A simple and efficient in situ generated ruthenium catalyst for chemoselective transfer hydrogenation of nitroarenes: kinetic and mechanistic studies and comparison with iridium systems

Abstract

A convenient and highly efficient in situ generated Ru(ii) system for synthesizing functionalized amines and mechanistic studies and comparison with iridium systems is presented.

Tandem Transformation of Nitro Compounds into N‐Methylated Amines: Greener Strategy for the Utilization of Methanol as a Methylating Agent

“…To shed some light on the mechanism of this tandem transformation, several experiments were carried out. We previously reported that complex 1 followed the direct route in transfer hydrogenation of nitrobenzene to aniline . During the course of this direct transformation of nitroarenes to N ‐methylamines, the corresponding azoarenes or azoxyarenes were not detected, indicating a preference for the direct route .…”

“…We previously reported that complex 1 followed the directr oute in transfer hydrogenation of nitrobenzenet oa niline. [15] Duringt he course of this direct transformation of nitroarenest oN-methylamines, the corresponding azoareneso ra zoxyarenes weren ot detected, indicating ap reference for the direct route. [21] To further teste this, azobenzene was treated under the optimized conditions, but gave only 5% conversion( Scheme 4a).…”

“…We recently reported ah ighly activei ns itu-generated Ru II catalystf or the chemoselective transfer hydrogenation (TH) of nitroarenes in 2-propanol. [15] As ap art of our continuingi nterest in the reduction of nitroarenes [16] and the utilization of alcohols as alkylating agents, [17] we report herein air-and moisture-stable, environmentally benign simple Ru II -catalyzed tandem and selective conversion of variousn itro compounds into the corresponding N-methylated amines by using methanol (Scheme 1).…”

“…We recently reported that, among the various ligands, 2-(6methoxypyridin-2-yl)-1,10-phenanthroline( phenpy-OMe) exhibited the highest activity in Ru II -catalyzed TH of nitroarenes. [15] Hence,w es tarted this work with [Ru(phenpy-OMe)-(MeCN) 2 Cl]Cl (1;S cheme 2) to test its potential in N-methylation of amines by using methanola nd accordingly optimized the reactionc onditions (see the Supporting Information) and the substrate scope is outlined in Ta ble 1. Various substituted anilines bearing Cl, Br,M e, OMe and OPh groups were converted into the corresponding N-methylated anilines (1a-g)i ne x-cellent yields.…”

Ruthenium(II)‐NNN‐Pincer‐Complex‐Catalyzed Reactions Between Various Alcohols and Amines for Sustainable C−N and C−C Bond Formation

“…All the commertial reagents and metal precursors were purchased from Sigma‐Aldrich, Alfa‐Aesar, Spectrochem, Avra, SDFCL and Arora Matthey India. The metal complexes were synthesized according to our previous work , . 1 H, 13 C and 31 P NMR spectra were recorded in JEOL Spectrometer.…”