Safe and Efficient Reductive Methylation of Primary and Secondary Amines UsingN-Methylpyrrolidine Zinc Borohydride

A versatile way for the synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with the NaBH4/I2 system

An economical and versatile protocol for the one-pot synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with NaBH₄/I₂ in THF at reflux temperature is described. This method used no special catalyst and various monomethylamines can be easily obtained in moderate to good yields from a wide range of raw materials including amines (primary amines and secondary amines), carboxylic acids and isocyanates. Besides, an interesting reduction selectivity was observed. Exploration of the reaction process shows that it undergoes a two-step pathway via a formamide intermediate and the reduction of the formamide intermediate to monomethylamine as the rate-determining step. This work can contribute significantly expanding the applications of N-substituted carbonylimidazoles.

A general protocol for the reductive N-methylation of amines using dimethyl carbonate and molecular hydrogen: mechanistic insights and kinetic studies

A general and selective ruthenium-catalyzed reductive N-methylation of primary and secondary aromatic and aliphatic amines using dimethyl carbonate as a C₁ source and molecular hydrogen as a reducing agent is reported for the first time.

N-heterocyclic carbene copper(I) catalysed N-methylation of amines using CO2

The N-methylation of amines using CO2 and PhSiH3 as source of CH3 was efficiently performed using a N-heterocyclic carbene copper(i) complex. The methodology was found compatible with aromatic and aliphatic primary and secondary amines. Synthetic and computational studies have been carried out to support the proposed reaction mechanism for this transformation.