Solid-state and solution photocycloadditions of 4-acyloxy-2-pyrones with maleimide |
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Authors: | Tetsuro Shimo |
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Institution: | Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan |
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Abstract: | Solid-state photosensitized reactions of 4-acyloxy-2-pyrones (1b,c) with maleimide (2) afforded endo-endo double-4+2] cycloadducts (3b,c) with high stereoselectivity. Sensitized photoreactions of 1a-d with 2 in solution gave exo-endo double-4+2] cycloadducts (4a-d). 2-Pyrones 1a-d were photolyzed to give carboxylic acids (5a-d) via their valence isomerization in the solid state and in solution. Such kinds of photoreaction of the 4-acyloxy-2-pyrones were dramatically different from regio- and stereoselective 2+2] cycloadditions of 4-alkyloxy-2-pyrones. The photoreaction mechanisms of 1 with 2 and 1 itself were analyzed by powder X-ray diffraction analysis and MO calculations. |
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Keywords: | Solid-state photosensitized reaction 2-Pyrones Maleimides [4+2] Cycloadducts |
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