Trapping of carbamic acid species with (trimethylsilyl)diazomethane

Methoxycarbonylation of a variety of amines into the corresponding methyl carbamates was accomplished by allowing them to react with (trimethylsilyl)diazomethane TMSCHN2 under bubbling of CO2. The reaction was performed at room temperature for a period of ca. 2 h in benzene–MeOH (4/1 v/v), which was the solvent of choice. In this mixed solvent, undesirable bicarbonate is formed in equilibrium along with carbamate anion. Owing to the irreversibility in the esterification step by TMSCHN2, however, the yield of methyl carbamate can reach very high.