A Facile and Green Approach for the One‐Pot Multicomponent Synthesis of 2,4,5‐Triaryl‐ and 1,2,4,5‐Tetraarylimidazoles by Using Zinc‐Proline Hybrid Material as a Catalyst

Abstract

A concise, green, highly versatile and selective one‐pot synthesis of 2,4,5‐triarylimidazoles and 1,2,4,5‐tetraarylimidazoles is reported in this paper. This methodology involves the condensation of bezil or benzoin with various aldehydes and ammonium acetate or aromatic amines in water : ethanol (4:1) mixture containing zinc‐proline hybrid material (ZnPHM) as catalyst to afford various triaryl and tetraarylimidazoles. The facile and mild protocol eliminates the use of expensive and corrosive reagents, toxic solvents and ensures operational simplicity with easy workup. The prominent features of this protocol are avoidance of harsh reaction conditions, recyclability of the catalyst and excellent yields of the desired products after simple crystallization.

One‐Pot, Two‐Step Metal and Acid‐Free Synthesis of Trisubstituted Imidazole Derivatives via Oxidation of Internal Alkynes Using an Iodine/DMSO System

“…3‐(4,5‐Diphenyl‐1 H ‐imidazol‐2‐yl)‐1 H ‐indole (3m): Yield 91.0 mg (54 %); white solid; recrystallization solvent: ethanol; m.p. 215–220 °C.…”

Zinc‐Catalysed Multi‐Component Reactions: An Overview

“…A one‐pot tri‐ and tetra‐ arylimidazole synthesis was also developed by Kidwai and co‐workers but by using ZnPHM (zinc‐proline hybrid material).n The reaction utilised similar substrates as that of the above work in (4:1) water:ethanol medium and also employed benzoin as one of the reactants (Scheme ). The methodology utilises a green perspective towards imidazole synthesis and gained excellent yields of the product.…”

Green Lewis Acid Catalysis in Organic Reactions

“…Solid acid catalysts have been extensively explored in green chemistry to synthesize various fine and large organic compounds with harsh liquid inorganic acids. [5,6] Due to their good selectivity, non-corrosive nature, high recyclability, and low toxicity, these catalysts have emerged as cost-effective alternatives for various organic transformations. [7,8] In general, these acid catalysts have good turnover numbers and are easily separated from the reaction medium.…”

“…They are also inexpensive, have high catalytic capacity, and can be used in a variety of ways. Solid acid catalysts have been extensively explored in green chemistry to synthesize various fine and large organic compounds with harsh liquid inorganic acids [5,6] . Due to their good selectivity, non‐corrosive nature, high recyclability, and low toxicity, these catalysts have emerged as cost‐effective alternatives for various organic transformations [7,8] .…”