Highly Selective Synergistic N-Alkylation of Amines with ROH Catalyzed by Nickel–Ruthenium

Abstract

The synthesis of secondary amines through N-alkylation is particularly attractive. Conventional N-alkylation reactions usually provide undesired byproducts imines or/and tertiary amines, and discovery of high-selective transformations that can minimize byproducts remains a challenge. Herein, a reusable nickel−ruthenium catalyst Ni/Ru@SBA was developed exhibiting ideal selectivity toward N-monoalkylation of alcohols with amines, and no formation of byproducts imines or/and tertiary amines occurred. Mechanistic studies proved that the N-alkylation reaction is a reversible cascade mechanism. Based on the oxidation of alcohols to form aldehydes and the complex Ni/Ru@SBA[2H], what followed is the aldamine condensation into unstable intermediates which later obtained hydrogen from Ni/Ru@SBA[2H] to finally form secondary amines. The experimental reality is that solely with secondary amines under Ni/Ru@SBA in the presence of H 2 O, the formation of the original aldehydes/alcohols and amines took place, disclosing why ideal product yields could hardly be achieved in the presence of H 2 O. The Ni/Ru@SBA along with the developed process allows the production of diverse secondary amines with ideal selectivity.

A facile, one-pot reductive alkylation of aromatic and heteroaromatic amines in aqueous micellar media: a chemoenzymatic approach

“…Another reversible procedure for the alkylation of primary amines using a heterogeneous Ni/Ru catalytic system was developed by Wang et al This procedure involves the in situ oxidation of alcohols, their condensation with primary amines and finally the reduction of the imine to afford the desired secondary amines. 8…”

Metal–organic framework-derived CoNx nanoparticles on N-doped carbon for selective N-alkylation of aniline

“…20,21 In addition, the use of expensive metals, ligands, and external additives makes the use of homogeneous catalysts impractical. 22 In this respect, heterogeneous noble metal catalysts of Pt, 23 Ru, 24,25 Pd, 26 Rh, 27 etc. have been used for N-alkylation of primary amines.…”

Copper(I) Chloride Mediated Amination of Halobenzenes via Azides: Scope, Mechanistic Aspects, and C–C Cleavage Reactions

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