Azomethine-isocyanide [3+2] cycloaddition to imidazoles promoted by silver and DBU

Abstract

A new silver-promoted [3+2] cycloaddition of azomethine ylides with isocyanides has been described. The methodology provides an efficient and modular approach to 1,2,4-trisubstituted imidazoles of vital bioactive molecules and atypical antipsychotics analogues.

Silver‐Catalyzed [3+2] Cycloaddition of Azomethine Ylides with Isocyanides for Imidazole Synthesis

“…However, when the temperature was further elevated to 60 °C, a silver mirror was observed and 3aa was obtained in 38% yield even when the reaction time was prolonged to 12 h (Table , entry 3). This result is consistent with Bi's finding that one equivalent of Ag 2 CO 3 was needed when the reaction was performed at higher temperatures . Decreasing the amount of Ag 2 CO 3 to 20 mol% led to a lower yield (Table , entry 4).…”

“…Although the syntheses of imidazolidines and saturated NHC‐Au(I) complexes via cycloaddition of azomethine ylides have been documented [Scheme , Eqs. (2) and (3)], the catalytic synthesis of imidazoles from the cycloaddition of azomethine ylides and isocyanides has not been reported . During the course of our studies of isocyanide‐based annulations and inspired by Hashmi's work, we developed a one‐step silver‐catalyzed aerobic oxidative 1,3‐dipolar cycloaddition of azomethine ylides with isocyanides for the efficient and practical synthesis of 1,2‐diarylimidazoles (Scheme , bottom ).…”

Synthesis of 1,2,4-Trisubstituted-(1H)-imidazoles through Cu(OTf)2-/I2-Catalyzed C–C Bond Cleavage of Chalcones and Benzylamines

“…Because of the significant applications, several classical methods for the synthesis of imidazole are available. 25 A series of metal-catalyzed 26 and nonmetal-catalyzed 27 multicomponent reactions have also been reported in the recent years. Accordingly, we envisaged that the development of a new and simple strategy using readily available chalcones and benzylamines, which use inexpensive catalysts for the construction of 1,2,4-trisubstituted-(1 H )-imidazoles, would be a valuable contribution to a limited number of existing approaches (Scheme 1).…”

Recent Progress in Synthesis of Polysubstituted Imidazoles by Cyclization Reaction

“…2017 年, 毕锡和课题组 [74] 报道了一种银促进的亚 同年, 宋秋玲课题组 [78] 报道了一种通过[3＋1＋1] 型环化反应合成咪唑的简便方法(Scheme 60). 该反应 是在 CuCl 2 和 1,10-邻菲罗啉的存在下, 使用 Cs 2 CO 3 作 为碱, CH 3 CN 作为溶剂, 在 100 ℃、氮气下, 通过原位…”