A convergent method for the stereoselective synthesis of trisubstituted alkenes
摘要:
A method for the stereoselective, convergent synthesis of trisubstituted alkenes has been developed. The procedure features the synthesis of allylic alcohols 9 by coupling an aldehyde with a vinyl organometallic reagent. Treatment of 9 with carbon disulfide and methyl iodide gave the intermediate allylic xanthates 10 that underwent facile [3,3]-sigmatropic rearrangement to give the dithiocarbonates 11 and 12, radical reduction of which gave the (E)-alkenes 13 as the major products.
Electron-Deficient Olefin Ligands Enable Generation of Quaternary Carbons by Ni-Catalyzed Cross-Coupling
作者:Chung-Yang (Dennis) Huang、Abigail G. Doyle
DOI:10.1021/jacs.5b02503
日期:2015.5.6
A Ni-catalyzed Negishi cross-coupling with 1,1-disubstituted styrenyl aziridines has been developed. This method delivers valuable β-substituted phenethylamines via a challenging reductive elimination that affords a quaternary carbon. A novel electron-deficient olefin ligand, Fro-DO, proved crucial for achieving high rates and chemoselectivity for C-C bond formation over β-H elimination. This ligand
Triazolylidene Iridium Complexes for Highly Efficient and Versatile Transfer Hydrogenation of C═O, C═N, and C═C Bonds and for Acceptorless Alcohol Oxidation
oxidation. High-valent iridium(III) complexes were identified as the most active precursors for the oxidative alcohol dehydrogenation, while a low-valent iridium(I) complex with a methyl ether functionality was most active in reductive transfer hydrogenation. This catalyst precursor is highly versatile and efficiently hydrogenates ketones, aldehydes, imines, allylic alcohols, and most notably also unpolarized
据报道,一组铱(I)和铱(III)配合物带有三唑基亚烷基配体,这些配体包含苯并恶唑,噻唑和甲基醚侧基作为潜在的螯合供体位点。这些基团的键合模式通过NMR光谱和X射线结构分析来鉴定。在转移氢化和无受体醇氧化中,将该配合物评价为催化剂前体。高价铱(III)配合物被确定为氧化醇脱氢最活跃的前体,而具有甲基醚官能团的低价铱(I)配合物在还原转移氢化中最活跃。这种催化剂的前体用途广泛,可以有效地氢化酮,醛,亚胺,烯丙基醇,尤其是非极化烯烃,转移加氢反应非常困难的基质。周转频率高达260小时记录了–1的烯烃氢化反应,而氢转移到酮和醛中的最大周转频率大于2000 h –1。结合同位素标记实验,动力学同位素效应测量和Hammett参数相关性进行的机械研究表明,限制转移的步骤是转移氢化过程中金属从氢化物向基质的氢化物转移,而在醇脱氢中,限制步骤是基质协调到金属中心。
Cobalt-Catalyzed Asymmetric Hydrogenation of 1,1-Diarylethenes
作者:Jianhui Chen、Chenhui Chen、Chonglei Ji、Zhan Lu
DOI:10.1021/acs.orglett.6b00453
日期:2016.4.1
Highlyenantioselective cobalt-catalyzed hydrogenation of 1,1-diarylethenes was developed by using bench-stable chiral oxazoline iminopyridine–cobalt complexes as precatalysts. A unique o-chloride effect was observed to achieve high enantioselectivity. Easy removal as well as further transformations of the chloro group make this protocol a potentially useful alternative to synthesize various chiral
Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes
作者:Yong‐Liang Su、Kuiyong Dong、Haifeng Zheng、Michael P. Doyle
DOI:10.1002/anie.202105472
日期:2021.8.16
pyrazolines from α-diazo compounds and conjugated alkenes is reported. The direct hydrogen atom transfer (HAT) process of α-diazo compounds promoted by the tert-butylperoxy radical generates electrophilic diazomethyl radicals, thereby reversing the reactivity of the carbon atom attached with the diazo group. The regiocontrolled addition of diazomethyl radicals to carbon-carbon double bonds followed by intramolecular
A Phosphite-Pyridine/Iridium Complex Library as Highly Selective Catalysts for the Hydrogenation of Minimally Functionalized Olefins
作者:Javier Mazuela、Oscar Pàmies、Montserrat Diéguez
DOI:10.1002/adsc.201201017
日期:2013.9.16
library of readily available phosphite‐pyridine ligands has been successfully applied for the first time in the iridium‐catalyzed asymmetric hydrogenation of a broad range of minimallyfunctionalizedolefins. The modular ligand design has been shown to be crucial in finding highly selective catalytic systems for each substrate. Excellent enantioselectivities (ees up to 99%) have therefore been obtained