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Issue 17, 2012
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Photochemical-mediated solid-state [2+2]-cycloaddition reactions of an unsymmetrical dibenzylidene acetone (monothiophos-dba)

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Abstract

A novel unsymmetrical dibenzylidene acetone (monothiophos-dba, compound 3), containing two chemically different alkene moieties, undergoes a selective photochemically-induced [2+2] cycloaddition solid-state transformation (single crystal and powder), as shown by X-ray diffraction methods. In the single crystal the rate constant for the cycloaddition reaction was determined {k = (2.3 ± 0.1) × 10−4 s−1}, with a 69% conversion attained, which compares well with a two-photon irradiation experiment using a Nd:YAG laser pumped dye laser at 605 nm radiation (66% conversion). Full conversion was attained using powdered 3 after 43 h. A similar conversion was noted between the single crystal and powder forms (59% and 66% conversion after 5 h irradiation). Irradiation of monothiophos-dba in solution using a 325 nm laser, and monitoring by 1H NMR spectroscopy, showed that no cycloaddition occurred, but exclusive photochemically-induced transcis isomerisation of the alkene bond connecting the unsubstituted aryl group (cistrans isomerisation in these electron-deficient and polarised C[double bond, length as m-dash]C bonds occurs rapidly by thermal equilibration).

Graphical abstract: Photochemical-mediated solid-state [2+2]-cycloaddition reactions of an unsymmetrical dibenzylidene acetone (monothiophos-dba)

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Publication details

The article was received on 02 Apr 2012, accepted on 13 Jun 2012 and first published on 14 Jun 2012


Article type: Paper
DOI: 10.1039/C2CE25480H
CrystEngComm, 2012,14, 5564-5571

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    Photochemical-mediated solid-state [2+2]-cycloaddition reactions of an unsymmetrical dibenzylidene acetone (monothiophos-dba)

    A. G. Jarvis, H. A. Sparkes, S. E. Tallentire, L. E. Hatcher, M. R. Warren, P. R. Raithby, D. R. Allan, A. C. Whitwood, M. C. R. Cockett, S. B. Duckett, J. L. Clark and I. J. S. Fairlamb, CrystEngComm, 2012, 14, 5564
    DOI: 10.1039/C2CE25480H

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