权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Route for Optically Active Cyclopropanols Utilizing Organoboranes

利用有机硼烷制备光学活性环丙醇的路线

基本信息

批准号：
02640374
负责人：
IMAI Toshiro
金额：
$ 1.34万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Terminal alkenylboronic acids were easily es. terified with tartaric esters or amides. The chirally modified boronic esters were then cyclopropanated by the Simmons-Smith procedure with high "diastereoface differentiation. Thus produced cyclopropylboronate derivatives could then be oxidized under mild conditions to the corresponding optically active cyclopropanols. Internal alkenylboronic esters, on the other hand, could not be cyclopropanated smoothly by the Simmons-Smith reaction and some other carbenoid reactions. By these results, it was suggested that the a-alkyl substituent of these alkenyboronic esters might cause steric interference in the transition state geometry. The optically active 'cyclopropanols-obtained above were converted to the ringopened products without touching the asymmetric carbon center at the beta position by first converting to its silyl ether and then subjecting to the acetoxymercuration-demercuration reaction. Furthermore, the optically active cyclopropylboronate intermediates can be converted to various types of synthetically useful compounds not only by the oxidation reaction but also by variety of known reactions of organoboranes. To demonstrate it, here, the onecarbon hbmologation reaction with chlbromethyl-lithium was applied. This reaction followed by oxidative work-up afforded the corresponding optically active cyclopropylmethanol derivatives. These compouids have, previously, been shown to be convertible to threo-2-methyl-1, 3-alkanediols by the oxymercuration-demercuration reaction which proceeds regioselective and stereospecific manner. Therefore, this asymmetric cyclopropanation reaction of alkenylboronic ester derivatives provides optically active cyclopropanols and cyclopropylmethanols of high synthetic potential.

端烯基硼酸易为ES。用酒石酸酯或酰胺表示的。手性修饰的硼酸酯随后通过Simmons-Smith过程进行环丙烷化，具有高的“非对映界面分化”。这样生成的环丙基硼酸衍生物可以在温和的条件下被氧化成相应的光学活性环丙醇。另一方面，通过Simmons-Smith反应和其他类卡宾反应，内烯基硼酸酯不能顺利地环丙烷化。根据这些结果，推测这些烯基硼酸酯的α-烷基取代基可能在过渡态几何构型中引起空间位阻。上述光学活性的‘环丙醇’在不接触β位置的不对称碳中心的情况下，通过首先转化为其硅醚，然后进行乙酰氧汞-脱汞反应，转化为开环产物。此外，光学活性的环丙基硼酸酯中间体不仅可以通过氧化反应转化为各种合成有用的化合物，还可以通过有机硼烷的各种已知反应转化为各种合成有用的化合物。为了证明这一点，这里应用了一碳与氯甲基锂的氢化反应。该反应后的氧化反应得到了相应的光学活性环丙基甲醇衍生物。这些化合物以前已经被证明可以通过氧化汞-脱硫基反应转化为苏-2-甲基-1，3-烷基二醇，该反应进行区域选择性和立体专一性。因此，这种烯基硼酸酯衍生物的不对称环丙烷化反应提供了具有光学活性的环丙醇和环丙基甲醇，具有很高的合成潜力。