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Rice husk SiO2 (NPs) supported-BO3H3: a highly active, solvent-free and recyclable catalyst to dihydropyrimidin-2(1H)ones-(thiones) and coumarin-3-carboxylic acid synthesis

Khatavi, S Y and Kantharaju, K and Yamanappa, H and Raghothama, S (2019) Rice husk SiO2 (NPs) supported-BO3H3: a highly active, solvent-free and recyclable catalyst to dihydropyrimidin-2(1H)ones-(thiones) and coumarin-3-carboxylic acid synthesis. In: CURRENT SCIENCE, 117 (11). pp. 1828-1841.

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Official URL: https://dx.doi.org/10.18520/cs/v117/i11/1828-1841

Abstract

3,4-Dihydropyrimidin-2(1H)ones(thiones) (DHPM) and coumarin-3-carboxylic acid are obtained in excellent to good yield by employing green catalyst under solvent-free condition. The condensation of substituted arylaldehyde, 1,3-diketoester and urea/thiourea in the presence of green catalyst after 1 h of stirring at 50 degrees C resulted in DHPM. The reaction of substituted o-hydroxybenzaldehyde with Meldrum's acid in the presence of catalyst under sonication for a few minutes gave coumarin-3-carboxylic acid. Here, we have used Lewis acid catalyst RHA-SiO2(NPs)-BO3H3 derived from the agro-waste of rice husk, a heterogeneous catalyst for important organic scaffold synthesis. The reaction required low catalyst loading (1.2 mg) to achieve a target product under solvent-free condition. A series of other derivatives of heterogeneous catalysts synthesized are RHA-SiO2, RHA-SiO2(NPs), RHA-SiO2-BO3H3. We examined their catalytic activity in the synthesis of DHPM and coumarin-3-carboxylic acid. Only the reaction catalysed by RHA-SiO2(NPs)-BO3H3 gave excellent yield of the product. The final isolated pure product has been fully characterized by various spectroscopic methods and confirmed.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to INDIAN ACAD SCIENCES
Keywords: Agro-waste; coumarin-3-carboxylic acid; dihydropyrimidin-2(1H)ones(thiones); heterogeneous catalyst; rice husk
Department/Centre: Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility)
Depositing User: Id for Latest eprints
Date Deposited: 31 Dec 2019 06:02
Last Modified: 31 Dec 2019 06:02
URI: http://eprints.iisc.ac.in/id/eprint/64252

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