Carbamoylation of primary, secondary and aromatic amines by dimethyl carbonate in a flow system over solid catalysts

Abstract

Carbamate esters represent an important class of organic compounds which find wide application in chemical industry. Classical procedures for the preparation of carbamates are based on the reaction with a very risky compound - phosgene or phosgene derivatives. A phosgene-free flow-system synthesis of eight carbamates in the reaction of various amines with dimethyl carbonate has been presented. The influence of amine order and structure on their activity in the carbamoylation process was studied. Fe2O3, Fe2O3/SiO2, Fe2O3/CoO/NiO/SiO2, TZC-3/1 and T-4419 were used as catalysts for the process. The iron – chrome catalyst TZC-3/1 was found to be the most active leading to approx. 70% yield of methyl N-hexylcarbamate with an 80% selectivity in the reaction of n-hexylamine with dimethyl carbonate at 150°C.