镍促进电化学还原交叉偶联合成偕二氟烯烃（英文）

偕二氟烯烃是一类重要的含氟有机化合物,在有机合成化学和药物化学研究领域展现出独特的结构优势.例如,偕二氟烯基可以便利地转化为单氟烯基、二氟烷基、三氟甲基以及其他多种含氟结构.偕二氟烯基结构作为羰基理想的电子等排体在药物设计研究中也有广泛的应用.报道了一种镍促进的电化学还原交叉偶联反应合成功能化的偕二氟烯烃.该反应在非分隔电解槽中进行,在温和的电化学还原条件下,实现了三氟甲基烯烃烯丙基脱氟、氧化还原活性羧酸酯脱羧或者烷基卤化物脱卤素的有机结合.反应可有效避免使用化学计量的金属粉末或有机还原剂.该反应为含偕二氟烯基功能结构的生物活性分子提供了有效的合成途径.     

可见光/路易斯碱协同催化的三氟甲基取代烯烃脱氟硅化反应研究

以三氟甲基取代烯烃为底物,使用硅硼烷为硅自由基供体,开发了一项可见光/路易斯碱协同催化的脱氟硅化反应新技术,实现了多样性偕二氟烯丙基硅砌块的绿色高效合成.新反应以奎宁环为路易斯碱催化剂,通过其对硅硼键的辅助活化促进硅自由基生成,表现出绿色温和、体系简单、易于放大、底物适用范围广和官能团兼容性强等优势.此外,本研究还初步展示了该类合成砌块在多类型含偕二氟甲基结构单元构建中的应用.     

二硼二氯甲烷作为通用试剂化学发散性构建偕二硼烷

<正>有机硼化合物是一类高效的合成砌块,在合成化学中应用广泛[1].其中,偕二硼烷类化合物由于其广泛的反应性,引起了极大的研究兴趣,已逐渐成为构建含多种官能团的复杂分子最通用的合成工具之一[2].在过去的二十几年里,化学家们一直致力于开发新方法用于高效构建偕二硼烷类化合物.其中,含官能团底物(如重氮、炔烃、烯烃、偕二卤和羰基化合物等)的直接偕二硼化反应是制备偕二硼烷类化合物最常见的方法之一(Scheme1,PathA)[3];然而,这些方法在制备大位阻的非末端偕二硼烷时往往效率较低,且缺乏通用性[4].     

各种烯基锆化合物的合成及其在立体选择性合成二(三)取代的烯烃中的应用

烯基锆化合物及硒基烯基锆化合物、锡基烯基锆化合物、磺酰基烯基锆化合物、亚磺酰基烯基锆化合物、硅基烯基锆化合物等金属或杂原子取代的烯基锆化合物 ,可通过锆氢化反应高产率和高选择性地制得 .这些试剂可与各种亲电试剂反应立体选择性地合成二取代或三取代的烯烃化合物     

(烷基环戊二烯基)环戊二烯基二氯化钛的合成与反应

Richard在1959年合成了第一个环戊二烯基(取代环戊二烯基)钛衍生物,(CH₃C₅H₄)(C₅H₅)T1Cl₂^[1].我们曾报道了环戊二烯基(烯烃基环戊二烯基)二卤化钛的合成和反应^[2]。     

镍催化氟代烯基硼酯与烷基卤化物Suzuki偶联反应

有机化合物特定位点嵌入氟原子或含氟片段,可以产生独特的生物或物理性质改变.单氟取代烯基是生物医药领域理想的酰胺键替代物,在医药化学、药物研发等方向已经获得广泛的应用.通过溴化镍（Ⅱ）二乙二醇二甲醚复合物、4,4'-二叔丁基-2,2'-二吡啶的催化体系,实现了多种氟代烯基硼酯与一级烷基卤化物碘代物、溴代物以及二级烷基溴代物的Suzuki偶联反应.该反应具有良好的收率和优秀的官能团兼容性,能够兼容酯基、氰基、醇羟基等多种具有有机合成化学价值的官能团,为单氟取代烯烃的合成提供了方法.机理实验表明该反应可能经历烷基卤化物自由基均裂历程.     

基于羧酸作为酰基源的有机偕二硼化合物双官能化转化

正Angew.Chem.Int.Ed.2018,57,5501～5505有机偕二硼化合物由于具有选择性地进行单官能团以及双官能团化的潜力而受到越来越多的关注.然而,目前有机偕二硼化合物的选择性双官能团化依旧具有许多挑战.当有机偕二硼中的一个C—B键进行官能化之后,第二个C—B键的反应活性往往会降低.但是,将偕二硼中的一个C—B键首先接入酰基能够以形成烯醇硼的形式直接活化第二个C—B键,从而实现有机偕二硼的双官能化.中国科学院兰州化学物理研究所苏州研究院/羰基合成与选择     

铁催化酮羰基的硼化反应合成α-羟基硼酸酯

报道了一种铁催化烷基酮类化合物硼化合成三级α-羟基硼酸酯的反应,使用了可商业购买的FeBr₂作为催化剂,加入醇作为添加剂来加速反应的进行,同时避免副反应的发生.通过该方法合成了一系列三级α-羟基硼酸酯化合物,反应具有很好的底物兼容性以及官能团兼容性.该铁催化剂对于大位阻的酮类化合物的硼化反应,表现出优于铜催化的活性.同时该反应可应用于克级规模的制备,随后通过对三级α-羟基硼酸酯的C-O键进行官能化,将所得的三级α-羟基硼酸酯转化为三级烷基硼酸酯以及偕二硼、偕硅硼类化合物.     

钯催化的烯烃异构化反应

烯烃异构反应可以从简单烯烃出发,通过对碳碳双键立体选择性或者位置选择性调控,实现内烯烃化合物尤其其他方法难以构建的多取代烯烃的高效合成,原子经济性高.详细介绍了钯催化烯烃异构化反应的反应机制,系统总结了钯催化的烯烃顺反异构和位置选择性异构反应,以及其在药物分子和天然产物合成中的应用.     

铁催化酮羰基的硼化反应合成α-羟基硼酸酯（英文）

报道了一种铁催化烷基酮类化合物硼化合成三级α-羟基硼酸酯的反应,使用了可商业购买的FeBr_2作为催化剂,加入醇作为添加剂来加速反应的进行,同时避免副反应的发生.通过该方法合成了一系列三级α-羟基硼酸酯化合物,反应具有很好的底物兼容性以及官能团兼容性.该铁催化剂对于大位阻的酮类化合物的硼化反应,表现出优于铜催化的活性.同时该反应可应用于克级规模的制备,随后通过对三级α-羟基硼酸酯的C—O键进行官能化,将所得的三级α-羟基硼酸酯转化为三级烷基硼酸酯以及偕二硼、偕硅硼类化合物.     

Synthesis of glyco-1-ynitols via 1,1-dibromo-1-alkenes from partially and unprotected aldoses

We report the synthesis of 1,1-dibromo-1-alkenes from partially and unprotected aldoses and the synthesis of glyco-1-ynitols from these dibromocompounds. The 1,1-dibromo-1-alkenes were obtained by the reaction of dibromomethyl-triphenylphosphonium bromide in the presence of zinc in refluxing 1,4-dioxane. As an example, when the reaction is performed on 2-deoxy-5-O-trityl-d-ribofuranose (1) the corresponding 1,1-dibromo-1-olefin, (2R,3S)-6,6-dibromo-1-O-trityl-hex-5-ene-1,2,3-triol (12), is obtained in 89% yield. These smooth reaction conditions led also to the achievement of the other olefins from other sugars with good yields (44-90%). The reaction of these olefins with n-butyllithium in THF at low temperature afforded the corresponding alkynes. So the reaction of (2R,3S)-6,6-dibromo-1-O-trityl-hex-5-ene-1,2,3-triol (12) with this alkyllithium reagent led to (2R,3S)-1-O-trityl-hex-5-yne-1,2,3-triol (23) in 87% yield. Other glyco-1-ynitols were obtained with satisfying yields (64-87%).     

Modular synthesis of 1,4-diketones through regioselective bis-acylation of olefins by merging NHC and photoredox catalysis

Efficient and modular synthesis of structurally diverse 1,4-diketones from readily available building blocks represents an essential but challenging task in organic chemistry. Herein, we report a multi-component, regioselective bis-acylation of olefins by merging NHC organocatalysis and photoredox catalysis. With this protocol, a broad range of 1,4-diketones could be rapidly assembled using bench-stable feedstock materials. The robustness of this method was further evaluated by sensitivity screening, and good reproductivity was observed. Moreover, the diketone products could be readily converted into functionalized heterocycles, such as multi-substituted furan, pyrrole, and pyridazine. Mechanistic investigations shed light on the NHC and photoredox dual catalytic radical reaction mechanism.     

Higher Order Cuprate Species( Ⅱ )——Stereospecific Carbocupration of Terminal Alkynes and Its Synthetic Utility for ( ± )-Ipsenol and (E)-β-Farnesene

The stereospecific carbocupration of terminal alkynes via higher order cuprates to give 1,1'-disubstituted olefins with 99% configuration purity is described. Its synthetic utility as a general method for the preparation of substituted olefins is further illustrated by the direct synthesis of (±)-ipsenol and (E)-β-farnesene with highly geometric purity of the carbon-carbon double bond.     

Syntheses of Carboxylic Acids from 1, 1-Dichloroehylene

Many β-alkyl- and β-arylpropionic acids are readily obtainable by the reaction of secondary or tertiary alcohols, esters of these, or olefins with the inexpensive 1, 1-dichloroethylene in sulfuric acid. The success of the synthesis depends on the bulk and energy of the carbonium ion intermediate formed from the alcohols or olefins. With carbonium ions having one H atom attached to the carbonium C atom, electrophilic substitution of the 1,1-dichloroethylene takes place to a small extent. Dicarboxylic acids and carboxylic acids with higher molecular weights are sometimes formed as a result of side reactions.     

Regio- and stereo-selective synthesis of multi-substituted 3-pyrrolines

A regio-and stereo-selective synthesis of multi-substituted 3-pyrrolines has been developed.The multi-substituted 3-pyrrolines were synthesized in good yields by 1,3-dipolar cycloaddition of methyl 2-(phenylselanyl)acrylate with azomethine ylides,followed by N-acylation and oxidation-elimination of phenylseleno group.     

手性联萘酚配合物催化的缺电子烯烃不对称环氧化反应*

缺电子烯烃的不对称环氧化反应是有机合成领域最具有挑战性的课题之一。手性联萘酚配体所修饰的催化剂是一种很优异的C2轴对称手性诱导源,可以催化各种α,β－不饱和羰基化合物如α,β－不饱和酮、α,β－不饱和羧酸脂等的不对称环氧化反应,具有良好的催化活性和对映选择性。本文对由手性联萘酚类配体所修饰的小分子催化剂、聚合物负载的催化剂和自负载催化剂在不饱和羰基化合物的催化不对称环氧化反应中的应用进行了综述,探讨了催化剂结构、配位金属原子、添加物、氧化剂、溶剂和反应温度等因素对手性联萘酚催化剂催化效能和对映选择性的影响。     

Disulfide-Catalyzed Visible-Light-Mediated Oxidative Cleavage of C=C Bonds and Evidence of an Olefin–Disulfide Charge-Transfer Complex

A photocatalytic method for the aerobic oxidative cleavage of C=C bonds has been developed. Electron-rich aromatic disulfides were employed as photocatalyst. Upon visible-light irradiation, typical mono- and multi-substituted aromatic olefins could be converted into ketones and aldehydes at ambient temperature. Experimental and computational studies suggest that a disulfide–olefin charge-transfer complex is possibly responsible for the unconventional dissociation of S−S bond under visible light.     

Synthesis of functionalized vinyl boronates via ruthenium-catalyzed olefin cross-metathesis and subsequent conversion to vinyl halides

Functionalized vinyl pinacol boronates suitable for Suzuki cross-coupling reactions are synthesized using ruthenium-catalyzed olefin cross-metathesis of 1-propenyl pinacol boronate and various alkenes, including functionalized and 1,1-disubstituted alkenes. The resultant boronate cross products are stereoselectively transformed into predominantly Z-vinyl bromides and E-vinyl iodides. The vinyl bromides may be synthesized in a two-step, one-pot synthesis from a variety of olefins, resulting in a Z-selective formal vinyl bromide cross-metathesis reaction.     

Lewis acid-activated chiral leaving group: enantioselective electrophilic addition to prochiral olefins

A new strategy using a BINOL derivative as a chiral leaving group and Lewis acid has been developed for enantioselective alkylation of prochiral olefins. (R)-2,2'-Bis[2-(trimethylsilyl)ethoxymethyl]-1,1'-binaphthol is demonstrated to be an effective reagent for enantioselective hydroxymethylation of silyl enol ethers and trisubstituted alkenes. Electrophilic addition to prochiral olefins is accompanied by cleavage of an acetal that is dual activated by SnCl4 and the delta-effect of silicon through the S(N)2 substitution process. Enantioselective synthesis of cyclic terpenes is also described using this strategy.     

Ligand-Enabled Nickel-Catalyzed Redox-Relay Migratory Hydroarylation of Alkenes with Arylborons

A redox-relay migratory hydroarylation of isomeric mixtures of olefins with arylboronic acids catalyzed by nickel complexes bearing diamine ligands is described. A range of structurally diverse 1,1-diarylalkanes, including those containing a 1,1-diarylated quaternary carbon, were obtained in excellent yields and with high regioselectivity. Preliminary experimental evidence supports the proposed non-dissociated chainwalking of aryl-nickel(II)-hydride species along the alkyl chain of alkenes before selective reductive elimination at a benzylic position. A catalyst loading as low as 0.5 mol % proved to be sufficient in large-scale synthesis while retaining high reactivity, highlighting the practical value of this transformation.