碳硼烷硼氢键选择性官能团化的研究进展

由于独特的三维立体结构、硼含量高、良好的热稳定性和化学稳定性等特点,碳硼烷及其衍生物在材料、催化、医药、超分子和配位化学等领域应用广泛,因此发展高效、高区域选择性的碳硼烷B-H键的官能团化的方法学备受硼化学家的关注。本文对近年来碳硼烷B-H键的官能团化的反应类型及相关反应机理予以论述,希望为后续研究提供可靠的参考。     

过渡金属催化硼-氢键活化合成含硼-杂原子键邻碳硼烷衍生物的研究进展

十二顶点碳硼烷是一类含有碳、氢及硼原子的簇合物,具有特殊的热稳定性和化学稳定性,在医药、材料、能源、配位化学及金属有机化学中都得到广泛的应用.近年来,过渡金属催化的碳硼烷直接硼-氢键活化发展迅速,为硼顶点选择性官能团化提供了一系列新的高效路径.总结了利用过渡金属催化硼-氢键活化策略来实现邻碳硼烷硼-硼、硼-氮、硼-氧、硼-硫及硼-卤键构建的研究进展,同时对部分反应机理进行了讨论,并就该研究领域所面临的挑战和发展前景进行了展望.     

碳硼烷硼端衍生物的合成与表征

在路易斯酸催化下,碳硼烷分别与对氰基溴化苄、三苯基膦在甲苯溶液里回流,前者反应中,制备得碳硼烷的硼端与对氰基苄基中的亚甲基直接偶联的产物1,通过调整催化剂的含量,可以显著地提高含B-Cl键的产物2的产率;与三苯基膦的反应中,碳硼烷失去一个硼顶,并与三苯基膦中的P原子直接偶联,生成含B-P键的巢式碳硼烷衍生物3。对此两类化合物进行了核磁、质谱、红外及单晶衍射等表征。化合物1和2中均发现碳硼烷的CH与N形成CH…N氢键和CH…π的弱作用,其中化合物2中,还存在CH…Cl。在巢式化合物3中,发现碳硼烷的CH参与了罕见的CH…HC相互作用。这类反应成功合成了含有B-C、B-Cl、B-P键的碳硼烷衍生物。     

膦氧导向钯催化邻碳硼烷Heck类型的官能团化反应（英文）

邻-碳硼烷的选择性官能团化是碳硼烷化学中的一个热点.由于邻-碳硼烷特殊的三维芳香性,其在聚集诱导发光材料、非线性发光材料以及其他功能材料领域有着广泛的应用.在邻碳硼烷上引入π-共轭体系能进一步扩大其在发光材料领域的应用.报道了膦氧导向钯催化邻碳硼烷Heck类型的单烯基化反应.     

钯催化硼-碳和硼-杂原子键构建一锅法合成双官能团化邻-碳硼烷※

碳硼烷是由碳氢和硼氢顶点组成的笼状分子, 在医药、能源和材料等领域有着重要应用, 但目前在碳硼烷硼顶点引入杂原子取代基的方法还较为有限. 基于此, 本工作从3-碘-邻-碳硼烷出发, 通过钯催化烯基化、金属迁移及后续与杂原子亲核试剂的偶联反应, 一锅法构筑硼碳键和硼杂原子键, 成功实现了一系列新型3-烯基-4-胺基/烷氧基/烷(芳)硫基-邻-碳硼烷衍生物的合成.     

基于B-H键的活化对含B-C、B-Cl、B-P键的碳硼烷硼端衍生物的合成与表征

在路易斯酸催化下,碳硼烷分别与对氰基溴化苄、三苯基膦在甲苯溶液里回流,前者反应中,制备得碳硼烷的硼端与对氰基苄基中的亚甲基直接偶联的产物1,通过调整催化剂的含量,可以显著地提高含B-Cl键的产物2的产率;与三苯基膦的反应中,碳硼烷失去一个硼顶,并与三苯基膦中的P原子直接偶联,生成含B-P键的巢式碳硼烷衍生物3。对此两类化合物进行了核磁、质谱、红外及单晶衍射等表征。化合物1和2中均发现碳硼烷的CH与N形成CH…N氢键和CH…π的弱作用,其中化合物2中,还存在CH…Cl。在巢式化合物3中,发现碳硼烷的CH参与了罕见的CH…HC相互作用。这类反应成功合成了含有B-C、B-Cl、B-P键的碳硼烷衍生物。     

碳硼烷化学发展之路

碳硼烷分子具有独特的笼状结构,能够表现出三维芳香性和稳定的物理化学性质,这使得碳硼烷不仅能够应用于有机硼化学及金属有机化学,而且在生物学、材料学等领域也有不错的应用前景。本文叙述了碳硼烷化学的发展历史、碳硼烷化合物的结构性质,并简要介绍了碳硼烷近年来在生物医学、发光材料以及催化剂领域的应用,希望对读者了解碳硼烷化学的新进展能够有所帮助。     

碳硼烷和碳硼炔金属配合物中金属-碳键的化学性质

碳硼烷和碳硼炔金属配合物中的金属-碳键具有不同于经典金属-碳键的化学性质.一方面,二十面体碳硼烷独特的电子和空间效应使得碳硼烷金属配合物中的金属-碳键不参与和不饱和分子的反应 另一方面,在一定条件下具有大空间位阻的碳硼笼可以诱导某些碳-碳偶联反应.然而,碳硼炔金属配合物中的金属-碳键能与多种不饱和分子发生反应,其反应模式取决于中心金属离子的电子构型.本文简要总结了我们近期在这方面的研究进展.     

基于B-H键的活化对含B-C、B-Cl、B-P键的碳硼烷硼端衍生物的合成与表征

在路易斯酸催化下,碳硼烷分别与对氰基溴化苄、三苯基膦在甲苯溶液里回流,前者反应中,制备得碳硼烷的硼端与对氰基苄基中的亚甲基直接偶联的产物1,通过调整催化剂的含量,可以显著地提高含B-Cl键的产物2的产率;与三苯基膦的反应中,碳硼烷失去一个硼顶,并与三苯基膦中的P原子直接偶联,生成含B-P键的巢式碳硼烷衍生物3。对此两类化合物进行了核磁、质谱、红外及单晶衍射等表征。化合物1和2中均发现碳硼烷的CH与N形成CH…N氢键和CH…π的弱作用,其中化合物2中,还存在CH…Cl。在巢式化合物3中,发现碳硼烷的CH参与了罕见的CH…HC相互作用。这类反应成功合成了含有B-C、B-Cl、B-P键的碳硼烷衍生物。     

碳硼烷双酚二缩水甘油醚的合成与表征及耐高温性能研究

以o-(3)和m-碳硼烷双酚(4)为原料,经两步法合成了o-(1)和m-碳硼烷双酚二缩水甘油醚(2),FTIR、1H-NMR、GPC和环氧值测试都表明得到了预期结构的碳硼烷环氧树脂.固化反应动力学研究结果显示,1/DDS和2/DDS体系的反应活化能(Ea)分别为79.0和67.1 k J·mol-1,比E-51/DDS略高,说明碳硼烷结构的存在降低了环氧树脂的反应活性.以Ea结果为依据,确定了1(2)/DDS体系的固化工艺为180℃/2h+200℃/2h.热分析结果表明,以DDS为固化剂时,1和2的Tg分别为175.8和167.6℃,高于TDE-85的154.1℃.TGA结果表明,2/DDS固化物在空气气氛下700℃的残炭率高达78.7%,说明碳硼烷结构的存在极大提高了环氧树脂高温稳定性.碳硼烷环氧树脂空气气氛中的高温残炭率比氮气中高,原因是碳硼烷结构中的B-H键与空气中的氧气反应生成B—O—B结构,因而提高了残炭率,并在一定程度上延缓了体系的失重.     

Facial Synthesis of o‐Carborane‐Substituted Alkenes and Allenes by a Regioselective Ene Reaction of 1,3‐Dehydro‐o‐carborane

1,3‐Dehydro‐o‐carborane is a useful synthon for selective cage boron functionalization of o‐carboranes. It reacts readily with alkenes or alkynes to give a variety of cage B(3)‐alkenyl/allenyl o‐carboranes by ene reactions in very high yields and excellent regioselectivity. This can be ascribed to the highly polarized cage C?B multiple bond, which lowers the activation barriers of the ene reaction.     

1,3‐Dehydro‐o‐Carborane: Generation and Reaction with Arenes

Like the importance of benzyne, witnessed in modern arene chemistry for decades, 1,2‐dehydro‐o‐carborane (o‐carboryne), a three‐dimensional relative of benzyne, has been used as a synthon for generating a wide range of cage, carbon‐functionalized carboranes over the past 20 years. However, the selective B functionalization of the cage still represents a challenging task. Disclosed herein is the first example of 1,3‐dehydro‐o‐carborane featuring a cage C? B bond having multiple bonding characters, and is successfully generated by treatment of 3‐diazonium‐o‐carborane tetrafluoroborate with non‐nucleophilic bases. This presents a new methodology for simultaneous functionalization of both cage carbon and boron vertices.     

One‐pot Annulation for Biaryl‐fused Monocarba‐closo‐dodecaborate through Aromatic B−H Bond Disconnection

We have developed a one‐pot annulation reaction of monocarba‐closo‐dodecaborate with cyclic diaryliodonium salts to afford biaryl‐fused derivatives. Aryl functionalities are introduced at both the 1‐carbon and unreactive ortho‐boron vertices of the “σ‐aromatic” carborane cage without the need for pre‐functionalization. DFT calculations revealed that the palladium‐catalyzed C?B bond‐formation step in this process proceeds through a concerted metalation–deprotonation (CMD)‐type pathway for the B?H bond disconnection on the aromatic cage, though such bonds are generally regarded as hydridic.     

NCBBH…HNa(H2O)n和CNBBH…HNa(H2O)n(n=1~5)结构与性质的理论研究

为了探索缺电子B-H键作为质子供体形成双氢键复合物的溶剂化效应,分别采用DFT-B3LYP/6-311++G**和CCSD(T)/6-311++G**方法对NCBBH…HNa和CNBBH…HNa及其水合物NCBBH…HNa(H2O)n和CNBBH…HNa(H2O)n(n=1~5)进行了结构优化和相互作用能计算,并利用AIM(atom in molecule)方法分析了H…H键特征,借助前线分子轨道理论探讨了水合物中双氢键形成H-H共价键的本质。结果表明:随着H2O分子数的增加,B-H键拉长,H…H距离缩短,双氢键由离子型向共价型过渡;当H2O分子数达到4时,双氢键相互作用能和NCBBH…HNa与水分子间的相互作用能分别达到-374.21和-306.50 kJ.mol-1,形成了H-H共价键;缺电子B-H键作为质子供体形成双氢键复合物的水合物析出H2的能力比FH…HLi(H2O)n弱。     

Steering Site-Selectivity in Transition Metal-Catalyzed C−H Bond Functionalization: the Challenge of Benzanilides

Selective C−H bond functionalization catalyzed by metal complexes have completely revolutionized the way in which chemical synthesis is conceived nowadays. Typically, the reactivity of a transition metal catalyst is the key to control the site-, regio- and/or stereo-selectivity of a C−H bond functionalization. Of particular interests are molecules that contain multiple C−H bonds prone to undergo C−H bond activations with very similar bond dissociation energies at different positions. This is the case of benzanilides, relevant chemical motifs that are found in many useful fine chemicals, in which two C−H sites are present in chemically different aromatic fragments. In the last years, it has been found that depending on the metal catalyst and the reaction conditions, the amide motif might behave as a directing group towards the metal-catalyzed C−H bond activation in the benzamide site or in the anilide site. The impact and the consequences of such subtle control of site-selectivity are herein reviewed with important applications in carbon-carbon and carbon-heteroatom bond forming processes. The mechanisms unraveling these unique transformations are discussed in order to provide a better understanding for future developments in the field of site-selective C−H bond functionalization with transition metal catalysts.     

C（sp3）-H bond functionalization of oximes derivatives via 1,5-hydrogen atom transfer induced by iminyl radical

Oximes derivatives have been vastly used in organic synthesis. In this review, C（sp³）-H bond functionalization of oximes derivatives via iminyl radical induced 1,5-hydrogen atom transfer was discussed. According to the different type of products, this review was divided into three parts:（1） C（sp³）-H bond functionalization for C-C bond formation.（2） C（sp³）-H bond functionalization for C-N bond formation.（3） C（sp³）-H bond functionalization for C-S, C-F b...     

光/电化学氧化诱导C–H键官能团化

C–H键活化及其官能团化一直被认为是合成化学的圣杯,光/电氧化诱导C–H键官能团化反应为追求更为绿色、原子经济性、步骤经济性更高的现代合成化学提供了新思路.我们借助可见光或电化学氧化诱导策略实现了直接C–H键官能团化,即底物无需预官能团化,无需外加氧化剂,可直接实现碳–碳以及碳–杂键的构建.通过光/电化学氧化诱导策略使得反应在更为温和的条件下进行,能够兼容更多官能团,并且为合成化学提供一条新的途径.近些年,该策略已经应用于不同化学环境C–H官能团化构建多种化学键.本文结合该领域的代表性工作,重点介绍本课题组近些年在光/电氧化诱导C–H键官能团化反应上的研究进展,并对这一领域的前景进行了展望.     

Rhodium(III)‐Catalyzed Alkenylation–Annulation of closo‐Dodecaborate Anions through Double B−H Activation at Room Temperature

1,2,3‐Trisubstituted closo‐dodecaborates with B?O, B?N, and B?C bonds as well as a fused borane oxazole ring have been synthesized by rhodium‐catalyzed direct cage B?H alkenylation and annulation of ureido boranes in the first reported example of regioselective B?H bond functionalization of the [B₁₂H₁₂]^2? cage by transition‐metal catalysis. This reaction proceeded at room temperature under ambient conditions and exhibited excellent selectivity for efficient monoalkenylation with good functional‐group tolerance. The urea moiety enabled B?H activation by acting as a directing group, was incorporated in the oxazole ring in situ, and also avoided multiple alkenylation. A possible mechanism is proposed on the basis of the isolation of a rhodium agostic intermediate and control experiments.     

Rhodium boryl complexes in the catalytic, terminal functionalization of alkanes

A series of studies have been conducted by experimental and theoretical methods on the synthesis, structures, and reactions of CpRh boryl complexes that are likely intermediates in the rhodium-catalyzed regioselective, terminal functionalization of alkanes. The photochemical reaction of CpRh(eta(6)-C(6)Me(6)) with pinacolborane (HBpin) generates the bisboryl complex CpRh(H)(2)(Bpin)(2) (2), which reacts with neat HBpin to generate CpRh(H)(Bpin)(3) (3). X-ray diffraction, density functional theory (DFT) calculations, and NMR spectroscopy suggest a weak, but measurable, B-H bonding interaction. Both 2 and 3 dissociate HBpin and coordinate PEt(3) or P(p-Tol)(3) to generate the conventional rhodium(III) species CpRh(PEt(3))(H)(Bpin) (4) and CpRh[P(p-tol)(3)](Bpin)(2) (5). Compounds 2 and 3 also react with alkanes and arenes to form alkyl- and arylboronate esters at temperatures similar to or below those of the catalytic borylation of alkanes and arenes. Further, these compounds were observed directly in catalytic reactions. The enthalpies and free energies for generation of the 16-electron intermediate and for the C-H bond cleavage and B-C bond formation have been calculated with DFT. These results strongly suggest that the C-H bond cleavage process occurs by a metal-assisted sigma-bond metathesis mechanism to generate a borane complex that isomerizes if necessary to place the alkyl group cis to the boryl group. This complex with cis boryl and alkyl groups then undergoes B-C bond formation by a second sigma-bond metathesis to generate the final functionalized product.