NHC-catalyzed enantioselective C2-functionalization of 3-hydroxychromenones <i>via</i> α,β-unsaturated acyl azoliums
作者:Krzysztof Dzieszkowski、Michał Słotwiński、Katarzyna Rafińska、Tadeusz M. Muzioł、Zbigniew Rafiński
DOI:10.1039/d1cc03708k
日期:——
A novel synthetic method for enantioselective C2-functionalization of 3-hydroxychromenones promoted by N-heterocyclic carbenes via the formation of α,β-unsaturatedacylazolium intermediates, which occurs with Coates–Claisen rearrangement is established. This synthetic strategy enabled the rapid assembly of enantiomerically enriched δ-hydroxychromenone-derived esters/amides under mild conditions with
Asymmetric Conjugate Addition of 3‐Hydroxychromen‐4‐Ones to Electron‐Deficient Olefins Catalyzed by Recyclable C
<sub>2</sub>
‐Symmetric Squaramide
作者:Ruslan A. Kovalevsky、Alexander S. Kucherenko、Alexander A. Korlyukov、Sergei G. Zlotin
DOI:10.1002/adsc.202101019
日期:2022.1.18
The readily scalable asymmetricsynthesis of the chiral chromone derivatives functionalized at position 2 via electrophilic enantioselective olefination of the chromone core with nitroolefins and ß,γ-unsaturated α-ketoesters in the presence of simple C2-symmetric tertiary amine-squaramide catalyst was developed. The reaction products were obtained in 80–99% yield with 89–99% ee in 95% EtOH. The absolute
在简单的 C 2 -对称叔胺-方酸酰胺催化剂存在下,通过色酮核心与硝基烯烃和β , γ -不饱和α -酮酯的亲电对映选择性烯化,在位置 2 官能化的手性色酮衍生物的易于扩展的不对称合成被开发出来。反应产物 在 95% EtOH 中的产率为 80-99%, ee为 89-99%。通过将化合物 ( R ) -3aa转化为已知的甲基 ( R ) -β-硝基-α,明确确定了合成色酮衍生物的绝对构型-苯丙酸和通过单晶XRD分析化合物( R , S ) -5 aa和( R , S ) -5 ab。难溶于普通有机溶剂的催化剂V可以很容易地从反应混合物中分离出来并重复使用多达 10 个催化循环。对合成的化合物进行催化氢化和酯化反应,以证明所开发过程的合成潜力。
A Direct Organocatalytic Enantioselective Route to Functionalized
<i>trans</i>
‐Diels–Alder Products Having the Norcarane Scaffold
作者:Casper L. Barløse、Niklas L. Østergaard、René S. Bitsch、Marc V. Iversen、Karl Anker Jørgensen
DOI:10.1002/anie.202106598
日期:2021.8.9
organocatalysis with excellent selectivity, high yield and up to five contiguous stereocenters is presented. The reaction concept integrates the halogen effect and a novel discovered pseudo-halogen effect to direct an endo-selective, secondary-amine catalyzed Diels–Alder reaction allowing for the subsequent formation of trans-Diels–Alder cycloadducts featuring the norcarene scaffold. The methodology relies on
Organocatalytic tandem enantioselective Michael-cyclization of isatin-derived β,γ-unsaturated α-ketoesters with 3-hydroxy-4H-chromen-4-one or 2-hydroxy-1,4-naphthoquinone derivatives
作者:Shao-Jie Yin、Shao-Yun Zhang、Jun-Qi Zhang、Bing-Bing Sun、Wei-Tai Fan、Bing Wu、Xing-Wang Wang
DOI:10.1039/c6ra17400k
日期:——
The enantioselective formal [3 + 3] annulation reaction of isatin-derived β,γ-unsaturatedα-ketoesters with 3-hydroxy-4H-chromen-4-ones or 2-hydroxy-1,4-naphthoquinone was successfully implemented under catalysis of quinine-derived bifunctional tertiary amine-thiourea catalysts. The efficienttandem Michael-cyclization has provided facile access to optically active spiro[oxindole-pyrano[3,2-b]chromenone]
在催化作用下,成功地实现了由靛红衍生的β,γ-不饱和α-酮酸酯与3-羟基-4 H-铬烯-4-酮或2-羟基-1,4-萘醌的对映选择性形式[3 + 3]环化反应奎宁衍生的双官能叔胺-硫脲催化剂。高效的串联Michael环化提供了高收率的旋光性[oxindole-pyrano [3,2- b ] chromenone]和spiro [oxindole-benzo [ g ] chromene-dione]衍生物的简便获得方法,具有出色的非对映选择性和对映选择性。