Sulfur Catalyzed Metal‐ and Solvent‐Free ABB'C Four‐Component Synthesis of N‐Arylidene‐2‐aryl‐imidazo[1‐2‐a]azin‐3‐amines via Strecker Reaction

Abstract

An efficient ABB'C four-component Strecker reaction between 2-aminopyridines, aromatic aldehydes and trimethylsilyl cyanide (TMSCN) was developed under metal-and solvent-free conditions to access N-arylidene-2-aryl-imidazo[1,2-a]azin-3amines in high yields. This one-pot reaction was carried out in the presence of elemental sulfur as catalyst using readily available starting material at room temperature. The reaction was tolerant to several substituted 2-aminopyridines and aryl aldehydes and have good green chemistry metrics as compared to the reported methods.

Metal- and Solvent-Free Synthesis of m-Terphenyls by an Iodine-Catalyzed Tandem Formal [3+3]-Cycloaddition/Oxidation

“…As part of our ongoing interest in developing novel strategies for the construction various biologically significant framework under metal-free conditions, we have employed elemental sulfur in a synthesis of 2 H -pyrido[1,2- a ]pyrimidin-2-ones 19a and a four-component synthesis of N -arylidene-2-aryl-imidazo[1,2- a ]azin-3-amines. 19b Sulfur has been employed as a catalyst for several transition-metal-free syntheses of heterocycles and, due to its variable oxidation state, it can be used as an oxidant/co-oxidant and has been found to possess mild Lewis acidity. 20 21 In this context, we surmised that it might be possible to employ sulfur as a reagent in a [3+3]-cycloaddition of chalcones with β-enamine esters to give substituted m -terphenyls.…”

A Catalyst‐ and Solvent‐ Free Synthesis of Tetra‐Substituted Pyrroles by Multicomponent Reaction

“…In continuation with our efforts on developing novel strategies for the synthesis of various biologically important frameworks under metal‐free conditions, we have employed elemental sulfur as catalyst for the synthesis of 2 H ‐pyrido[1,2‐ a ]pyrimidin‐2‐ones [20a] and N ‐Arylidene‐2‐aryl‐imidazo [1‐2‐ a ]azin‐3‐amines [20b] and as oxidant in I 2 catalysed synthesis of substituted m ‐terphenyls [20c] . Herein, we aim to develop a facile, environmentally benign and effective synthesis of tetra‐substituted pyrroles from readily available starting materials such as arylamines, β‐oxo esters and β‐nitroolefins under metal‐ and solvent‐free condition.…”