Chitosan: An Efficient, Reusable, and Biodegradable Catalyst for Green Synthesis of Heterocycles

Abstract

A convenient and rapid method is described for the synthesis of nitrogen heterocyclic derivatives by one-pot three-component reaction of substituted aromatic aldehydes, dicarbonyl- and 2-aminobenzothiazole/3-amino-1,2,4-triazole/urea/thiourea using commercially available chitosan in 2% acetic acid in aqueous media at 60–65 °C. Chitosan was used as an efficient biodegradable and reusable green catalyst for this multicomponent reaction. The chitosan catalyst can be reused 10 times in fresh reaction. Catalytic activity has been sustained in the first five runs but slightly decreased in subsequent cycles.

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

“…[29] Other methods have also been developed within the past three decades. [30] In the past years, a few methods have described the one-pot multicomponent synthesis of quinazolinones based on catalysts such as NH 2 SO 3 H, [31] thiamine hydrochloride, [32] CuCl, [33] chitosan, [34] nafion-H, [35] Mg-Al-CO 3 , [36] silica gel, [37] and H 6 P 2 W 18 O 6 · 18H 2 O [38] from the reaction of aromatic aldehydes, 2-amino benzimidazole/ 3-amino-1,2,4-triazole, and α-hydroxy C-H acids. Nevertheless, these methods may be restricted to benzaldehyde and have some significant limitations, such as harsh reaction conditions, long reaction time, tedious workup, poor yields, and use of metal-and moisture-sensitive catalysts.…”

Chitosan as a Natural Polymer for Heterogeneous Catalysts Support: A Short Review on Its Applications

“…For instances, chitosan was extensively investigated in metal extraction [2][3][4], chemical synthesis reaction [5,6] and electrolyte-based fuel cells studies [7,8]. Chitosan was explored to be a mild and direct solid catalyst in organic synthesis without any post-modification [6,9,10].…”

Agar: a novel, efficient, and biodegradable catalyst for the one-pot three-component and green synthesis of 2,3-dihydroquinazolin-4(1H)-one, 4H-pyrimidobenzothiazole and 2-aminobenzothiazolomethylnaphthol derivatives

“…In particular, natural biopolymers are important candidates to explore for catalysts, and their properties provide the possibility to perform reactions for acid-sensitive substrates, under milder reaction conditions and better selectivity [23][24][25]33].…”