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Photochemistry of Isothiocoumarin (= 1H-[2]benzothiopyran-1-one) |
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| Authors: | John Bethke Jürgen Kopf Paul Margaretha Bernard Pignon Léon Dupont Léon E Christiaens |
| Institution: | 1. Institut für Organische Chemie, Universität Hamburg, M. L. King Platz 6, D-20146 Hamburg;2. Institut für Organische Chemie, Universität Hamburg, M. L. King Platz 6, D-20146 Hamburg
Institut fü Anorganishche und Angewandte Chemie, Universität Hamburg.;3. Institut de Chimie Organiqué B6, Université de Liège, Sart-Tilman, B-4000 Liège;4. Institut de Chimie Organiqué B6, Université de Liège, Sart-Tilman, B-4000 Liège Service de Cristallographie, Institut de Physique B5, Univesité de Liège. |
| Abstract: | Irradiation (λ = 350 nm) of 1H-2]benzothiopyran-1-one ( 2 ) in the solid state affords selectively and in good yield 6aα, 6bα, 12bα, 12cα -tetrahydrocyclobuta1, 2-c:4, 3-c′]bis(2]benzothiopyran)-5, 8-dione ( 3 ), the head-to-head (HH) cis-cisoid-cis-cyclodimer of 2 , X-Ray analysis of 2 confirms that this reaction proceeds according to the well-established topochemical principles. The same dimer 3 is obtained in low yields on irradiation of 10?1 M solutions of 2 in either MeOH or MeCN, while no conversion at all is observed in benzene. On irradiation of 2 in MeCN in the presence of tetrachloroethene, the 2 + 2] photocycloadduct 4 is formed in good yield, the conversion 2 → 4 being efficiently quenched by naphthalene. In contrast, no reaction is observed -on irradiation of 2 in the presence of 2, 3-dimethylbut-2-ene, neither in polar nor in apolar solvents. |
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