N-Methylation of amines with methanol in a hydrogen free system on a combined Al₂O₃–mordenite catalyst

Abstract

N-Methyl amines play a major role in the production of medicines, pesticides, surfactants and dyes. N-Methylation of primary or second amines with methanol is considered to be a green path for the synthesis of N-methyl amines and the catalyst is key. In this article, the combined Al 2 O 3 -mordenite catalyst (mass fraction of alumina is 40%) with good activity, selectivity, lifetime and stability was prepared for N-methylation of various amines with methanol in a hydrogen free system in a fixed bed reactor, and characterized by XRD, N 2 adsorption and NH 3 -TPD. Furthermore, the methanol adsorption was investigated by in situ FTIR, and the result indicated that methoxyl species may be the active species for the N-methylation of amines.

Photocatalytic N-Methylation of Amines over Pd/TiO2 for the Functionalization of Heterocycles and Pharmaceutical Intermediates

“…8 Examples of recently developed catalysts include ruthenium, 9,10 iridium, 11-13 iron 14 and manganese 15,16 complexes, and heterogeneous catalysts (Scheme 2b). [17][18][19] These catalysts could be used for the efficient synthesis of secondary aromatic or tertiary aliphatic methylamines bearing heteroaryls such as pyridine, pyrimidine, and thiophene. 7,8a,8b,8d,10,11c Whereas most of these methods are effective for methylation of (hetero)aromatic amines, however, methylation of aliphatic amines with heteroaryl functionalities has been rare (Scheme 2b).…”

“…Because of such importance, the catalytic N-methylation of amines employing methanol as a methylation agent has been extensively explored . Examples of recently developed catalysts include ruthenium, , iridium, − iron and manganese , complexes, and heterogeneous catalysts (Scheme b). − These catalysts could be used for the efficient synthesis of secondary aromatic or tertiary aliphatic methylamines bearing heteroaryls such as pyridine, pyrimidine, and thiophene. ,,, c Whereas most of these methods are effective for methylation of (hetero)­aromatic amines, however, methylation of aliphatic amines with heteroaryl functionalities has been rare (Scheme b) . Furthermore, these reactions have generally required harsh reaction conditions (typically ≥ 100 °C) and the presence of strongly basic additives (e.g., t -BuOLi, t -BuOK, NaOH).…”

Sustainable and Selective Monomethylation of Anilines by Methanol with Solid Molecular NHC-Ir Catalysts

“…As an important biomass and cost-effective feedstock fine chemical, methanol has also been utilized for this purpose. Various Lewis acids have demonstrated their catalytic efficiency in the N- methylation of amines with MeOH, although harsh reaction conditions are still required to achieve satisfactory results for fully methylated products. − Recently, Saito and co-workers reported a room temperature N -methylation by using Pd/TiO 2 or Ag/TiO 2 as nanophotocatalysts. Besides fully methylated products are produced in the presence of primary amine substrates, however, the recyclability of the heterogeneous catalyst is not addressed in their studies.…”

Continuous N-alkylation reactions of amino alcohols using γ-Al2O3 and supercritical CO2: unexpected formation of cyclic ureas and urethanes by reaction with CO2

“…Another approach to N -alkylation in which water is the only byproduct is the direct substitution of alcohols with amines. It is an attractive method; however, it requires significant activation of the alcohol or amine to proceed efficiently, and often a heterogeneous catalyst at elevated temperature and/or pressure is employed [ 20 – 28 ]. As these reactions are mostly carried out in high pressure systems, they are particularly suitable for the use of supercritical solvents.…”