Blair Daniel J, Tanini Damiano, Bateman Joseph M, Scott Helen K, Myers Eddie L, Aggarwal Varinder K
School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK . Email:
Chem Sci. 2017 Apr 1;8(4):2898-2903. doi: 10.1039/c6sc05338f. Epub 2017 Feb 9.
Diborylmethane can be homologated uni- and bidirectionally by using enantiomerically pure lithium-stabilized carbenoids to give 1,2- and 1,3-bis(boronic esters), respectively, in good yield and with excellent levels of enantio- and diastereoselectivity. The high sensitivity of the transformation to steric hindrance enables the exclusive operation of either manifold, effected through the judicious choice of the type of carbenoid, which can be a sparteine-ligated or a diamine-free lithiated benzoate/carbamate. The scope of the 1,2-bis(boronic esters) so generated is complementary to that encompassed by the asymmetric diboration of alkenes, in that primary-secondary and primary-tertiary 1,2-bis(boronic esters) can be prepared with equally high levels of selectivity and that functional groups, such as terminal alkynes and alkenes, are tolerated. Methods for forming -symmetric and non-symmetrical and 1,3-bis(boronic esters) are also described and represent a powerful route towards 1,3-functionalized synthetic intermediates.
通过使用对映体纯的锂稳定类卡宾，可以对二硼甲烷进行单向和双向同系化反应，分别以良好的产率以及优异的对映选择性和非对映选择性得到1,2 - 和1,3 - 双（硼酸酯）。该转化反应对空间位阻的高敏感性使得通过明智地选择类卡宾的类型（可以是司巴丁连接的或无二胺的锂化苯甲酸酯/氨基甲酸酯），能够单独进行任一同系化反应路径。如此生成的1,2 - 双（硼酸酯）的范围与烯烃不对称双硼化反应所涵盖的范围互补，因为可以以同样高的选择性制备伯 - 仲和伯 - 叔1,2 - 双（硼酸酯），并且可以耐受诸如末端炔烃和烯烃等官能团。还描述了形成对称和非对称1,3 - 双（硼酸酯）的方法，这些方法是通往1,3 - 官能化合成中间体的有效途径。
