Preparation and regioselective SN2' reaction of novel gem-difluorinated vinyloxiranes with RLi |
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Authors: | Ueki Hisanori Chiba Takashi Yamazaki Takashi Kitazume Tomoya |
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Institution: | Graduated School of Bioscience and Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8510, Japan. |
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Abstract: | A series of hitherto unknown 3,4-epoxy-1,1-difluorobutenes were prepared from the readily accessible alpha,beta-epoxy ketones and these compounds were found to undergo regioselective S(N)2' reactions with hard RLi nucleophiles occurring at the highly positively charged terminal fluorine-possessing sp(2) carbon atom in quite sharp contrast to the cases of the corresponding nonfluorinated vinyloxiranes which only attained a low level of regioselectivity. Addition of HMPA substantially improved the products' olefinic stereoselectivity. Theoretical calculations were used to qualitatively explore the nature of selectivity in these reactions. |
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