[Et₃NH][HSO₄] catalyzed solvent‐free synthesis of new 1,2,3‐triazolidene‐indolinone derivatives

Abstract

A series of new 1,2,3‐triazolidene‐indolinone derivatives (17a‐j) were designed and synthesized via [Et3NH] [HSO4] catalyzed solvent‐free approach. The synthesis strongly relied on Knoevenagel condensation of 1,4‐disubstituted 1,2,3‐triazolyl aldehydes (15a‐j) and oxindole (5). The solvent‐free approach and Brønsted acidity of [Et3NH] [HSO4] ionic liquid increased the rate of reaction and provided the corresponding 1,2,3‐triazolidene‐indolinone derivatives (17a‐j) in excellent yields. The reusability of ionic liquid is also established with persistent effective yields up to four cycles. These novel 1,2,3‐triazolidene‐indolinone derivatives may exhibit potential biological response due to the presence of potent moieties and presence of triazolidene‐exocyclic double bond.

Exploring the Synthetic and Antioxidant Potential of 1,2‐Disubstituted Benzimidazoles Using [Et3NH][HSO4] Ionic Liquid Catalyst

“…[49] This IL works as an efficient and eco-benign catalyst in various organic transformations such as synthesis of tetrahydropyrimidine, benzoxanthenones, xanthenes, N-heterocyclic carbenes, and cyclic carbonates. [50][51][52][53][54][55][56][57][58][59][60][61][62][63] In continuation of our research to develop a sustainable and green synthetic protocol of bioactive nitrogen-based heterocycles via applying green catalyst [64][65][66][67] and due to the aforementioned drawbacks of the previously reported methods of benzimidazole, we envisioned the [Et 3 NH][HSO 4 ] IL catalyzed selective synthesis of 1,2-disubstituted benzimidazole under ambient conditions. To the best of our knowledge, this is the first time that [Et 3 NH][HSO 4 ] IL has been applied as a catalyst for the synthesis of 1,2-disubstituted benzimidazoles.…”

“…Bronsted acidic ionic liquid triethylammonium hydrogen sulfate [Et 3 NH][HSO 4 ] is a green catalyst and easily synthesized from simple and easily available amine and acid via acid‐base neutralization reaction [49] . This IL works as an efficient and eco‐benign catalyst in various organic transformations such as synthesis of tetrahydropyrimidine, benzoxanthenones, xanthenes, N‐heterocyclic carbenes, and cyclic carbonates [50–63] …”