Nickel-catalyzed coupling of CO2 and amines:: improved synthesis of carbamates

The electrochemical incorporation of carbon dioxide into amines catalyzed by an electrogenerated Ni complex afforded carbamates in moderate yields under very mild conditions (p(CO2) = 1 atm, room temperature) without any addition of probases. Mechanistic and electrochemical studies revealed the role of reduced nickel species in the activation of CO2 and electrogenerated CO2 center dot- as a base in the synthesis of carbamates. The influence of number of faradays per mole of amine supplied to the electrodes (Q), cathode materials, temperatures, supporting salts and amounts of catalyst was studied to optimize the electrolytic conditions. A plausible reaction mechanism for the reduction Of CO2 was proposed. Copyright (c) 2007 John Wiley & Sons, Ltd.