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Current Organic Chemistry

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ISSN (Print): 1385-2728
ISSN (Online): 1875-5348

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Research Article

Synthesis of Tetrahydrobenzo[b]pyrans Catalyzed by 1,3-Dibenzyl-1H-benzo[d] imidazole-3-ium Chloride

Author(s): Ali Moradi Delfani, Hamzeh Kiyani* and Mehdi Zamani

Volume 27, Issue 17, 2023

Published on: 18 October, 2023

Page: [1542 - 1552] Pages: 11

DOI: 10.2174/0113852728269951231009060535

Price: $65

Abstract

Tetrahydrobenzo[b]pyrans are fused oxygen-containing heterocycles that are found in many biologically active compounds. Therefore, researchers in organic synthesis are searching for suitable, efficient, and useful methods for their synthesis. In this contribution, a series of tetrahydrobenzo[b]pyran derivatives was synthesized using aryl aldehydes, malononitrile, and cyclohexane-1,3-dione or dimedone as the available starting materials. The three-component reactions were catalyzed by 1,3-dibenzyl-1H-benzo[d]imidazol-3-ium chloride as the N-heterocyclic carbene precursor. The heterocyclic oxygen-containing products were obtained in good to excellent isolated yields within relatively shorter reaction times. Optimizing the reaction conditions was performed from the point of view of various parameters of the reaction. The results of these experiments showed that the best solvent system includes water-ethanol, the most suitable reaction temperature is 60ºC, and the optimal amount of the imidazolium catalyst loading is 5 mol%. Operational simplicity, no need for chromatographic methods for purification, simple work-up for pure products, and avoiding hazardous solvents are remarkable features of this three-component reaction. Moreover, in these multicomponent cyclo-condensations, no by-products were observed.

Keywords: Tetrahydrobenz[b]pyran, malononitrile, 1, 3-dibenzyl-1H-benzo[d]imidazol-3-ium chloride, aqueous media, multi-component synthesis, tandem cyclization.

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