Selective N-methylation of primary aliphatic amines with dimethyl carbonate in the presence of alkali cation exchanged Y-faujasites

The N-methylation of aliphatic amines [XC6H4(CH2)nNH2; n=1, X=H (1a), o-MeO (1b), p-MeO (1c); n=2, X=H (2a), o-MeO (2b); 1d: PhCH(Me)NH2] with dimethyl carbonate (DMC) is efficiently catalysed by NaY faujasite: on condition that CO2 (a co-product of the reaction) is carefully removed, N-methyl- and N,N-dimethyl-amines (RNHMe and RNMe2) are obtained in good overall yields (70–90%). Otherwise, in the presence of CO2, carbamates (RNHCO2Me) form competitively to a large extent. The reaction probably proceeds through a BAl2 displacement of the amine on DMC.