- Nickel-Catalyzed Borylation of Benzylic Ammonium Salts: Stereospecific Synthesis of Enantioenriched Benzylic Boronates
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We have developed a stereospecific, nickel-catalyzed cross-coupling of secondary benzylic ammonium salts and diboronate esters to deliver highly enantioenriched benzylic boronates. This reaction utilizes amine-derived electrophiles, which are readily available in high enantiopurity, and simple, inexpensive nickel catalysts. This reaction has broad scope, enabling synthesis of a variety of secondary benzylic boronates in good yields and excellent ee's.
- Basch, Corey H.,Cobb, Kelsey M.,Watson, Mary P.
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- Nickel-Catalyzed Enantioselective Hydroboration of Vinylarenes
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The enantioselective hydroboration of vinylarenes catalyzed by a chiral, nonracemic nickel catalyst is presented as a facile method for generating chiral benzylic boronate esters. Various vinylarenes react with bis(pinacolato)diboron (B2pin2) in the presence of MeOH as a hydride source to form chiral boronate esters in up to 92% yield with up to 94% ee. The use of anhydrous Me4NF to activate B2pin2 is crucial for ensuring fast transmetalation to achieve high enantioselectivities.
- Tran, Hai N.,Stanley, Levi M.
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supporting information
p. 395 - 399
(2021/12/27)
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- Chiral 2-imidazoline aniline compound as well as preparation method and application thereof
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The invention provides a chiral 2-imidazoline aniline compound as well as a preparation method and application thereof. The preparation method comprises the following steps: reacting an o-nitrobenzoic acid compound as shown in a formula (1), oxalyl chloride and N, N-dimethylformamide to obtain an o-nitrobenzoyl chloride compound as shown in a formula (7); adding the hydroxyl amide derivative into a mixed solution of an amino alcohol compound as shown in a formula (2) and triethylamine to obtain a hydroxyl amide derivative as shown in a formula (3); reacting with thionyl chloride to obtain a dichloro compound as shown in a formula (4); then adding triethylamine and primary amine R2NH2 to prepare a nitroimidazoline derivative; and finally, reducing to obtain the chiral 2-imidazoline aniline compound as shown in a formula (6). The chiral 2-imidazoline aniline compound is easy to prepare, the raw materials are cheap and easy to obtain, the preparation method is simple, and the synthesized chiral ligand containing the 2-imidazoline aniline fragment can be used as a catalyst for catalyzing asymmetric hydroboration reaction of cobalt-catalyzed olefin and asymmetric hydroamination reaction of cobalt-catalyzed non-activated terminal olefin.
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Paragraph 0147-0152; 0161-0162
(2021/07/14)
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- Cobalt-Catalyzed Asymmetric Markovnikov Hydroboration of Styrenes
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A cobalt-catalyzed asymmetric hydroboration of styrenes using an imidazoline phenyl picoliamide (ImPPA) ligand was first reported to deliver the valuable chiral secondary organoboronates with good functional tolerance and high enantioselectivity (up to >9
- Chen, Xu,Cheng, Zhaoyang,Lu, Zhan
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p. 4025 - 4029
(2019/04/25)
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- Chiral quinoline amine compound and preparation method and application thereof
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The invention discloses a chiral quinoline amine compound shown in a formula (1), and discloses a simple preparation method convenient to implement. The quinoline amine shown in the formula (1) can beused for preparing a chiral organic boron ester compound. A chiral oxazoline or imidazoline base quinoline amine compound and a transition metal MY'n in-situ complex can be adopted as a homogeneous catalyst, the catalyst is subjected to asymmetry hydroboration addition on carbon-carbon atom double bonds of the prochirality organic compound to be used for preparing the chiral organic boron compound, and the prochirality unsaturated compound for optimizing the asymmetric boron hydrogen effect is a styrene compound. The prepared chiral organic boron ester compound is an important organic synthesis midbody and is particularly applied to the production aspect of medicine preparations, spice, fumet and agricultural chemicals.
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Paragraph 0178; 0179; 0180
(2018/11/22)
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- Mechanistic Studies of Copper-Catalyzed Asymmetric Hydroboration of Alkenes
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Mechanistic studies of the copper-catalyzed asymmetric hydroboration of vinylarenes and internal alkenes are reported. Catalytic systems with both DTBM-SEGPHOS and SEGPHOS as the ligands have been investigated. With DTBM-SEGPHOS as the ligand, the resting state of the catalyst, which is also a catalytic intermediate, for hydroboration of 4-fluorostyrene is a phenethylcopper(I) complex ligated by the bisphosphine. This complex was fully characterized by NMR spectroscopy and X-ray crystallography. The turnover-limiting step in the catalytic cycle for the reaction of vinylarenes is the borylation of this phenethylcopper complex with pinacolborane (HBpin) to form the boronate ester product and a copper hydride. Experiments showed that the borylation occurs with retention of configuration at the benzylic position. β-Hydrogen elimination and insertion of the alkene to reform this phenethylcopper complex is reversible in the absence of HBpin but is irreversible during the catalytic process because reaction with HBpin is faster than β-hydrogen elimination of the phenethylcopper complex. Studies on the hydroboration of a representative internal alkene, trans-3-hexenyl 2,4,6-trichlorobenzoate, which undergoes enantio- and regioselective addition of HBpin catalyzed by DTBM-SEGPHOS, KOtBu, and CuCl, also was conducted, and these studies revealed that a DTBM-SEGPHOS-ligated copper(I) dihydridoborate complex is the resting state of the catalyst in this case. The turnover-limiting step in the catalytic cycle for hydroboration of the internal alkene is insertion of the alkene into a copper(I) hydride formed by reversible dissociation of HBpin from the copper dihydridoborate species. With SEGPHOS as the ligand, a dimeric copper hydride was observed as the dominant species during the hydroboration of 4-fluorostyrene, and this complex is not catalytically competent. DFT calculations provide a view into the origins of regio- and enantioselectivity of the catalytic process and indicate that the charge on the copper-bound carbon and delocalization of charge onto the aryl ring control the rate of the alkene insertion and the regioselectivity of the catalytic reactions of vinylarenes.
- Xi, Yumeng,Hartwig, John F.
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supporting information
p. 12758 - 12772
(2017/09/25)
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