Efficient and “Green” Synthetic Route to Imidazo[1,2-a]pyridine by Cu(II)–Ascorbate-Catalyzed A³-Coupling in Aqueous Micellar Media

Abstract

An efficient and environmentally sustainable method for the synthesis of imidazo[1,2- a ]pyridine derivatives by domino A 3 -coupling reaction catalyzed by Cu(II)–ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO 4 with sodium ascorbate and aided a facile 5- exo -dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2- a ]pyridines in good overall yields. A simple experimental setup, water as the “green” medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.

Hydromagnesite sheets impregnated with cobalt–ferrite magnetic nanoparticles as heterogeneous catalytic system for the synthesis of imidazo[1,2-a]pyridine scaffolds

“…According to the literature and our results, 11,14,22,25,31–35 a plausible reaction mechanism to account for the formation of imidazo[1,2- a ]pyridines is presented in Scheme 3 . The domino reaction begins with condensation between 2-aminopyridine (1a–b) and the pertinent aryl aldehyde derivatives (2a–e), followed by dehydration, resulting in the formation of a Schiff base (A).…”

“…A systemic perusal of the literature revealed that there are recent reports on several transition-metal-catalyzed techniques for the synthesis of imidazole-fused heterocyclic core nuclei. These catalytic strategies include the use of CuSO 4 ·5H 2 O, 11 MNP@BiimCu, 12 CuO/CuAl 2 O 4 , 13 Fe 3 O 4 @SiO 2 NPs, 14 CuI/ l -proline, 15 Cu–NPs 16 and nano-copper/nano-ZnAl 2 O 4 under an N 2 atmosphere, 17 PW-CIS500, 18 and CoFe 2 O 4 @CNT-Cu 19 towards the green synthesis of amalgamated heterocyclic moieties. However, these reported methods have some bottlenecks including the use of hazardous and expensive catalysts, extensive moisture-sensitive metallic reagents, harsh reaction conditions, prolonged reaction time, tedious work-up processes, use of volatile organic solvents and non-recyclable and large catalytic loading, leading to the generation of an enormous amount of waste.…”

Recent developments and perspectives in the copper-catalyzed multicomponent synthesis of heterocycles

“…Imidazo[1,2- a ]pyridine derivatives were prepared by Cu( ii ) ascorbate catalyzed domino A 3 -coupling reaction in aqueous micellar media in the presence of anionic surfactant, sodium dodecyl sulfate (SDS) ( Scheme 30 ). 39 In this eco-friendly procedure, the catalyst used was a dynamic combination of Cu( ii )/Cu( i ), which was generated in the reaction mixture in situ by mixing CuSO 4 with sodium ascorbate. Imidazo[1,2- a ]pyridines were synthesized in good amount from 5- exo -dig cycloisomerization of alkynes with the condensation products of aldehydes and 2-aminopyridines.…”

Application of 2-Aminopyridines in the Synthesis of Five- and Six-Membered Azaheterocycles

“…通常, 通过一锅法多组分反应绿色高效地制备目标 分子是化学工作者的追求 [34] . 以 2-氨基吡啶、芳香醛和 末端炔烃为底物, 一锅法得到芳香醛中芳环位于咪唑环 的 2-位而非 3-位的产物 [35] . 例如, Rawat 课题组 [36] 以 CuIn 2 掺杂的石墨烯量子点为催化剂, 三组分经历了生 成五元环的 5-exo-dig 分子内环化反应, 得到了 2,3-二芳 基取代咪唑并[1,2-a]吡啶(Scheme 6).…”