Selective N-Methylation of Aliphatic Amines with CO₂ and Hydrosilanes Using Nickel-Phosphine Catalysts

Abstract

A method using CO2 and PhSiH3 for the methylation of primary and secondary aliphatic amines catalyzed by Ni (0) complexes was developed, selectively producing the monomethylated products in moderate to good yields. For that purpose, two catalysts were used: [(dippe)Ni(μ-H)]2 and the commercially available Ni(COD)2/dcype, both of which were rather efficient in this process. With a slight experimental modification, the reaction allowed the production of monomethylated ureas in good yields by using low amounts of PhSiH3. On the basis of the experimental results, we propose a possible reaction mechanism for the formation of the new C–N bond.

Mechanistic Insights on the Reduction of CO2 to Silylformates Catalyzed by Ir‐NSiN Species

“…[3a] Therefore, the development of active and selectivec atalytic systemsf or the reduction of CO 2 with silanes is of great interest. Some examples of catalytic systems that allow the selective reduction of CO 2 with hydrosilanes or hydrosiloxanest og ive the corresponding silylformate, [4][5][6][7][8][9][10][11][12] bissilylacetal, [13] methoxysilane, [14] or methane [15] are known. Particularly,s ilylformates have attracted attention during the last recenty ears owing to their potentialu se as aC 1s ource in organic synthesis.…”

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

“…Recently, alternative methodologies have been reported based on the use of CO 2 as a methylating reagent. 7 Organocatalysts have also been shown as efficient promoters of this transformation. It is potentially the most attractive C 1 feedstock to introduce carbon into molecules.…”

1,4‐Dioxane‐Tuned Catalyst‐Free Methylation of Amines by CO2 and NaBH4

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Ac atalyst-free reductive functionalization of CO 2 with amines and NaBH 4 was developed. For example, metal-based catalytic systems including alkali metals such as cesium, [6] inexpensive transition metals such as Fe, [7] Cu, [8] Zn, [5] and Ni, [9] ,a nd noble metals such as Ru, [4, 10] Pd, [11] Pt, [12] and Au [13] have been used in such reactions, as have organic and inorganic molecular catalysts, such as N-heterocyclic carbenes, [14] carbodicarbene, [15] proazaphosphatrane superbases, [16] B(C 6 F 5 ) 3 , [17] tetrabutylammonium fluoride (TBAF), [18] glycine betaine, [19] carboxylate, [6] and tungstate. Notably,t he six-electron reduction of CO 2 to form the methyl group occurred simultaneously with formationo f the CÀNb ond to give the N-methylated amine.

Methylamines are important chemicals and core structures in many industrial products, such as medicines, natural products, and dyes.

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