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Stabilization and activation of unstable propynal in the zeolite nanospace and its application to addition reactions

Abstract

Propynal (HC≡C−CHO) having both a C≡C triple bond and a formyl group in a molecule is a promising building block, but its labile property to easily polymerize often narrows its application for organic synthesis. In a similar way to unstable molecules, such as formaldehyde and acrolein, propynal is also stabilized and remains unchanged in the supercages of the Na-Y zeolite for over 30 days at ambient temperature, where the carbonyl oxygen atoms of the propynal coordinate to sodium ions in Na-Y which was proved by a 13C-DD/MAS-NMR analysis. In addition, the propynal adsorbed in the zeolite is sufficiently activated to allow unprecedented reactions; i.e., (1) The 1,3-dipolar cycloaddition with electron-deficient α-diazocarbonyl compounds, (2) the 1,4-addition with mono-, di-, and trimethoxy-substituted benzenes, and (3) the [2 + 2] cycloaddition of unactivated cycloalkenes. The nanospace of the zeolites keeps the products from dimerization during reaction (1) and from successive side-reactions in reaction (2). Quantum chemical calculation demonstrated that reaction (3) proceeds via a one-step-like non-concerted mechanism to afford the corresponding [2 + 2] cycloadducts. The three reactions can produce valuable synthetic intermediates retaining both a formyl group and a C=C double bond.

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Publication details

The article was received on 09 Jun 2017, accepted on 07 Aug 2017 and first published on 07 Aug 2017


Article type: Paper
DOI: 10.1039/C7CY01161J
Citation: Catal. Sci. Technol., 2017, Accepted Manuscript
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    Stabilization and activation of unstable propynal in the zeolite nanospace and its application to addition reactions

    D. Hayashi, Y. Igura, Y. Masui and M. Onaka, Catal. Sci. Technol., 2017, Accepted Manuscript , DOI: 10.1039/C7CY01161J

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