Double Diastereoselective Approach to Chiral syn- and anti-1,3-Diol Analogues through Consecutive Catalytic Asymmetric Borylations
Double Diastereoselective Approach to Chiral syn- and anti-1,3-Diol Analogues through Consecutive Catalytic Asymmetric Borylations
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DOI：
10.1021/acs.joc.7b00854
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发表时间：
2017-07-21
影响因子：
3.6
通讯作者：
Whiting, Andrew
中科院分区：
文献类型：
--
作者：
Pujol, Alba;Whiting, Andrew
通过亚胺化、β-硼基化、亚胺水解和Wittig捕获序列从不饱和醛衍生的高烯丙基硼酸酯羧酸酯进行第二次硼基加成，得到1，3-二硼基化羧酸酯。通过以下方法实现了对两个新的1，3-立体中心的绝对和相对立体化学的控制：（1）直接手性催化剂控制高e.e.不饱和亚胺上第一个立体中心的不对称硼基化;和（2）不饱和酯的双重非对映选择性控制的硼基化，其使用手性催化剂以在很大程度上克服来自第一手性硼基中心的定向效应，从而得到差的（错配的）到好的（匹配的）非对映控制。随后，这两个C-B功能被转化为C-O系统，以允许明确的立体化学分配的两个硼基化反应，涉及氧化和缩醛形成。
Homoallylic boronate carboxylate esters derived from unsaturated aldehydes via an imination, beta-borylation, imine hydrolysis, and Wittig trapping sequence, were subjected to a second boryl addition to give 1,3-diborylated carboxylate esters. Control of the absolute and relative stereochemistry of the two new 1,3-stereogenic centers was achieved through: (1) direct chiral catalyst controlled asymmetric borylation of the first stereocenter on the unsaturated imine with high e.e.; and (2) a double diastereoselectively controlled borylation of an unsaturated ester employing a chiral catalyst to largely overcome directing effects from the first chiral boryl center to give poor (mismatched) to good (matched) diastereocontrol. Subsequently, the two C-B functions were transformed into C-O systems to allow unambiguous stereochemical assignment of the two borylation reactions involving oxidation and acetal formation.