Rhodium‐Catalyzed Remote C(sp
<sup>3</sup>
)−H Borylation of Silyl Enol Ethers
作者:Jie Li、Shuanglin Qu、Wanxiang Zhao
DOI:10.1002/anie.201913281
日期:2020.2.3
rhodium-catalyzed remote C(sp3 )-H borylation of silylenolethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional-group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derivedfrom aldehydes and ketones, and provides direct access to a broad range of structurally
chiral boron compounds. This protocol is well suitable for activated alkenes such as vinylarenes and alkenes bearing directing groups. However, the catalytic enantioselective hydroboration of O-substituted alkenes has remained unprecedented. Here we report a Rh-catalyzedenantioselective hydroboration of silyl enol ethers (SEEs) that utilizes two new chiral phosphine ligands we developed. This approach
“<i>Syn-Effect</i>” in the Conversion of (<i>E</i>)-α,β-Unsaturated Esters into the Corresponding β,γ-Unsaturated Esters and Aldehydes into Silyl Enol Ethers
The stereochemistry in the conversion of (E)-α,β-unsaturated esters into the corresponding β,γ-unsaturated esters, and that in the conversion of aldehydes into the silyl enol ethers, were investigated. The Z/E ratios of the resulting β,γ-unsaturated esters and the silyl enol ethers varied according to the γ-substituents of the (E)-α,β-unsaturated esters and the α-substituents of the aldehydes, respectively