Skeletal Transformation Triggered by C?F Bond Activation after Photochemical Rearrangement of Fluorinated [7]Helicenes |
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Authors: | Chikako Matsuda Ryo Igarashi Prof?Dr Hiroshi Katagiri Dr Takashi Murase |
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Institution: | 1. Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, Yamagata, 990-8560 Japan;2. Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata, 992-8510 Japan |
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Abstract: | Tri- and tetra-fluorinated 7]helicenes are photolabile and undergo a double fluorine atom transfer. Herein, we show that the transferred product further undergoes a skeletal transformation on silica gel. The transformation begins with activation of the allylic C?F bond on the silanol surface. Then, the resulting carbocation readily undergoes a regioselective nucleophilic aromatic substitution with water, depending on the position of the fluorine substituents. Hexafluoro-2-propanol also activated the allylic C?F bond and acted as a nucleophile. These findings support the generation of a highly reactive cationic electrophilic intermediate in the successive transformations involving fluorine atoms. |
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Keywords: | aromatic substitution carbocations C?F bond activation domino reactions fluorine |
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