a recyclable catalyst for facile synthesis of urea derivatives from amines and CO2 without utilization of additional dehydrating agents. Primary aliphatic amines, secondary aliphatic amines and diamines can be converted into the corresponding urea derivatives in moderate yields. Furthermore, the catalyst can be recovered after a simple separation procedure, and reused over 5 times with retention of high activity.Organic carbamates hold extensive applications in pharmaceutical industry, agriculture and have been widely used as key intermediates or protecting groups in synthetic chemistry. We have developed an efficient and environmentally benign method for the synthesis of organic carbamates. Amines, CO2 and alkyl halides underwent a three-component reaction with the aid of K2CO3 and polyethylene glycol (PEG400, MW=400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent, phase transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.