Enantioselective Total Syntheses of (−)-Taiwaniaquinone H and (−)-Taiwaniaquinol B by Iridium-Catalyzed Borylation and Palladium-Catalyzed Asymmetric α-Arylation
作者:Xuebin Liao、Levi M. Stanley、John F. Hartwig
DOI:10.1021/ja110215b
日期:2011.2.23
We report a concise, enantioselective total synthesis of (-)-taiwaniaquinone H and the first enantioselective total synthesis of (-)-taiwaniaquinol B by a route that includes asymmetric palladium-catalyzed α-arylation of a ketone with an aryl bromide that was generated by sterically controlled halogenation via iridium-catalyzed C-H borylation. This asymmetric α-arylation creates the benzylic quaternary
我们报告了 (-)-台湾醌 H 的简明对映选择性全合成,以及 (-)-台湾醌醇 B 的第一个对映选择性全合成,其路线包括用生成的芳基溴对酮进行不对称钯催化 α-芳基化通过铱催化的 CH 硼化反应进行空间控制卤化。这种不对称 α-芳基化产生了台湾醌类中存在的苄基四元立体中心。通过开发路易斯酸促进的级联来构建许多台湾醌类化合物合成中常见的中间体的[6,5,6]三环核心,有效地完成了合成。通过这些化合物的制备,我们证明了通过不对称α-芳基化构建苄基四级立体中心的实用性,即使是那些在α-位缺乏羰基的中心。
The total synthesis of (+)-nootkatone and (−)-7-epi-nootkatone
ketones was facilitated by the action of H2O2 under operationally simple and environmentally benign reaction conditions. The process was highly regioselective and enables stereospecific construction of contiguous quaternary all‐carbon centers from stereodefined all‐substituted all‐cyclic ketones. The asymmetric syntheses of (+)‐cuparene and (+)‐tochuinyl acetate were also successively achieved by taking advantage
在操作简单和环境友好的反应条件下,H 2 O 2的作用促进了环状α-甲酰基酮的氧化环收缩。该过程具有高度的区域选择性,并能够从立体定义的全取代的全环酮立体构筑连续的季碳全碳中心。利用该新方案还成功实现了(+)-cuparene和(+)-tochuinyl乙酸酯的不对称合成。
A novel CAN-SiO2-mediated one-pot oxidation of 1-keto-1,2,3,4-tetrahydrocarbazoles to carbazoloquinones: Efficient syntheses of murrayaquinone A and koeniginequinone A
作者:Suchandra Chakraborty、Gautam Chattopadhyay、Chandan Saha
DOI:10.1002/jhet.561
日期:2011.3
1‐keto‐1,2,3,4‐tetrahydrocarbazoles (1) to carbazole‐1,4‐quinones (2) are efficiently carried out by CAN‐SiO2‐mediated reaction. This generalized protocol was successfully extended to the synthesis of two naturally occurring carbazoloquinones: murrayaquinone A (2b) and koeniginequinone A (2g). A plausible mechanism for this novel reaction involves formation of a 9‐hydroxy‐2,3,4,9‐tetrahydro‐1H‐carbazole‐1‐one
An efficient cationic cyclization reaction has been developed to prepare substituted naphthalenes. The method has been used to prepare a phenanthrene and will be useful for the synthesis of polynucleararomatichydrocarbons and C-glycosyl anthraquinones.