- Nickel-catalyzed Heck reaction of cycloalkenes using aryl sulfonates and pivalates
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Nickel-catalyzed Heck reaction of cycloalkenes delivers unusual conjugated arylated isomers. Nickel(0) catalysts ligated by chelating dialkylphosphines effectively activate not only aryl triflates as electrophiles, but also less reactive aryl mesylates, t
- Zhou, Jianrong Steve,Huang, Xiaolei,Teng, Shenghan,Chi, Yonggui Robin
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supporting information
p. 3933 - 3936
(2021/04/26)
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- Ni-Catalyzed Cross-Coupling of Dimethyl Aryl Amines with Arylboronic Esters under Reductive Conditions
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Herein, we reported a successful Suzuki-Miyaura coupling of dimethyl aryl amines to forge biaryl skeleton via Ni catalysis in the absence of directing groups and preactivation. This transformation proceeded with high efficiency in the presence of magnesium. Preliminary mechanism studies demonstrated dual roles of magnesium: (i) a reductant that reduced Ni(II) species to active Ni(I) catalyst; (ii) a unique promoter that facilitated the Ni(I)/Ni(III) catalytic cycle.
- Cao, Zhi-Chao,Xie, Si-Jun,Fang, Huayi,Shi, Zhang-Jie
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supporting information
p. 13575 - 13579
(2018/10/24)
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- Cross-Coupling of Organolithium with Ethers or Aryl Ammonium Salts by C?O or C?N Bond Cleavage
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Various aryl-, alkenyl-, and/or alkyllithium species reacted smoothly with aryl and/or benzyl ethers with cleavage of the inert C?O bond to afford cross-coupled products, catalyzed by commercially available [Ni(cod)2] (cod=1,5-cyclooctadiene) catalysts with N-heterocyclic carbene (NHC) ligands. Furthermore, the coupling reaction between the aryllithium compounds and aryl ammonium salts proceeded under mild conditions with C?N bond cleavage in the presence of a [Pd(PPh3)2Cl2] catalyst. These methods enable selective sequential functionalizations of arenes having both C?N and C?O bonds in one pot.
- Yang, Ze-Kun,Wang, Dong-Yu,Minami, Hiroki,Ogawa, Hiroyuki,Ozaki, Takashi,Saito, Tatsuo,Miyamoto, Kazunori,Wang, Chao,Uchiyama, Masanobu
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supporting information
p. 15693 - 15699
(2016/10/25)
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- Nickel-catalyzed reductive cleavage of aryl alkyl ethers to arenes in absence of external reductant
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The reductive cleavage of the C-O bonds of aryl ethers has great potential in organic synthesis. Although several catalysts that can promote the reductive cleavage of aryl ethers have been reported, all such systems require the use of an external reductant, e.g., hydrosilane or hydrogen. Here, we report the development of a new nickel-based catalytic system that can cleave the C-O bonds of ethers in the absence of an external reductant. The hydrogen atom required in this new reductive cleavage reaction is provided by the alkoxy group of the substrate, which serves as an internal reductant. The absence of an external reductant enables the unique chemoselectivity, i.e., the selective reduction of an alkoxy group over alkenes and ketones. This journal is
- Tobisu, Mamoru,Morioka, Toshifumi,Ohtsuki, Akimichi,Chatani, Naoto
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p. 3410 - 3414
(2015/05/27)
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- Enantioselective photoredox catalysis enabled by proton-coupled electron transfer: Development of an asymmetric aza-pinacol cyclization
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The first highly enantioselective catalytic protocol for the reductive coupling of ketones and hydrazones is reported. These reactions proceed through neutral ketyl radical intermediates generated via a concerted proton-coupled electron transfer (PCET) event jointly mediated by a chiral phosphoric acid catalyst and the photoredox catalyst Ir(ppy)2(dtbpy)PF6. Remarkably, these neutral ketyl radicals appear to remain H-bonded to the chiral conjugate base of the Bronsted acid during the course of a subsequent C-C bond-forming step, furnishing syn 1,2-amino alcohol derivatives with excellent levels of diastereo- and enantioselectivity. This work provides the first demonstration of the feasibility and potential benefits of concerted PCET activation in asymmetric catalysis.
- Rono, Lydia J.,Yayla, Hatice G.,Wang, David Y.,Armstrong, Michael F.,Knowles, Robert R.
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p. 17735 - 17738
(2014/01/06)
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- Single electron transfer-induced cross-coupling reaction of alkenyl halides with aryl Grignard reagents
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Alkenyl halides were found to undergo coupling with aryl Grignard reagents to give the corresponding styrene derivatives in a stereo-retained manner. The cross-coupling reaction is considered to proceed through a single electron transfer mechanism.
- Shirakawa, Eiji,Watabe, Ryo,Murakami, Takuya,Hayashi, Tamio
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supporting information
p. 5219 - 5221
(2013/06/27)
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- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
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In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
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p. 6014 - 6020
(2013/06/26)
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- Selective arylation at the vinylic site of cyclic olefins
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Cyclic olefins usually give Heck products having an aryl ring residing at the allylic or homoallylic position. We describe herein a new method that allows arylation at the vinylic position of various cyclic olefins.
- Wu, Xiaojin,Zhou, Jianrong
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supporting information
p. 4794 - 4796
(2013/06/05)
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- A peptide-embedded trifluoromethyl ketone catalyst for enantioselective epoxidation
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The development of peptide-based oxidation catalysts that use a transiently generated dioxirane as the chemically active species is reported. The active catalyst is a chiral trifluoromethyl ketone (Tfk) with a pendant carboxylic acid that can be readily incorporated into a peptide. These peptides were capable of epoxidizing alkenes in high yield (up to 89%) and enantiomeric ratios (er) ranging from 69.0:31.0 to 91.0:9.0, depending on the alkene substitution pattern.
- Romney, David K.,Miller, Scott J.
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p. 1138 - 1141
(2012/05/04)
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- Cross-coupling of aryl/alkenyl silyl ethers with grignard reagents through nickel-catalyzed CO bond activation
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CO activation and its application have drawn much attention since oxygen-based electrophiles are easily available, less toxic, and more environmentally benign. This letter presents systematically results on the Ni-catalyzed KumadaTamaoCorriu coupling based on siloxy arenes/alkenes, which provides a new strategy of silyl protection/CC bond formation sequence in organic synthesis.
- Zhao, Fei,Yu, Da-Gang,Zhu, Ru-Yi,Xi, Zhenfeng,Shi, Zhang-Jie
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supporting information; experimental part
p. 1001 - 1003
(2011/12/05)
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- Nickel-catalyzed alkenylative cross-coupling reaction of alkyl sulfides
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A novel cross-coupling reaction of alkyl aryl sulfides with aryl Grignard reagents has been achieved to produce the alkenyl-aryl coupling products in high yields by using catalytic Ni(cod)2 and a bulky N-heterocyclic carbene ligand, SIPr.
- Ishizuka, Kentaro,Seike, Hirofumi,Hatakeyama, Takuji,Nakamura, Masaharu
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supporting information; experimental part
p. 13117 - 13119
(2010/11/05)
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- Arylation and vinylation of alkenes based on unusual sequential semipinacol rearrangement/Grob fragmentation of allylic alcohols
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(Chemical Equation Presented) Alkenes can be stereoselectively arylated and vinylated without transition-metal catalyst under mild conditions through an interesting NBS-promoted semipinacol rearrangement and a subsequent unusual NaOH-mediated Grob fragmentation.
- Yuan, Dao-Yi,Tu, Yong-Qiang,Fan, Chun-An
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p. 7797 - 7799
(2008/12/22)
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- A convenient synthesis of 2-naphthylcyclopentanones and 2-naphthylcyclohexanones from 1-naphthylcycloalkenes
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The oxidation of naphthylcycloalkenes with hydrogen peroxide or MCPBA followed by acid catalyzed rearrangement of diol (epoxide), afforded a series of naphthylcycloalkanones in a very simple manner. The conditions allow preparation of naphthylcycloalkanones on a multigram scale. Georg Thieme Verlag Stuttgart.
- Gora, Maciej,Luczynski, Michal K.,Sepiol, Janusz J.
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p. 1625 - 1630
(2007/10/03)
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- Enantioselective protonation of silyl enol ethers and ketene disilyl acetals with Lewis acid-assisted chiral Bronsted acids: Reaction scope and mechanistic insights
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Enantioselective protonation is a potent and efficient way to construct chiral carbons. Here we report details of the reaction using Lewis acid-assisted chiral Bronsted acids (chiral LBAs). The 1:1 coordinate complex of tin tetrachloride and optically active binaphthol ((R)- or (S)-BINOL) can directly protonate various silyl enol ethers and ketene disilyl acetals to give the corresponding α-aryl ketones and α-arylcarboxylic acids, respectively, with high enantiomeric excesses (up to 98% ee). A catalytic version of enantioselective protonation has also been achieved using stoichiometric amounts of 2,6-dimethylphenol and catalytic amounts of monomethyl ether of optically active BINOL in the presence of tin tetrachloride. This protonation is also effective for producing α-halocarbonyl compounds (up to 91% ee). DFT calculations on the B3LYP/LANL2DZ level show that the conformational structure of the chiral LBA and the orientation of activated proton on (R)-BINOLs are important for understanding the absolute stereochemistry of the products.
- Nakamura, Shingo,Kaneeda, Masanobu,Ishihara, Kazuaki,Yamamoto, Hisashi
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p. 8120 - 8130
(2007/10/03)
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- Nickel-catalyzed cross-couplings of cyclohexenyl phosphate and arylboronic acids
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The Nickel-catalyzed cross-coupling reaction of cyclohexenylphosphate with a variety of arylboronic acids is described here for the first time. This methodology opens the door to other palladium or nickel-catalyzed coupling reactions involving vinyl phosphates.
- Nan, Yang,Yang, Zhen
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p. 3321 - 3324
(2007/10/03)
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- Auxiliary-directed peroxidation of 1,4-dienes
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The addition of singlet oxygen (1O2) to the proximal alkene of auxiliary-tethered 1,4-dienes and the addition of triplet oxygen 3O2) to the proximal position of the corresponding pentadienyl radicals both produce conjugated diene hydroperoxides in moderate to high diastereomeric excess. Negligible stereoselection is observed for additions of 1O2 to the distal alkene of Z,Z-heptadienes due to the lack of control of alkene conformation. Despite evidence for the intermediacy of highly constrained pentadienyl radicals, poor diastereoselection is also observed for distal addition of 3O2. The extent of olefin isomerization observed during radical oxygenations can be correlated with steric constraints on the intermediate pentadienyl and peroxyl radicals and may be relevant to literature reports of olefin isomerization during enzymatic oxygenations of unnatural fatty acids.
- Dussault, Patrick H.,Anderson, Todd A.,Hayden, Michael R.,Koeller, Kevin J.,Jason Niu
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p. 12381 - 12398
(2007/10/03)
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