Catalytic synthesis of dimethyl carbonate and its application as a green reagent for the synthesis of aromatic carbamates

Abstract

Dimethyl carbonate (DMC), is an important intermediate and is widely used in industry due to its non-toxicity, good biodegradability, and excellent solubility.1 DMC is used as an alternative, to harmful phosgene for the synthesis of aromatic polycarbonates and isocyanates and also as a carbonylation agent; DMC is about 1000 times less toxic than phosgene. It is also use in methylation reaction as a safe substitute for dimethyl sulfate, methyl halides; which are toxic and corrosive.2 Moreover, because of its versatile chemical properties, DMC is used as an electrolytic solution in secondary lithium battery, foodstuff flavoring agent and as a solvent in the field of paints. Owing to all these properties DMC is considered as an environmentally benign chemical and a safe reagent for many important transformations.3 Future demand for DMC is expected to grow in view of the stringent environmental regulations.Hence research work is being carried out on the development of safer routes for DMC synthesis and it’s utilization to value added products i.e. aromatic carbamates by methoxycarbonylation of aromatic amines.4 Methyl N-phenyl carbamate (MPC) is the simplest aromatic carbamate, are widely used as intermediates in the synthesis of pesticides, insecticides, herbicides, plastics and often used as protecting groups for amine functionality.5 MPC is an important precursor for preparing methylene diphenyl diisocyanate (MDI) by condensation of MPC with formaldehyde, which is an important intermediate for the synthesis of polyurethanes(PUs).6 PUs are among the most valuable polymers produced by the chemical industry. In 2007 the global consumption of PUs as raw material was about 12 million metric tons/year and the average annual growth rate is about 5%.