Les reactions de transposition photochimique en serie heterocyclique—IV: Photo-isomerisation des phenyl-methyl thiazoles et isothiazoles isomeres |
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Authors: | C Riou JC Poite G Vernin J Metzger |
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Institution: | Laboratoire de Chimie Organique A, Associé au CNRS, L.A. 126, Université de Droit ol''Economie et des Sciences d''Aix Marseille, Centre de St-Jérôme, 13013 Marseille, France |
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Abstract: | The photochemical behaviour of twelve phenylmethylthiazole isomers is identical to that of non-methylated products. Thus, in order of decreasing reactivity we have: 2-phenylthiazole or 5-phenylisothiazole > 5-phenylthiazole or 3-phenylisothiazole > 4-phenylthiazole or 4-phenylisothiazole. The two latter undergo photoisomerization only to a slight extent.Most of the rearranged compounds (95%) are formed either by a valence bond isomerization mechanism via bicyclic intermediates where the phenyl group is conjugated to the cycle, or by the Kellogg mechanism, through a 180° rotation around the bonds adjacent to the sulphur atom.These results have furthermore allowed us to confirm the selective action of iodine in these isomerization reactions. |
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