DEVELOPMENT OF THE NEW ORGANIC REACTION BY USING NEW LEWIS ACID, BF_2(Otf)

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We found a new Lewis acid which were easily generated from BF_3-Oet_2 complex and Me_3SiOTf in 1:1 ratio, as the most general and popular Lewis acid in organic synthesis, in acetonitrile. Structure of the newly generated Lewis acid were determined as BF_2(Otf) by measurement of ^1H-NMR, ^<19>F-NMR abd ^<11>B-NMR. The most important information from those NMR measurement results was detection of the Me_3SiF. Generation of the molecular spices indicates that transmetalation reaction take place quickly between BF_3-Oet_2 complex and Me_3SiOTf in acetonitrile.This newly developed Lewis acid, as BF_2(Otf), was examined toward some Lewis acid mediated organic reactions. It found that this new Lewis acid was very useful. Especially, highly stereocontrolled C-allylglycosidation reaction efficiently took place toward some kinds of methyl pyranose derivatives, idose, glucose and galactose, with free hydroxyl groups (no protecting groups)