Regio- and stereoselective reactions of gem-difluorinated vinyloxiranes with heteronucleophiles |
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Authors: | Ueki Hisanori Kitazume Tomoya |
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Institution: | Graduate School of Bioscience and Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan. |
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Abstract: | Reaction: see text]. Regio- and stereoselectivity in reactions of gem-difluorinated vinyloxiranes with heteronucleophiles were successfully controlled. Halogen atoms were introduced regioselectively at the allylic epoxide carbon with an inversion in stereochemistry using MgBr2*Et2O or Li2CuCl4 to produce anti-vic-halohydrine. The other diastereomers were obtained selectively using LiBr/AcOH or BCl3, and SN2' type products were formed selectively with excellent E preference by changing the reaction temperature. Moreover, a further investigation led us to find that a regio- and stereoselective SN2' addition of several Brnsted acids was dependent on the pKa values of the acids. Under strong acidic conditions, we exclusively obtained E allylic alcohols. |
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