新型偕二氟代乙烯基环氧乙烷与RLi的制备及区域选择性SN2'反应

Preparation and regioselective SN2' reaction of novel gem-difluorinated vinyloxiranes with RLi.

作者信息

Ueki Hisanori, Chiba Takashi, Yamazaki Takashi, Kitazume Tomoya

机构信息

Graduated School of Bioscience and Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8510, Japan.

出版信息

J Org Chem. 2004 Oct 29;69(22):7616-27. doi: 10.1021/jo049025x.

DOI:10.1021/jo049025x

PMID:15497989

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.

摘要

一系列迄今未知的3,4-环氧-1,1-二氟丁烯由易于获得的α,β-环氧酮制备而成，并且发现这些化合物与硬RLi亲核试剂发生区域选择性S(N)2'反应，反应发生在带高度正电荷的、带有氟原子的末端sp(2)碳原子上，这与相应的非氟化乙烯基环氧乙烷的情况形成鲜明对比，后者仅具有较低水平的区域选择性。加入HMPA可显著提高产物的烯烃立体选择性。理论计算用于定性探究这些反应中选择性的本质。