170942-79-7Relevant academic research and scientific papers
Flexible Coordination of N,P-Donor Ligands in Aluminum Dimethyl and Dihydride Complexes
Falconer, Rosalyn L.,Nichol, Gary S.,Cowley, Michael J.
, p. 11439 - 11448 (2019)
Aluminum hydrides, once a simple class of stoichiometric reductants, are now emerging as powerful catalysts for organic transformations such as the hydroboration or hydrogenation of unsaturated bonds. The coordination chemistry of aluminum hydrides supported by P donors is relatively underexplored. Here, we report aluminum dihydride and dimethyl complexes supported by amidophosphine ligands and study their coordination behavior in solution and in the solid state. All complexes exist as κ2-N,P complexes in the solid state. However, we find that for amidophosphine ligands bearing bulky aminophosphine donors, aluminum dihydride and dimethyl complexes undergo a "ligand-slip" rearrangement in solution to generate κ2-N,N complexes. Thus, importantly for catalytic activity, we find that the coordination behavior of the P donor can be modulated by controlling its steric bulk. We show that the reported aluminum hydrides catalyze the hydroboration of alkynes by HBPin and that the variable coordination mode exhibited by the amidophosphine ligand modulates the catalytic activity.
Origins of Internal Regioselectivity in Copper-Catalyzed Borylation of Terminal Alkynes
Tsushima, Takumi,Tanaka, Hideya,Nakanishi, Kazuki,Nakamoto, Masaaki,Yoshida, Hiroto
, p. 14381 - 14387 (2021/12/01)
Installation of a boron functionality into a more substituted carbon of terminal alkynes has been a challenging issue in chemical synthesis, since inherently Lewis acidic boron moieties, in principle, favor their attachment to a terminal carbon. Herein, we report on the highly internal-selective borylation of terminal alkynes under copper catalysis, wherein diminishment of boron-Lewis acidity and ligand-derived steric bulk around a copper center are the key to the success. In particular, the use of an anthranilamide-substituted boron moiety [B(aam)] is of high synthetic significance, because its properly diminished Lewis acidity enabled the internal regioselectivity and the Suzuki-Miyaura cross-coupling activity to be compatibly achieved. This method provided a direct and universal approach to variously substituted branched alkenylboron compounds, regardless of electronic and steric properties of a substituent on terminal alkynes.
Pyridylpyrrolido ligand in Ge(ii) and Sn(ii) chemistry: Synthesis, reactivity and catalytic application
Pahar, Sanjukta,Sen, Sakya S.,Sharma, Vishal,Tothadi, Srinu
supporting information, p. 16678 - 16684 (2021/12/07)
In our previous communication, we have reported the synthesis of a new chlorogermylene (B) featuring a pyridylpyrrolido ligand. This study details the preparation of a series of new germylenes and stannylenes starting from B. A transmetallation reaction between B and SnCl2 led to the analogous chlorostannylene (1) with the simultaneous elimination of GeCl2. This is a very unusual example of transmetallation between two elements of the same group. The preparation of 1via lithiation led to the formation of 2 as a side product, where the ortho C-H bond of the pyridine ring was activated and functionalized with a nBu moiety. Subsequently, B and 1 were used as precursors to generate germylene (4) and stannylene (5) featuring tris(trimethylsilyl)silyl (hypersilyl) moieties. We also prepared tetrafluoropyridyl germylene (6) by reacting 4 with C5F5N with the simultaneous elimination of (Me3Si)3SiF by utilizing the fluoride affinity of the silicon atom. As there is scarcity of Sn(ii) compounds as single-site catalysts, we investigated 5 as a catalyst towards the hydroboration of aldehydes, ketones, alkenes and alkynes. All the compounds have been characterized by single-crystal X-ray diffraction and by state of the art spectroscopic studies.
Chemoselective Cross-Coupling of gem-Borazirconocene Alkanes with Aryl Halides
Bai, Songlin,Gao, Yadong,Jiang, Chao,Qi, Xiangbing,Yang, Chao
supporting information, p. 11506 - 11513 (2020/07/14)
The direct and chemoselective conversion of the carbon-metal bond of gem-dimetallic reagents enables rapid and sequential formation of multiple carbon-carbon and carbon-heteroatom bonds, thus representing a powerful method for efficiently increasing structural complexity. Herein, we report a visible-light-induced, nickel-catalyzed, chemoselective cross-coupling reaction between gem-borazirconocene alkanes and diverse aryl halides, affording a wide range of alkyl Bpin derivatives in high yields with excellent regioselectivity. This practical method features attractively simple reaction conditions and a broad substrate scope. Additionally, we systematically investigated a Bpin-directed chain walking process underlying the regioselectivity of alkylzirconocenes, thus uncovering the mechanism of the remote functionalization of internal olefins achieved with our method. Finally, DFT calculations indicate that the high regioselectivity of this reaction originates from the directing effect of the Bpin group.
H2-Acceptorless Dehydrogenative Boration and Transfer Boration of Alkenes Enabled by Zirconium Catalyst
Shi, Xiaonan,Li, Sida,Wu, Lipeng
supporting information, p. 16167 - 16171 (2019/11/03)
The first example of an efficient and direct dehydrogenative boration of alkenes for vinyl boronate ester synthesis was achieved using a zirconium catalyst. Our methodology avoids using precious transition metals, additional hydrogen acceptors, high temperatures, and long reaction times, which were required to overcome the reducing ability of borane, to give alkyl boronate esters. Detailed mechanistic studies revealed a reversible reaction pathway and further suggested applying the zirconium complex as a “shuttle catalyst” for transfer boration, which thus sidesteps the use of relatively sensitive borane.
Synthetic method of alkenyl borate compound
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Paragraph 0052, (2019/12/02)
The invention relates to a synthesis method of an alkenyl borate compound, which comprises the following steps: dissolving an olefin compound and a borane compound in a solvent, adding a zirconium catalyst, reacting at 0-150 DEG C for 5 minutes to 8 hours
Copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium
Yao, Zi-Jian,Hong, Shibin,Zhang, Wei,Liu, Mengyan,Deng, Wei
supporting information, p. 910 - 913 (2016/02/05)
A mild and environment-friendly copper-catalyzed hydroboration of terminal alkynes in aqueous medium was reported. Regioselectivity control was achieved in the presence of cyclodextrin-bispyridine ligand (CD-1). This protocol was successfully applied to inactivated terminal alkynes. Moreover, the ligand was recovered and reused without any loss of activity over five cycles.
Superparamagnetic copper ferrite nanoparticles catalyzed aerobic, ligand-Free, regioselective hydroboration of alkynes: Influence of synergistic effect
Mohan, Balaji,Park, Kang Hyun
, p. 78 - 84 (2016/04/05)
We discovered a general and comprehensive approach for the regioselective hydroboration of terminal and internal alkynes to synthesize vinylboronates using inexpensive and magnetically separable copper ferrite nanoparticles at low catalyst loading using Bis(pinacolato)diboron in the absence of ligand and additives, under mild and greener conditions. A diverse range of functional groups was tolerated in the reaction, including allene and enones, and the corresponding boronates were obtained in high yields under air. Moreover, the assynthesized alkenylboronates were used as precursors to prepare wide variety of vinylorgano chalcogenides regioselectively, in high yields. The present protocol enable the conversion of Csp-H bonds to make Csp2-B bonds via activation of B-B bond, followed by formation of Csp2-Se (Te or S) bonds via activation of Se (Te or S)- Se (Te or S) bonds in a regioselective manner. Deuterium isotope labeling studies showed that the proton source of vinyl boronate stem from the solvent employed.
CuII-catalyzed regioselective borylation of alkynes and alkenes
Liu, Shiwen,Zeng, Xiaojun,Xu, Bo
supporting information, p. 3706 - 3710 (2016/07/26)
We developed a regioselective borylation of alkynes and alkenes protocol based on air-stable CuII/multi-dentate ligand system. Our catalytic system gives exclusive β-borylation products for most substrates in excellent chemical yields. We propo
Highly selective methods for synthesis of internal (α-) vinylboronates through efficient NHC-Cu-catalyzed hydroboration of terminal alkynes. Utility in chemical synthesis and mechanistic basis for selectivity
Jang, Hwanjong,Zhugralin, Adil R.,Lee, Yunmi,Hoveyda, Amir H.
supporting information; experimental part, p. 7859 - 7871 (2011/06/27)
Cu-catalyzed methods for site-selective hydroboration of terminal alkynes, where the internal or α-vinylboronate is generated predominantly (up to >98%) are presented. Reactions are catalyzed by 1-5 mol % of N-heterocyclic carbene (NHC) complexes of copper, easily prepared from N-aryl-substituted commercially available imidazolinium salts, and proceed in the presence of commercially available bis(pinacolato)diboron [B2(pin)2] and 1.1 equiv of MeOH at -50 to -15 °C in 3-24 h. Propargyl alcohol and amine and the derived benzyl, tert-butyl, or silyl ethers as well as various amides are particularly effective substrates; also suitable are a wide range of aryl-substituted terminal alkynes, where higher α-selectivity is achieved with substrates that bear an electron-withdrawing substituent. α-Selective Cu-catalyzed hydroborations are amenable to gram-scale procedures (1 mol % catalyst loading). Mechanistic studies are presented, indicating that α selectivity arises from the structural and electronic attributes of the NHC ligands and the alkyne substrates. Consistent with suggested hypotheses, catalytic reactions with a Cu complex, derived from an N-adamantyl-substituted imidazolinium salt, afford high β selectivity with the same class of substrates and under similar conditions.
