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Tri-lacunary polyoxometalates of Na8H[PW9O34] as heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation and the synthesis of benzoxazole derivatives

Paper ID Volume ID Publish Year Pages File Format Full-Text
39827 45837 2014 7 PDF Available
Title
Tri-lacunary polyoxometalates of Na8H[PW9O34] as heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation and the synthesis of benzoxazole derivatives
Abstract

•The POMs of Na8H[PW9O34] have been developed as heterogeneous catalysts.•The POMs catalysts can catalyze the reactions selectively and efficiently.•The POMs catalysts can catalyze the reactions at 25 °C under mild conditions.•The POMs catalysts can catalyze the reactions in chloride-free solvents.

We reported for the first time the development of tri-lacunary polyoxometalates (POMs) of Na8H[A-PW9O34]·7H2O and Na8H[B-PW9O34]·19H2O (Na-A-PW9 and Na-B-PW9) as highly selective and efficient heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation of various aldehydes and ketones and the synthesis of benzoxazole derivatives at 25 °C under mild conditions. Since both Na-A-PW9 and Na-B-PW9 display no characteristic porosity, it is proposed that the catalytic reactions proceed not only on the surface and interface, but also in the bulk phase. The catalysts can be easily recovered and reused for at least six times without obvious decrease of catalytic activities and the structures of the catalysts remain unchanged after recycling. The easy preparation, high efficiency, reusability of the heterogeneous catalysts of Na-A-PW9 and Na-B-PW9 exhibit great potential for further application.

Graphical abstractWe reported for the first time the development of tri-lacunary polyoxometalates (POMs) of Na8H[A-PW9O34]·7H2O and Na8H[B-PW9O34]·19H2O (Na-A-PW9 and Na-B-PW9) as highly selective and efficient heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation of various aldehydes and ketones and the synthesis of benzoxazole derivatives at 25 (C under mild conditions. Since both Na-A-PW9 and Na-B-PW9 display no characteristic porosity, it is proposed that the catalytic reactions proceed not only on the surface and interface, but also in the bulk phase. The catalysts can be easily recovered and reused for at least six times without obvious decrease of catalytic activities and the structures of the catalysts remain unchanged after recycling. The heterogeneous catalysts of Na-A-PW9 and Na-B-PW9 exhibit great potential for further application.Figure optionsDownload full-size imageDownload high-quality image (88 K)Download as PowerPoint slide

Keywords
Polyoxometalates; Lanthanides; Cyanosilylation; Lewis acids
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Tri-lacunary polyoxometalates of Na8H[PW9O34] as heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation and the synthesis of benzoxazole derivatives
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 475, 5 April 2014, Pages 140–146
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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Price after discount Only $4.95
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