Reductive N-methylation of amines using dimethyl carbonate and molecular hydrogen: Mechanistic insights through kinetic modelling

Abstract

Kinetic analysis of ruthenium-catalyzed reductive N-methylation of amines using dimethyl carbonate as C1 source and molecular hydrogen has been performed. Kinetic equations have been derived and kinetic modelling has been performed for experimental data generated previously at a constant hydrogen pressure as well as for additional experiments performed at different hydrogen pressures. The study has revealed interesting kinetic features related to an induction period strongly influenced by temperature. A kinetic model has been proposed based on advanced reaction mechanism featuring transformation between different type of catalytic species and inactivation of them during the reaction. Kinetic modelling was done for all data sets together showing excellent correspondence between calculations and experiments.

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors

“…As for DMC aminolysis, carbamoylation and methylation are the two main reactions, which are strongly affected by reaction temperatures. 2,[16][17][18] It was generally reported that incorrect increasing of reaction temperature could enhance methylation, resulting in a decrease of MPC selectivity. Thus, reaction temperature is optimized rstly (the molar ratio of DMC to aniline is 20, and reaction time is 7 h, Fig.…”

“…15 However, due to the high reactivity of the intermediates decomposed from DMC, carbamoylation and methylation proceed simultaneity during the aminolysis reaction, which, respectively, leads to the formation of MPC and N-methylaniline (NMA) and/or N,N 0 -dimethylaniline (DMA), as shown in Scheme 1. 2,[16][17][18] Thus, developing catalysts with high activity is quiet necessary so as to enhance the selectivity as well as yield of MPC.…”

Catalytic Reductive N‐Alkylations Using CO2 and Carboxylic Acid Derivatives: Recent Progress and Developments

“…[5] In 2016, Beller and co-workers reported the only example in which DMC has been used as am ethylating agent in the presence of H 2 as the reductant (Scheme 22). [64] A [Ru/Triphos/additive] catalyst combination was able to carry out the methylation of aromatic and aliphatic primary and secondary amines (more than 40 examples) using the carbonyl function of DMC as the methyl source.This process represents an improvement over the earlier described procedures for the same reaction but using silanes (see Scheme 5). [48] As previously mentioned, the use of carboxylic acids/ esters as alkyl sources in N-alkylation is attractive to produce av ariety of functionalized alkyl amines.I na ddition, the employment of H 2 as the reductant in combination with these alkyl sources is highly desirable.I n2 007, following this general idea, Cole-Hamilton and co-workers reported a[Ru/ Tr iphos]-catalyzed hydrogenation of nonanoic acid in the presence of ammonia, which afforded am ixture of nonylamine and dinonylamine,a lbeit in relatively low yields and selectivities.…”

Carboxymethylation of cinnamylalcohol with dimethyl carbonate over the slag-based catalysts

“…The concentration dependencies demonstrating an induction period in the carboxymethylation of cinnamylalcohol with DMC provide a strong argument in favor of using a concept of two catalytically active sites. The same approach was previously applied [55] for methylation of aniline with DMC as well where catalyst inactivation was also included in the reaction mechanism. A simplified reaction scheme is presented in Fig.…”