- Chemoselective Cross-Coupling of gem-Borazirconocene Alkanes with Aryl Halides
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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.
- Bai, Songlin,Gao, Yadong,Jiang, Chao,Qi, Xiangbing,Yang, Chao
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supporting information
p. 11506 - 11513
(2020/07/14)
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- Metal Cu (I) complex, preparation method and application thereof
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The invention provides a metal Cu (I) complex, a preparation method and an application thereof. Tri-tert-butylphosphine imine anions and n-heterocyclic carbine are used as the ligands and coordinated with metal Cu (I) to synthesize the metal Cu (I) comple
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Paragraph 0075; 0076
(2017/07/11)
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- Multikilogram-scale synthesis of a chiral cyclopropanol and an investigation of the safe use of lithium acetylide-ethylene diamine complex
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A six-step route starting from a readily available vinyl boronate was identified to produce an enantioenriched cyclopropanol in an overall 16% yield. Key steps involve the use of lithium acetylide-ethylene diamine complex 5 and an enzymatic resolution of a racemic cyclopropanol acetate. Process safety considerations surrounding the use of 5 were examined, and an improved procedure is described which was safely demonstrated at multikilogram scale.
- Bassan, Ephraim M.,Baxter, Carl A.,Beutner, Gregory L.,Emerson, Khateeta M.,Fleitz, Fred J.,Johnson, Simon,Keen, Stephen,Kim, Mary M.,Kuethe, Jeffrey T.,Leonard, William R.,Mullens, Peter R.,Muzzio, Daniel J.,Roberge, Christopher,Yasuda, Nobuyoshi
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scheme or table
p. 87 - 95
(2012/05/31)
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- 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
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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.
- Jang, Hwanjong,Zhugralin, Adil R.,Lee, Yunmi,Hoveyda, Amir H.
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supporting information; experimental part
p. 7859 - 7871
(2011/06/27)
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- Vicinal diboronates in high enantiomeric purity through tandem site-selective NHC-Cu-catalyzed boron-copper additions to terminal alkynes
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(Chemical Equation Presented) A Cu-catalyzed protocol for conversion of terminal alkynes to enantiomerically enriched diboronates is reported. In a single vessel, a site-selective hydroboration of an alkyne leads to the corresponding terminal vinylboronat
- Lee, Yunmi,Jang, Hwanjong,Hoveyda, Amir H.
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p. 18234 - 18235
(2010/04/25)
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- Highly stereoselective synthesis of cis-alkenyl pinacolboronates and potassium cis-alkenyltrifluoroborates via a hydroboration/protodeboronation approach
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(Chemical Equation Presented) A number of alkynyl pinacolboronates bearing various functional groups were synthesized according to literature methods. These were then stereoselectively reduced to the ds-alkenyl pinacolboronates via hydroboration with dicyclohexylborane followed by chemoselective protodeboronation using acetic acid. Treatment with potassium hydrogen fluoride smoothly converted these to the corresponding potassium organotrifluoroborates.
- Molander, Gary A.,Ellis, Noel M.
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p. 6841 - 6844
(2008/12/22)
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- Preparation of polyfunctional diorganomercurials and their transmetallation to diorganozincs. Applications to the preparation of optically active secondary alcohols
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Two new methods of preparation of functionalized diorganomercurials have been developed.The first method involves a substitution reaction of (ICH2)2Hg with zinc-copper reagents FG-RCu(CN)ZnI in THF/DMF at -60 deg C.Functional groups such as an ester, nitrile, ketone, phosphonate, halide, and boronic ester are tolerated in this reaction.The second method involves a reductive transmetallation between polyfunctional organozinc halides and mercurous chloride (Hg2Cl2).This very convenient procedure provides a rapid route to various functionalized diorganomercurials in good yields (61-89percent yield).The synthetic utility of these mercury organometallics is demonstrated.Their transmetallation with zinc dust (toluene, 80 deg C, 3-5 h) affords dialkylzincs which add enantioselectively to aldehydes in the presence of a catalytic amount (20 molpercent) of the norephedrine derivative 13.This transmetallation can also be used to prepare stereoselectively (E)-alkenylzinc halides (> 98percent E).Addition of Cl(H)ZrCp2 to (E)-5-chloropentenylzinc bromide in CH2Cl2 (25 deg C, 1 min) affords a 1,1-bimetallic of zinc and zirconium Cl(CH2)4CH(ZnBr)ZrCp2(Cl) which reacts stereoselectively with an aldehyde providing the (E)-disubstituted olefin (49percent yield; 100percent E).
- Rozema, Michael J.,Rajagopal, Duddu,Tucker, Charles E.,Knochel, Paul
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