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

我们发现了一种新的刘易斯酸，它是有机合成中最常用的刘易斯酸，它是由BF_3-Oet_2配合物和Me_3SiOTf按1：1的比例在乙腈中生成的。新生成的刘易斯酸经~ 1H-NMR、~ 1F-NMR和~ 1B-NMR测定，确定其结构为BF_2（OTf）<19><11>。这些NMR测量结果中最重要的信息是Me_3SiF的检测。分子香料的生成表明，在乙腈中，BF_3-Oet_2配合物与Me_3SiOTf之间发生了快速的金属转移反应，并将这种新的刘易斯酸命名为BF_2（OTF），用于刘易斯酸介导的有机反应。发现这种新的刘易斯酸非常有用。特别是对某些具有自由羟基（无保护基）的甲基吡喃糖衍生物，艾杜糖，葡萄糖和半乳糖，都能有效地进行高度立体控制的C-烯丙基糖苷化反应

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)