- Dihalogenation of Alkenes Using Combinations of N-Halosuccinimides and Alkali Metal Halides
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A simple, efficient and eco-friendly method for the vicinal dihalogenation of alkenes is described. The reaction is performed with a combination of a N-halosuccinimide and an alkali metal halide using environmentally benign solvents such as acetic acid an
- Barrio, Pablo,García-Pedrero, Olaya,López-Matanza, Pablo,Rodríguez, Félix,Rubio-Presa, Rubén
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supporting information
p. 4762 - 4766
(2021/09/10)
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- Electrochemical Synthesis of O-Phthalimide Oximes from α-Azido Styrenes via Radical Sequence: Generation, Addition and Recombination of Imide-N-Oxyl and Iminyl Radicals with C?O/N?O Bonds Formation
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Electrochemically induced radical-initiated reaction of vinyl azides with N-hydroxyphthalimide resulting O-phthalimide oximes with challenging for organic chemistry N?O-N fragment has been discovered. The developed approach introduces in synthesis electrochemically generated O-centered imide-N-oxyl radicals as the coupling components. Sequential formation of C?O and N?O bonds was achieved via generation and selective addition of imide-N-oxyl radicals, followed by recombination with iminyl radicals. A wide range of O-phthalimide oximes was obtained with the yields up to 84percent. (Figure presented.).
- Paveliev, Stanislav A.,Churakov, Artem I.,Alimkhanova, Liliya S.,Segida, Oleg O.,Nikishin, Gennady I.,Terent'ev, Alexander O.
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supporting information
p. 3864 - 3871
(2020/07/30)
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- Asymmetric Nazarov Cyclizations of Unactivated Dienones by Hydrogen-Bond-Donor/Lewis Acid Co–Catalyzed, Enantioselective Proton-Transfer
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We report an enantioselective Nazarov cyclization catalyzed by chiral hydrogen-bond-donors in concert with silyl Lewis acids. The developed transformation provides access to tri-substituted cyclopentenones in high levels of enantioselectivity (up to 95% e.e.) from a variety of simple unactivated dienones. Kinetic and mechanistic studies are consistent with a reversible 4π-electrocyclization C?C bond-forming step followed by rate- and enantio-determining proton-transfer as the mode of catalysis. (Figure presented.).
- Metternich, Jan B.,Reiterer, Martin,Jacobsen, Eric N.
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supporting information
p. 4092 - 4097
(2020/09/01)
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- Rh(III)-Catalyzed C-H Activation-Initiated Directed Cyclopropanation of Allylic Alcohols
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We have developed a Rh(III)-catalyzed diastereoselective [2+1] annulation onto allylic alcohols initiated by alkenyl C-H activation of N-enoxyphthalimides to furnish substituted cyclopropyl-ketones. Notably, the traceless oxyphthalimide handle serves three functions: directing C-H activation, oxidation of Rh(III), and, collectively with the allylic alcohol, in directing cyclopropanation to control diastereoselectivity. Allylic alcohols are shown to be highly reactive olefin coupling partners leading to a directed diastereoselective cyclopropanation reaction, providing products not accessible by other routes.
- Phipps, Erik J. T.,Rovis, Tomislav
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supporting information
(2019/05/06)
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- Rh(III)-Catalyzed C-H Activation-Initiated Directed Cyclopropanation of Allylic Alcohols
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We have developed a Rh(III)-catalyzed diastereoselective [2+1] annulation onto allylic alcohols initiated by alkenyl C-H activation of N-enoxyphthalimides to furnish substituted cyclopropyl-ketones. Notably, the traceless oxyphthalimide handle serves three functions: Directing C-H activation, oxidation of Rh(III), and, collectively with the allylic alcohol, in directing cyclopropanation to control diastereoselectivity. Allylic alcohols are shown to be highly reactive olefin coupling partners leading to a directed diastereoselective cyclopropanation reaction, providing products not accessible by other routes.
- Phipps, Erik J.T.,Rovis, Tomislav
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supporting information
p. 6807 - 6811
(2019/05/10)
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- Visible-Light-Induced Regioselective C(sp3)-H Acyloxylation of Aryl-2 H-azirines with (Diacetoxy)iodobenzene
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A visible-light-promoted regioselective coupling of C(sp3)-H of aryl-2H-azirine and (diacetoxy)iodobenzene has been reported. Rose Bengal as an organophotoredox catalyst has been used in this reaction. The reaction proceeds under aerobic condition at room temperature. A variety of aryl-2H-azirines gives the corresponding acyloxylated azirines under this reaction conditions. The reaction goes through a radical pathway. The protocol is also applicable on gram-scale synthesis.
- De, Aramita,Santra, Sougata,Hajra, Alakananda,Zyryanov, Grigory V.,Majee, Adinath
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supporting information
p. 11735 - 11740
(2019/10/02)
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- Rhodium(III)-Catalyzed Cyclopropanation of Unactivated Olefins Initiated by C-H Activation
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We have developed a rhodium(III)-catalyzed cyclopropanation of unactivated olefins initiated by an alkenyl C-H activation. A variety of 1,1-disubstituted olefins undergo efficient cyclopropanation with a slight excess of alkene stoichiometry. A series of mechanistic interrogations implicate a metal carbene as an intermediate.
- Phipps, Erik J. T.,Piou, Tiffany,Rovis, Tomislav
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supporting information
p. 1787 - 1790
(2019/09/09)
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- Intermolecular Carboamination of Unactivated Alkenes
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Herein, we report the first example of group transfer radical addition of O-vinylhydroxylamine derivatives onto unactivated alkenes. By utilizing O-vinylhydroxylamine derivatives as both the N- and C-donors, this reaction enables intermolecular carboamination of unactivated alkenes in an atom economical fashion. As the process is initiated through N-radical addition followed by C-transfer, linear carboamination products are afforded. This differs from canonical radical carbofunctionalization of olefins, which typically favors branched product owing to initiation by C-radical addition.
- Zhang, Yu,Liu, Haidong,Tang, Luning,Tang, Hai-Jun,Wang, Lu,Zhu, Chuan,Feng, Chao
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supporting information
p. 10695 - 10699
(2018/09/06)
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- Visible-Light Photoredox Catalyzed Three-Component Cyclization of 2H-Azirines, Alkynyl Bromides, and Molecular Oxygen to Oxazole Skeleton
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A novel three-component cyclization of 2H-azirines, alkynyl bromides, and molecular oxygen under visible-light photoredox catalysis at room temperature has been developed, which provides a direct approach to a wide range of substituted oxazoles in moderate to good yields.
- Chen, Lili,Li, Hongji,Li, Pinhua,Wang, Lei
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supporting information
p. 3646 - 3649
(2016/08/16)
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- Efficient bromination of olefins, alkynes, and ketones with dimethyl sulfoxide and hydrobromic acid
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The oxidative bromination of olefins, alkynes, and ketones has been developed with HBr as the brominating reagent and DMSO as the mild oxidant. The simple conditions, high bromide-atom-economy, as well as easy accessibility and low cost of DMSO and HBr make the present strategy prospective for the synthesis of dibrominated alkanes, dibrominated alkenes and α-bromoketones.
- Song, Song,Li, Xinwei,Sun, Xiang,Yuan, Yizhi,Jiao, Ning
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supporting information
p. 3285 - 3289
(2015/06/25)
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- Rh(III)-catalyzed cyclopropanation initiated by C-H activation: Ligand development enables a diastereoselective [2 + 1] annulation of N-enoxyphthalimides and alkenes
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N-Enoxyphthalimides undergo a Rh(III)-catalyzed C-H activation initiated cyclopropanation of electron deficient alkenes. The reaction is proposed to proceed via a directed activation of the olefinic C-H bond followed by two migratory insertions, first across the electron-deficient alkene and then by cyclization back onto the enol moiety. A newly designed isopropylcyclopentadienyl ligand drastically improves yield and diastereoselectivity.
- Piou, Tiffany,Rovis, Tomislav
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supporting information
p. 11292 - 11295
(2014/09/17)
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- A bimetallic palladium(II) catalyzed synthesis of 1,2-dibromo compounds
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A bimetallic palladium(II) catalyst containing a triketone ligand and a bridging dinitrogen ligand oxidizes aromatic and cyclic aliphatic olefins in bromide-containing aqueous-THF to 1,2-dibromo compounds and bromohydrins. With aromatic olefins, the 1,2-dibromo products were obtained in a 70-80% yield and the bromohydrins in a 10-15% yield; this observation is opposition to that obtained in chloride containing medium where the chlorohydrin product predominates. The oxidation of 2,3-dihydrofuran gave trans-2,3- dibromotetrahydrofuran, 3-oxotetrahydrofuran, and 3-bromo-2- hydroxytetrahydrofuran in relative yields of 75%, 15%, and 10%, respectively. On the other hand, the oxidation of cyclopentene and cyclohexene affords only trans-1,2-dibromo products in about 90% yield. The stereochemistry is consistent with an anti-at-tack of bromide followed by decomposition involving attack of bromide from the coordination sphere of the Pd(II). The procedure outlined here is a convenient method for the one step synthesis of 1,2-dibromides.
- Qaseer
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