过渡金属催化C—CN键偶联反应的研究进展

过渡金属催化的氰化反应是合成有机氰化物非常重要的手段之一.综述了近年来过渡金属催化C—CN键偶联反应的研究进展,主要包括芳基、烯基卤化物及拟卤化物,芳基硼酸,烯烃,炔烃,芳烃等的氰化反应及其机理的探讨.     

过渡金属催化氟代烯烃参与的交叉偶联反应进展

过渡金属催化（类）卤化物和不同金属试剂的交叉偶联反应是构建不同类型碳碳键和碳杂原子键的重要方法之一。该类反应一般使用活性较高的氯、溴、碘或类卤化物作为亲电试剂,尽管C—F键的键能较强,利用过渡金属直接活化较为惰性的芳基C—F键并参与实现的交叉偶联反应已有较多报道。此外,近期的研究表明,也可以通过直接活化烯基C—F键并催化实现该类底物参与不同类型的交叉偶联反应,从而进一步拓展了交叉偶联反应的底物适用范围,并应用于具有高附加值精细化学品的选择性合成。本文围绕钯或镍催化活化单氟或者多氟烯烃等底物参与的Negishi、Suzuki-Miyaura、Kumada、Hiyama和Sonogashira等5类交叉偶联反应,通过探讨已有方法的反应机理及其适用范围,综述了该领域的研究进展并进行了展望。     

过渡金属催化C—H键氟化反应研究进展

有机氟化物由于其特殊的性质被广泛应用于医药、农药以及材料领域中,然而由于氟元素的强电负性使得引入氟原子充满了挑战.过渡金属催化的碳氢键氟化反应由于其避免了使用预官能化的底物,而且对自然界中最广泛存在的碳氢键进行直接活化官能化,因此与传统的过渡金属催化的偶联反应相比在原子经济性、反应多样性以及环境友好性等方面都具有突出的优势.近十年来,利用过渡金属催化碳氢键氟化策略已经成为构建碳氟键重要手段和研究热点.作者较全面地综述近年来过渡金属催化的碳氟键构建的研究进展及合成应用,对该领域所存在的问题和局限性进行了总结,并对今后的发展做了展望.     

钯催化苯胺衍生物与N-氟代苯磺酰亚胺的C—H胺化反应

导向的过渡金属催化芳烃C—H官能化反应是近年来发展起来的一种非常重要的芳烃定向官能化方法,然而,其固定的邻位活化模式限制了该方法的广泛应用.因此,发展一种导向的过渡金属催化的适用于芳烃任意位置,包括邻位、间位、对位以及苄位C—H的官能化方法,是非常具有挑战性的研究课题.芳胺及其衍生物在医药、农药、     

过渡金属催化的不对称交叉脱氢偶联反应研究进展

C—C键的形成是药物合成过程中重要的研究内容之一.交叉脱氢偶联直接利用不同反应底物中的C—H键在氧化条件下进行交叉偶联反应形成C—C键,反应过程中避免了反应底物的预先官能化,是构建新的碳-碳键简洁、高效的合成路径,原子利用率高、环境友好,具有重大的理论意义和应用价值.综述了目前过渡金属催化的不对称交叉脱氢偶联反应,重点阐述过渡金属与配体在反应的立体选择性中的应用.     

芳基锡烷的合成研究进展

芳基锡烷化合物是参与构筑功能分子中芳基碳碳键和碳杂原子键的一类重要合成中间体. 其在药物化学、材料科学以及有机合成中都具有重要应用, 因此发展其高效新颖的合成方法具有重要的意义. 根据反应机理的类型, 综述了近些年来合成芳基锡烷的方法, 包括(1)芳香亲核试剂的锡化反应; (2)芳香亲电试剂的锡化反应; (3)过渡金属催化的锡化偶联反应; (4)芳基自由基中间体介导的锡化反应; (5)炔烃的环化和串联的锡化反应. 最后, 进一步分析了未来合成芳基锡烷的研究趋势.     

Pd催化(杂环)芳基羧酸脱羧的偶联反应研究进展

羧酸具有无毒、廉价易得、稳定易存储等特点,有关过渡金属Pd催化(杂环)芳基羧酸脱羧的偶联反应在本世纪来得到了迅速发展,大有取代传统偶联反应之势.本文综述了Pd催化(杂环)芳基羧酸脱羧与多种底物的偶联反应,如烯、芳基卤化物、芳烃,三氟芳基硼酸盐等底物,并对相关的反应机理进行了探讨.     

可见光诱导的无过渡金属催化交叉脱氢偶联反应研究进展

交叉脱氢偶联反应通过两种不同的X—H键直接偶联生成新的化学键,具有优异的步骤经济性和原子经济性.传统交叉脱氢偶联反应通常以过渡金属催化,存在催化剂昂贵及污染严重等问题.可见光诱导电子转移也是实现X—H键直接官能化的有效途径.可见光诱导的无过渡金属催化交叉脱氢偶联反应因具有清洁安全、步骤和原子经济性高等优点从而受到广泛关注.根据成键类型分类,综述了该类反应的研究进展,并对其前景进行了展望.     

配体促进的过渡金属催化芳烃远程meta-C—H键官能化反应研究进展

过渡金属催化C—H活化反应中,配体能够对催化中心的空间及电子效应进行调控,从而实现芳烃C—H键的选择性官能化.近年来,配体促进芳烃远程C—H键官能化反应研究有了新的进展.对近几年来配体促进的过渡金属催化芳烃远程meta-C—H键选择性官能化反应进行了系统总结,并对该研究领域的局限性和未来的发展前景进行总结和展望.     

铜催化硼试剂参与的烯烃多组分双官能化研究进展

烯烃的多组分双官能化是一类高效快速构建结构多样性分子的重要有机反应,具有原子经济性高、底物范围广及条件温和等诸多优点,近年来成为有机合成领域的主要研究热点.许多金属或非金属催化条件下的烯烃多组分双官能化反应已经被大量报道,借助手性配体,有的反应还成功地实现了不对称双官能化.然而,与贵重金属催化剂(钌、铑、铱、钯、银)相比,价格低廉的过渡金属(铁、钴、镍、铜、锰)催化的有机反应更加受到人们的青睐.考虑到铜催化剂和有机硼试剂在有机合成中的应用,针对近三年来铜催化下有机硼试剂参与的烯烃多组分双官能化反应进行了综述,并对该领域面临的挑战和发展方向进行了展望.     

芳香化合物直接催化氧化偶联反应研究进展

总结了近年来非官能化芳香化合物直接催化氧化偶联合成联芳香化合物的研究进展,包括芳香化合物的自身偶联、交叉偶联以及分子内偶联反应,同时对反应中涉及的机理也进行了详细地讨论.     

Oxidative intramolecular coupling of 2, 3-disubstituted phenyl acrylic acids and derivatives promoted by di-tert-butylperoxide

Polymethoxy-substituted phenanthrene-9-carboxylic acids or their methylate are key intermediates for the synthesis of tylophora alkaloids and their analogs. An intramolecular oxidative coupling reaction of unfunctionalized 2,3-disubstituted phenyl acrylic acids and derivatives promoted by di-tert-butylper- oxide gave above intermediates in high yields. The mild reaction conditions and easy purification procedures of this method provide a new approach for the synthesis of phenanthrenes.     

Synthesis of Chiral Triarylmethanes Bearing All‐Carbon Quaternary Stereocenters: Catalytic Asymmetric Oxidative Cross‐Coupling of 2,2‐Diarylacetonitriles and (Hetero)arenes

A direct and enantioselective oxidative cross‐coupling of racemic 2,2‐diarylacetonitriles with electron‐rich (hetero)arenes has been described, which allows for efficient construction of triarylmethanes bearing all‐carbon quaternary stereocenters with excellent chemo‐ and enantioselectivity. The reaction has an excellent functional group tolerance, and exhibits a broad scope with respect to both 2,2‐diarylacetonitrile and (hetero)arene components. The rich chemistry of the cyano group allows for facile synthesis of other valuable chiral triarylmethanes bearing all‐carbon quaternary centers that are otherwise difficult to access.     

甲烷在CaO—Li—CeO2催化剂上氧化偶联反应宏观动力学

本文报导在CaO-Li-CeO_2催化剂上甲烷氧化偶联反应的宏观动力学。在893-973K温度范围内测出了甲烷氧化偶联反应产物的生成速度及其对甲烷及氧分压的反应级数。根据这些数据计算出了甲烷转化和相应产物生成的表观活化能E。在此基础上对反应机理进行了初步探讨。     

(±)-Palstatin的首次全合成研究

以廉价易得的5-溴香草醛和2,4,6-三羟基苯乙酮为起始原料，首次方便,高效地合成了(±)-Palstatin (1).合成的关键步骤为SeO₂促进的氧化环化和Ag₂O催化的氧化偶联反应.     

Synthesis of Nitrogen-Containing Polyaromatics by Aza-Annulative π-Extension of Unfunctionalized Aromatics

Nitrogen-containing polycyclic aromatic compounds (N-PACs) are an important class of compounds in materials science. Reported here is a new aza-annulative π-extension (aza-APEX) reaction that allows rapid access to a range of N-PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow-up oxidative treatment with p-chloranil affords structurally diverse N-PACs, which are very difficult to synthesize. DFT calculations reveal that the aza-APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N-PACs into nitrogen-doped nanographenes and their photophysical properties are also described.     

TBAI/TBHP‐Promoted Generation of Malonyl Radicals: Oxidative Coupling with Styrenes Leads to γ‐Keto Diesters

A metal‐free protocol for oxidative coupling of malonic esters with styrenes to form γ‐keto diesters has been developed. Key to the success of this process is the generation of malonyl radicals from unfunctionalized malonic esters under organo‐catalysis conditions with TBAI and TBHP. This process tolerates both terminal and internal olefins with diverse malonic esters. It provides a new green metal‐free alternative to traditional metal mediated process for generation of malonyl radicals and there by γ‐keto diesters.     

Kinetic studies of the oxidative coupling of methane over the Mn/Na2WO4/SiO2 catalyst

Oxidative coupling of methane is a direct way to obtain C2 hydrocarbon,and Mn-Na-W/SiO2 catalyst is the most promising among all the catalysts.The 2%Mn/5%Na2WO4/SiO2 catalyst was prepared by the incipient wetness impregnation method.A 7-step heterogeneous reaction model of the oxidative coupling of methane to C2 hydrocarbons was conducted by co-feeding methane and oxygen at a total pressure of 1 bar over the catalyst.The kinetic measurements were carried out in a micro-catalytic fixed bed reactor.The kinetic data were obtained at the appropriate range of reaction conditions (4 kPa＜Po2 ＜20 kPa,20 kPa＜PCZH4 ＜80 kPa,800℃＜T＜900℃).The proposed reaction kinetic scheme consists of three primary and four consecutive reaction steps.The conversions of hydrocarbons and carbon oxides were evaluated by applying Langrnuir-Hinshelwood type rate equations.Power-law rate equation was applied only for the water-gas shift reaction.In addition,the effects of operating conditions on the reaction rate were studied.The proposed kinetic model can predict the conversion of methane and oxygen as well as the yield of C2 hydrocarbons and carbon oxides with an average accuracy of ±15%.     

Cover Feature: Redox-Active Guanidines in Proton-Coupled Electron-Transfer Reactions: Real Alternatives to Benzoquinones? (Chem. Eur. J. 70/2019)

Guanidino-functionalized aromatics (GFAs) are readily available, stable organic redox-active compounds. In this work we apply one particular GFA compound, 1,2,4,5-tetrakis(tetramethylguanidino)benzene, in its oxidized form in a variety of oxidation/oxidative coupling reactions to demonstrate the scope of its proton-coupled electron transfer (PCET) reactivity. Addition of an excess of acid boosts its oxidation power, enabling the oxidative coupling of substrates with redox potentials of at least +0.77 V vs. Fc⁺/Fc. The green recyclability by catalytic re-oxidation with dioxygen is also shown. Finally, a direct comparison indicates that GFAs are real alternatives to toxic halo- or cyano-substituted benzoquinones.     

Synthesis of Nitrogen‐Containing Polyaromatics by Aza‐Annulative π‐Extension of Unfunctionalized Aromatics

Nitrogen‐containing polycyclic aromatic compounds (N‐PACs) are an important class of compounds in materials science. Reported here is a new aza‐annulative π‐extension (aza‐APEX) reaction that allows rapid access to a range of N‐PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow‐up oxidative treatment with p‐chloranil affords structurally diverse N‐PACs, which are very difficult to synthesize. DFT calculations reveal that the aza‐APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N‐PACs into nitrogen‐doped nanographenes and their photophysical properties are also described.