Mechano-Biocatalytic Rapid Synthesis of 2-Amino-3-cyano-4H-pyran Derivatives

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 60 ºC, 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.

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Three-Component Synthesis of Tetrahydrobenzo[b]pyrans Catalyzed by Sodium Cyclamate

Kiyani¹,

Baghaie²

2022

HETEROCYCLES

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The one-pot three-component cyclocondensation for the synthesis of tetrahydrobenzo [b]pyran derivatives in the presence of sodium cyclamate has been investigated. The three-component reaction was carried out in water medium under refluxing condition. Screening the reaction conditions revealed that 20 mol% sodium cyclamate refluxing water afforded the best results. Under green conditions, different substituted tetrahydrobenzo[b]pyrans were obtained from simple available starting materials, including malononitrile, functionalized benzaldehydes, and dimedone, via using an established efficient and straightforward approach.Multicomponent reactions (MCRs) involve at least three reactants that reacted in one-pot approach to synthesize valuable organic compounds and pharmacologically active molecules with high complexity and diversity as well as minimum side reactions. Green bond-forming, atomic and structural economy, step economy, high bond-forming index, avoidance of complicated purification processes and separation of intermediates, time-saving, mild conditions, environmental friendliness, elimination of waste production, energy-saving, and excellent functional group compatibility are the merits of MCRs. 1 In this reason, MCRs have been used for the synthesis of various heterocyclic compounds. 2 Tetrahydrobenzo[b]pyran derivatives are one of the biologically scaffolds owing to their applications in the synthetic and medicinal chemistry. 3 These important oxygen-containing heterocyclic compounds exhibit bioactivities, including anti-coagulant, 3 anti-anaphylactic, 3 calcium antagonist, 3 anticancer, 4 antibacterial, 5 anti-inflammatory, 6 lactamase inhibitor, 7 antifungal, 8 antioxidant, 8 anti-Huntington, anti-Alzheimer, anti-Schizophrenia, and anti-Parkinson. 3,9 The structures of some biologically active tetrahydrobenzo [b]pyrans are depicted in Figure 1. Besides, tetrahydrobenzo[b]pyrans were applied as starting materials to synthesize spirocyclopropylbarbiturates, 10 spirocyclopropylpyrazolones,

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Mechano-Biocatalytic Rapid Synthesis of 2-Amino-3-cyano-4H-pyran Derivatives

Cited by 3 publications

References 20 publications

Six-membered ring systems: With O and/or S atoms

Six-membered ring systems: With O and/or S atoms

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

Three-Component Synthesis of Tetrahydrobenzo[b]pyrans Catalyzed by Sodium Cyclamate

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