Competition between C-C and C-H Activation in Reactions of Neutral Nickel Atom with Cycloalkanes （n = 3-7）

A theoretical investigation of the reaction mechanisms for C-H and C-C bond activation processes in the reaction of Ni with cycloalkanes C,,H2. （n = 3-7） is carried out. For the Ni ＋ CnH2, （n = 3, 4） reactions, the major and minor reaction channels involve C-C and C-H bond activations, respectively, whereas Ni atom prefers the attacking of C-H bond over the C-C bond in CnH2n （n = 5=7）. The results are in good agreement with the experimental study. In all cases, intermediates and transition states along the reaction paths of interest are characterized, It is found that both the C-H and C-C bond activation processes are proposed to proceed in a one-step manner via one transition state. The overall C-H and C-C bond activation processes are exothermic and involve low energy barriers, thus transition metal atom Ni is a good mediator for the activity of cycloalkanes CnH2n （n = 3 -7）.

Oxidative co-dehydrogenation of ethane and propane over h-BN as an effective means for C-H bond activation and mechanistic investigations

Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.

Protecting-group-free ortho-C–H borylation of anilines enabled by mesoionic carbene-Ir complex

We describe an iridium-catalyzed ortho-selective C–H borylation of unprotected anilines.The employing strongσ-donating cyclometalated mesoionic carbene as C^C bidentate ligand is crucial for the high ortho-selectivity.Computational studies support outer-sphere X–H⋅⋅⋅O_(boryl) hydrogen bond interactions,which are strengthened by bidentate C^C ligand introduction.The method shows broad substrate scope and high functional group tolerance.

2-(3-氯-1-乙基-1H-吡唑-4-基)嘧啶-4-胺盐酸盐高效合成工艺研究

嘧啶和吡唑类化合物是两类重要的杂环分子,在医药,农药,材料等领域有广泛的应用。为了支持公司新药研发,本文开发了关键中间体F 2-(3-氯-1-乙基-1H-吡唑-4-基)嘧啶-4-胺盐酸盐的高效合成路线。以N-乙基-3-氨基吡唑和2-氯-4-氨基嘧啶为起始原料,主路线分别经过Sandmeyer反应,NBS亲电取代反应,硼酸酯化反应,Suzuki偶联反应和脱保护反应。本文重点对硼酸酯化反应,侧链氨基保护反应和Suzuki反应进行研究,可以高效合成目标产物。

Metal-Free Synthesis of 2-Aminobenzothiazoles via I2-Catalyzed Tandem Cyclization Reaction of Amines and Carbon Disulfide

Comprehensive Summary,A convenient approach for the construction of 2-aminobenzothiazoles via I2-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed.The present approach starts from simple and readily available starting materials,affording a series of 2-aminobenzothiazoles in up to 89%yields under metal-free conditions.In this work,C—H/N—H functionalization was achieved and multiple C-hetero bonds were successfully constructed in one pot.

2-氯-4-异丙基氨基-5-(4,4,5,5-四甲基-1,3,2-二氧硼杂环戊烷-2-基)吡啶合成工艺研究

氨基吡啶类化合物是一类重要的医药中间体,在众多药物中有广泛的应用。为了支持公司新药研发,本文开发了关键中间体C(2-氯-4-异丙基氨基-5-(4,4,5,5-四甲基-1,3,2-二氧硼杂环戊烷-2-基)吡啶)的高效合成路线。以5-溴-2,4-二氯吡啶作为起始原料,分别经过亲核芳香取代和钯催化硼酸酯化反应获得目标产品。第一步反应优化了投料比,温度,时间,可以有效避免二取代杂质。在优化Miyaura硼酸酯化反应过程中,使用公司高通量催化平台,筛选出醋酸钯/三苯基膦的催化体系组合,可以高效合成目标产物。通过简单的工艺参数优化,两步收率达到80.9%。本合成工艺具有反应干净,后处理简单,产品纯度好等优点。

Metal-free directed C-H borylation of 2-(N-methylanilino)-5-fluoropyridines and 2-benzyl-5-fluoropyridines

A novel method for metal-free C-H borylation of 2-(N-methylanilino)-5-fluoropyridines and 2-benzyl-5-fluoropyridines has been reported. The 5-fluoropyridine directed borylation reaction exhibited high efficiency and site exclusivity. The useful protocol could be executed on a gram-scale easily and the borylated products showed good derivatization applications. Moreover, the practicality of the strategy was expanded by the fact that the directing group could be removed in an acceptable yield.

新型含硼聚芳醚酮的制备、性能及在偶氮聚芳醚酮合成中的应用

利用双酚A型聚芳醚酮与联硼酸频哪醇酯在[Ir(COD)Cl]2和4,4'-二叔丁基-2,2'-联吡啶催化下反应,制备了新型含硼酸酯双酚A型聚芳醚酮,通过控制联硼酸频哪醇酯的投入量来实现硼酸酯的定量引入.再经过高碘酸钠作用得到含硼酸双酚A型聚芳醚酮,最后,通过高效Suzuki-Miyaura反应将偶氮定量引入到聚芳醚酮主链.利用核磁共振(1H NMR)确定了聚合物的结构,利用凝胶渗透色谱(GPC)确定了聚合物的分子量,利用差示扫描量热分析(DSC)和热失重分析(TGA)研究了聚合物的热性能,利用紫外-可见光谱(UVVis)研究了偶氮聚芳醚酮的光谱学性能.

频哪醇联硼酸酯B_2pin_2在偶联反应中的应用

标题化合物是一类非常有用的硼试剂。综述了B2pin2在不同过渡金属催化下与不同有机底物生成不同的有机硼中间体,并且通过硼中间体转化为各类有机化合物。同时列举了一些重要的硼中间体化合物(如烯硼、烯丙基硼、1,3-丁二烯硼化合物)的合成。

Transition Metal Catalyzed Direct Oxidative Borylation of C--H Bonds

Organoboron is well-developed and broadly utilized organometallic reagents in organic synthesis due to its extraordinary performances in transition-metal catalyzed C-C and C-X bonds construction. Catalytic C--H borylation and further transformations catalyzed by transition metal catalysts in the absence of oxidants were well studied in decades. However, as known, transition metal catalyzed oxidative C-H borylations were not reviewed up to date. In this article the oxidative borylation of C（sp2）-H and C（sp3）-H bonds were summarized and their mechanisms were also accounted.

过渡金属Ni催化的硼化反应研究进展

介绍了近年来过渡金属Ni催化的硼氢化反应、双硼化反应、β-硼化反应、硼化开环反应以及硼化偶联反应的研究进展,并对相关的反应机理进行了讨论。

An Olefinic 1,2-α-Boryl Migration Enables 1,2-Bis(boronic esters)via Radical-Polar Crossover Reaction

A radical-induced 1,2-α-boryl migration through radical polar crossover reactions has been described.In this work,in situ formed vinyldiboron“ate”complexes from alkenyl Grignard reagent and diborylalkanes react with commercial radical precursors under light initiation.This three-component process enables diborylation of alkene.This protocol features high atom economy,a broad substrate scope as well as good functional group toleration with mild conditions.

Iron-Catalysed C(sp^(2))-H Borylation with Expanded Functional Group Tolerance

Arene C(sp^(2))-H bond borylation offers direct and efficient access to aryl boronic esters.Using in situ catalyst activation and photoirradiation,the iron-catalysed C(sp^(2))-H borylation reaction of carboarenes,pyrroles,and indoles has been developed using only bench-stable pre-catalysts and reagents.Good functional group tolerance was observed including those not reported using previous methods(ArNH_(2),ArOH,ArSiR_(3),ArP(O)(O)_(2),ArC(O)NR_(2)).Mechanistic studies revealed iron-catalysed reductive deoxygenation,C—F protodefluorination,and a demethylation of aryl methyl ethers by C—O sigma bond hydroboration.

含硼吲哚的合成及其应用研究进展

总结了近几年来相关文献中的含硼化合物的合成方法,重点介绍了硼化吲哚合成及其在BNCT中的应用及发展。同时也综述了目前含硼药物、BNCT法治疗状况及其发展中存在的问题。

Photocatalytic Decarboxylative Minisci Reaction Catalyzed by Palladium-Loaded Gallium Nitride

The decarboxylative Minisci reaction is a versatile tool for the direct C-H alkylation of heteroarenes,where stoichiometric amounts of oxidants or expensive,precious metal reagents are commonly used.Herein,we reported a photodriven decarboxylative Minisci reaction enabled by a gallium nitride-based heterogeneous photocatalyst under mild conditions.This method can be effectively applied to a broad substrate scope of acids,including primary,secondary,and tertiary carboxylic acids and N-heteroarenes effectively.The practicability and robustness of the approach are demonstrated for the functionalization of biologically active compounds.

Recent advances in visible light-mediated chemical transformations of enaminones

Enaminones,which possesses both the nucleophilic enamine as well as electrophilic enone structures,are well known versatile building blocks in organic synthesis.Meanwhile,visible light-mediated reactions have emerged as useful synthetic strategy with enhanced sustainability.Around the last decade,various photochemical transformations of enaminones have been developed to construct cyclic or acyclic compounds.In this review,we describe the recent advances in visible light-mediated chemical transformations of enaminones.Detailed discussion on the reaction mechanism of the related reactions is given to provide guide to the reader.Finally,a summary on the existing challenges and the future outlook towards the development of practical photocatalytic reactions of enaminones is also presented.

Multicomponent remote C(sp^(2))–H bond addition by Ru catalysis:An efficient access to the alkylarylation of 2H-imidazoles

Sequential C–H bond addition with two different coupling partners is a powerful method for the rapid and modular construction of complex molecules based on simple starting materials.Herein,an efficient ruthenium-catalysed multicomponent long-range C–H functionalization of 2H-imidazoles was developed.This protocol showed good substrate suitability and yielded alkyl arylation products with potential biological activity.

Radical-Mediated Selective Functionalization of Unactivated Primary C-H Bonds

Radical-mediated sp^(3)C—H functionalization has found broad applications in synthesis and late-stage derivatization of complex molecules.The site-selectivity of a given reaction is mainly dictated by the bond strength,polarity and steric accessibility of diverse C—H bonds as well as the characters of hydrogen atom acceptors.Unactivated sp^(3)C—H bonds usually follow the relative reactivity sequence of tertiary>secondary>primary,which is even recognized as the innate preferences of certain substrates.The development of innovative methods capable of overriding the“inherent”site-selectivity is exceedingly attractive.Although it has been demonstrated that secondary C—H bonds could be selectively converted in the presence of weaker tertiary C—H bonds by tuning the steric and electronic properties of hydrogen atom acceptors,the selective activation of primary C—H bonds remains a daunting challenge.Herein,we highlight the recently emerging attempts towards this goal by interrogating the steric effect of hydrogen atom acceptors.

New progress in theoretical studies on palladium-catalyzed C-C bond-forming reaction mechanisms

This review reports a series of mechanistic studies on Pd-catalyzed C-C cross-coupling reactions via density functional theory(DFT) calculations.A brief introduction of fundamental steps involved in these reactions is given,including oxidative addition,transmetallation and reductive elimination.We aim to provide an important review of recent progress on theoretical studies of palladium-catalyzed carbon-carbon cross-coupling reactions,including the C-C bond formation via C-H bond activation,decarboxylation,Pd(Ⅱ)/Pd(Ⅳ) catalytic cycle and double palladiums catalysis.

Catalytic asymmetric Catellani-type reaction: A powerful tool for axial chirality construction

This highlight summarizes a recent development of a catalytic enantioselective Catellani-type reaction for the synthesis of axially chiral biaryls.The chirality induction is solely governed by chiral norbornene ligand in the Pd mediated ortho C–H functionalization and ipso cross-coupling transformation.The preparative power of the methodology is demonstrated as a powerful manifold for the divergent synthesis of structurally diverse axially chiral biaryls and chiral fluorenols.