Reaction of N-methylformamide with dimethyl carbonate: a DFT study

The detailed analysis of the mechanism of metathesis of N-methylformamide with dimethyl carbonate leading to the formation of N, O-dimethylcarbamate was carried out using the B3LYP/6-311++G(df,p), B3LYP-D3(BJ)/6-311++G(df,p) and ωB97XD/6-311++G(df,p) density functional methods. The reactions proceed in three stages. The first step consists in the tautomeric conversion of N-methylformamide to iminol. The second stage, which is the rate-limiting step, involves the addition of dimethyl carbonate via the N=C π-bond of iminol. The third stage of the reaction is the cleavage of the methyl formate molecule from N-methyl-N-[(hydroxy)(methoxy)methyl]-O-methylcarbamate. This conversion results in the formation of N, O-dimethylcarbamate. All stages of the reactions are catalyzed by associates of alcohols, which lead to a strong decrease in activation enthalpies.