73183-34-3Relevant articles and documents
The complex reactivity of β-diketiminato magnesium(i) dimers towards pinacolborane: Implications for catalysis
Jones, Dafydd D. L.,Matthews, Aidan J. R.,Jones, Cameron
, p. 5785 - 5792 (2019)
Reactions between the borane, HBpin (pin = pinacolato), and three magnesium(i) dimers, [{(ArNacnac)Mg-}2] (ArNacnac = [(ArNCMe)2CH]-; Ar = xylyl (Xyl), mesityl (Mes) or 2,6-diethylphenyl (Dep)), have been carried out in 2:1, 5:1 and 20:1 ratios. In all cases, NMR spectroscopic studies have revealed complex mixtures of many known and novel products from these reactions. From extracts of the crude reaction mixtures, low yields of ten compounds, representing six different types of complexes between β-diketiminato magnesium fragments and boron containing ligands, have been isolated and crystallographically characterised. These include unprecedented examples of compounds in which the γ-carbon of the β-diketiminate ligand has been activated by boron hydride fragments. In addition, boryloxide (OBpin), borate ([B(pin)2]- or [(pin)BH2]-), B-O bond ruptured [pinBH2]-, a diborane(5) dianion, or BH3 have been shown to be incorporated into the isolated complexes. The complexity of the products of the reported reactions are discussed in light of recently published patents and papers which report that magnesium(i) dimers act as efficient catalysts, or as pre-catalysts to well defined catalysts, for the hydroboration of a variety of unsaturated substrates by HBpin. Our results strongly suggest that magnesium(i) dimers are not catalysts in these reactions, and that there are many more potential (pre-)catalysts that are generated in these reactions, than have previously been reported.
Hydroborative reduction of amides to amines mediated by La(CH2C6H4NMe2-: O)3
Gong, Mingliang,Guo, Chenjun,Luo, Yunjie,Xie, Hongzhen,Zhang, Fangcao
, p. 779 - 791 (2022/01/22)
The deoxygenative reduction of amides to amines is a great challenge for resonance-stabilized carboxamide moieties, although this synthetic strategy is an attractive approach to access the corresponding amines. La(CH2C6H4NMe2-o)3, a simple and easily accessible lanthanide complex, was found to be highly efficient not only for secondary and tertiary amide reduction, but also for the most challenging primary reduction with pinacolborane. This protocol exhibited good tolerance for many functional groups and heteroatoms, and could be applied to gram-scale synthesis. The active species in this catalytic cycle was likely a lanthanide hydride.
Selective electrocatalytic hydroboration of aryl alkenes
Zhang, Yahui,Zhao, Xiangyu,Bi, Ce,Lu, Wenqi,Song, Mengyuan,Wang, Dongdong,Qing, Guangyan
, p. 1691 - 1699 (2021/03/09)
Organoboron compounds are powerful precursors of value-added organic compounds in synthetic chemistry, and transition metal-catalysed borylation has always been dominant. To avoid toxic reagents and costs associated with metal catalysts, simpler, more eco
Hydroboration of terminal olefins with pinacolborane catalyzed by new 2-iminopyrrolyl iron(ii) complexes
Cruz, Tiago F. C.,Pereira, Laura C. J.,Waerenborgh, Jo?o C.,Veiros, Luís F.,Gomes, Pedro T.
, p. 3347 - 3360 (2019/07/10)
Four paramagnetic 14-electron tetracoordinated Fe(ii) complexes of 5-substituted-2-iminopyrrolyl ligands of the type [Fe{κ2N,N′-5-R-NC4H2-2-C(H)N(2,6-iPr2-C6H3)}(Py)Cl], with R = 2,6-Me2-C6H3 (1a), 2,4,6-iPr3-C6H2 (1b), 2,4,6-Ph3-C6H3 (1c) and CPh3 (1d), were synthesized in moderate yields by reacting the respective 5-substituted-2-iminopyrrolyl potassium salts KLa-d with FeCl2(Py)4 in toluene. Complexes 1a-d were characterized by 1H NMR, FTIR spectroscopies, elemental analysis and by the Evans method, the corresponding effective magnetic moments showing a high-spin electronic nature. X-ray diffraction studies on complexes 1a and 1c showed distorted tetrahedral coordination geometries. Complexes 1a-c, activated with K(HBEt3), were efficient catalyst systems for the hydroboration of several terminal alkenes with pinacolborane in good to high yields (50-90%). This system mainly yielded the respective anti-Markovnikov addition products, except when styrenes were used. A screening of the hydroboration of styrene catalyzed by complexes 1a-c activated with K(HBEt3) showed that the selectivity in the Markovnikov product increased with increasing steric bulkiness of the R group, exhibiting selectivities up to 91%. Additionally, the stoichiometric reaction of complex 1b with K(HBEt3) over 30 minutes yielded the mixture of hydride species 2 and 22 (mixture I). On the other hand, when reacting the same components over 16 h, the Fe(i) complex 3 was also identified in the mixture, in addition to 2 + 22 (mixture II). These mixtures were characterized in solution by the Evans method and in the solid state by elemental analysis, 57Fe M?ssbauer and FTIR spectroscopies, compounds 22 and 3 being also analyzed by X-ray diffraction. These results suggest that the corresponding catalytic cycle follows the borane oxidative addition route to a Fe(i) species.
Deoxygenative Borylation of Secondary and Tertiary Alcohols
Friese, Florian W.,Studer, Armido
supporting information, p. 9561 - 9564 (2019/06/21)
Two different approaches for the deoxygenative radical borylation of secondary and tertiary alcohols are presented. These transformations either proceed through a metal-free silyl-radical-mediated pathway or utilize visible-light photoredox catalysis. Readily available xanthates or methyl oxalates are used as radical precursors. The reactions show broad substrate scope and high functional-group tolerance, and are conducted under mild and practical conditions.
Syntheses, Structures, and Reactivity of NHC Copper(I) Boryl Complexes: A Systematic Study
Kleeberg, Christian,Borner, Corinna
, p. 4136 - 4146 (2018/11/23)
Five novel NHC copper(I) boryl complexes were synthesized by B-B activation via σ-bond metathesis of symmetrical tetraalkoxy and unsymmetrical dialkoxy diamino diborane(4) derivatives. Despite their low stability, the NHC copper boryl complexes were thoroughly characterized spectroscopically and structurally. Variation of the NHC ligand (ItBu or Me2IiPr) as well as of the boryl ligand (Bpin, Bdmab, or BiPrEn) allowed, for the first time systematically, a study in such complexes of the dependence on steric encumbrance. For sterically more demanding ligand combinations, mononuclear linear complexes were obtained, while with less demanding ligand combinations, dimeric dinuclear complexes with two bridging μ-boryl ligands were obtained, exhibiting extremely short Cu···Cu distances (?). The decomposition of all these complexes was found to proceed via a common pathway, leading ultimately to elemental copper, the free NHC ligand, and the respective symmetrical diborane(4) derivative. The rate of decomposition depended strongly on the steric encumbrance of the individual complex. Two apparently low-valent copper clusters were observed and suggested to be relevant species with respect to the reductive decomposition of the copper(I) boryl complexes.
Elusive Phosphine Copper(I) Boryl Complexes: Synthesis, Structures, and Reactivity
Borner, Corinna,Anders, Lisa,Brandhorst, Kai,Kleeberg, Christian
supporting information, p. 4687 - 4690 (2018/02/07)
We report the first isolation of phosphine copper boryl complexes - species pivotal to numerous copper-catalyzed borylation reactions. The reaction of diboron(4) derivatives with copper tert-butoxide complexes of phosphine ligands allows the isolation of the dimeric μ-boryl-bridged Cu(I) complexes [(iPr3P)Cu-Bdmab]2 (4) and [(C6H4(Ph2P)2)Cu-Bpin]2 (6) with Cu···Cu distances of 2.24-2.27 ? (dmab = (NMe)2C6H4, pin = (OCMe2)2)). A slightly more sterically demanding boryl ligand furnishes the unprecedented multinuclear copper boryl complex [(iPr3P)2Cu8(B(iPrEn))3(OtBu)3] (5), a potential intermediate of the decomposition of an initial Cu(I) boryl complex (iPrEn = (NiPr)2C2H4). All complexes were characterized by single-crystal X-ray diffraction, NMR spectroscopy, and elemental analysis. DFT computations support the nature of these unique complexes and give insight into their electronic structures.
Cobalt-Catalyzed Regioselective Borylation of Arenes: N-Heterocyclic Silylene as an Electron Donor in the Metal-Mediated Activation of C?H Bonds
Ren, Hailong,Zhou, Yu-Peng,Bai, Yunping,Cui, Chunming,Driess, Matthias
supporting information, p. 5663 - 5667 (2017/04/28)
C?H Borylation of arenes has been a subject of great interest recently because of its atom-economy and the wide applicability of borylated products in value-added synthesis. A new bis(silylene)cobalt(II) complex bearing a bis(N-heterocyclic silylene)-pyridine pincer ligand (SiNSi) has been synthesized and structurally characterized. It enabled the regioselective catalytic C?H borylation of pyridines, furans, and fluorinated arenes. Notably, it exhibited complementary regioselectivity for the borylation of fluorinated arenes compared to previously known catalytic systems, demonstrating that N-heterocyclic silylene donors have enormous potential in metal-catalyzed catalytic applications.
A method of synthesizing joint boric acidfrequency that ester
-
Paragraph 0060-0065, (2017/03/08)
The invention relates to a method for synthesizing bisdiboron. The method comprises the following steps: preparing a tri-substituted boron midbody from raw materials, namely, nafoxidine and boron tribromide which are easy to obtain from the market, in the presence of an acid-binding agent triethylamine; subsequently reacting with boron tribromide to obtain a bromo-boron midbody; coupling the product in the presence of metal sodium to obtain nafoxidine-substituted coupled boron; finally adding pinacol to react, thereby obtaining a target product, namely, the bisdiboron. The method has the advantages that nafoxidine can be directly recycled, and the triethylamine hydrobromide can be also directly recycled after being simply neutralized and dried. The midbodies obtained in the method disclosed by the invention can be directly used after the solvent is simply distilled, except the compound, the midbodies are all solids when being purified, the operation is easy, the solvent and the reagents can be recycled, the damage to the environment is reduced, and the process can be successfully expanded to be the scale greater than 10kg.
Cobalt-Catalyzed C(sp2)-H Borylation: Mechanistic Insights Inspire Catalyst Design
Obligacion, Jennifer V.,Semproni, Scott P.,Pappas, Iraklis,Chirik, Paul J.
supporting information, p. 10645 - 10653 (2016/09/04)
A comprehensive study into the mechanism of bis(phosphino)pyridine (PNP) cobalt-catalyzed C-H borylation of 2,6-lutidine using B2Pin2 (Pin = pinacolate) has been conducted. The experimentally observed rate law, deuterium kinetic isotope effects, and identification of the catalyst resting state support turnover limiting C-H activation from a fully characterized cobalt(I) boryl intermediate. Monitoring the catalytic reaction as a function of time revealed that borylation of the 4-position of the pincer in the cobalt catalyst was faster than arene borylation. Cyclic voltammetry established the electron withdrawing influence of 4-BPin, which slows the rate of C-H oxidative addition and hence overall catalytic turnover. This mechanistic insight inspired the next generation of 4-substituted PNP cobalt catalysts with electron donating and sterically blocking methyl and pyrrolidinyl substituents that exhibited increased activity for the C-H borylation of unactivated arenes. The rationally designed catalysts promote effective turnover with stoichiometric quantities of arene substrate and B2Pin2. Kinetic studies on the improved catalyst, 4-(H)2BPin, established a change in turnover limiting step from C-H oxidative addition to C-B reductive elimination. The iridium congener of the optimized cobalt catalyst, 6-(H)2BPin, was prepared and crystallographically characterized and proved inactive for C-H borylation, a result of the high kinetic barrier for reductive elimination from octahedral Ir(III) complexes.
