Achieving Enantioselectivity in Difficult Cyclohexa-1,3-diene Diels–Alder Reactions with Sulfur-Stabilized Silicon Cations as Lewis Acid Catalysts
作者:Polina Shaykhutdinova、Martin Oestreich
DOI:10.1021/acs.orglett.8b02945
日期:2018.11.16
A novel cationic silicon–sulfur Lewis pair with a chiral H8-binaphthyl backbone is reported. It catalyzes otherwise sluggish Diels–Alderreactions of cyclohexa-1,3-diene and chalcone derivatives in good yields and decent enantioselectivities (up to 81% ee). The enantioinduction is highest with a [1,1′-biphenyl]-4-yl substituent at the carbonyl carbon atom. This moiety can be later converted into a
The first generalpalladium-catalyzedcarbonylative vinylation of aryl halides with olefins in the presence of CO has been developed. Applying a catalyst system consisting of [(cinnamyl)PdCl](2) and bulky imidazolyl-phosphine ligand L1 allows for the efficient and selective synthesis of α,β-unsaturated ketones under mild reaction conditions. Starting from easily available aryl halides and olefins,
在 CO 存在下,第一个通用钯催化的芳基卤化物与烯烃的羰基化乙烯基化已经被开发出来。应用由 [(肉桂基)PdCl](2) 和庞大的咪唑基膦配体 L1 组成的催化剂体系,可以在温和的反应条件下高效和选择性地合成 α,β-不饱和酮。从容易获得的芳基卤化物和烯烃开始,可以以简单的方式制备通用的结构单元。证明了这种新协议的通用性和功能组耐受性。
Continuous-flow hydration–condensation reaction: Synthesis of α,β-unsaturated ketones from alkynes and aldehydes by using a heterogeneous solid acid catalyst
A simple, practical and efficient continuous-flow hydration-condensation protocol was developed for the synthesis of alpha,beta-unsaturated ketones starting from alkynes and aldehydes by employing a heterogeneouscatalyst in a flow microwave. The procedure presents a straightforward and convenient access to valuable differently substituted chalcones and can be applied on multigram scale.
Organoselenium-Catalyzed Asymmetric Cyclopropanations of (<i>E</i>)-Chalcones
作者:Pei-Tung Cheng、Yu-Hsun Tseng、Rong-Jie Chein
DOI:10.1021/acs.orglett.1c03243
日期:2021.10.15
compounds were used to catalyze asymmetriccyclopropanation reactions; the selenonium ylide intermediates formed from these selenium-containing catalysts and benzyl bromide efficiently react with (E)-chalcones to give various cyclopropanes (27 examples) with excellent enantioselectivities of ≤99% ee and are the first examples of organoselenium-catalyzed asymmetriccyclopropanations.
我们报告了一类新的基于 ( S )-二苯基(四氢硒酚-2-基) 甲醇的手性四氢硒酚,其由 ( R )-3-(3-溴丙基)-2,2-二苯基环氧乙烷和硒化钠制备。这些手性四氢硒酚类化合物用于催化不对称环丙烷化反应;由这些含硒催化剂和苄基溴形成的硒叶立德中间体与 ( E )-查耳酮有效反应,得到各种环丙烷(27 个实例),具有≤99% ee 的优异对映选择性,是有机硒催化不对称环丙烷化的第一个实例。