- Formal Allylation and Enantioselective Cyclopropanation of Donor/Acceptor Rhodium(II) Azavinyl Carbenes
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A highly efficient formal allylation of dihydronaphthotriazoles with alkenes under rhodium(II) catalysis is reported. Various allyl dihydronaphthalene derivatives were furnished via rhodium(II) azavinyl carbenes with moderate to good yields and excellent chemoselectivity. When monosubstituted alkenes are used, cyclopropanation occurs and good to excellent enantioselectivities have been achieved. Particularly noteworthy is the allylic C(sp2)-H activation instead of traditional C(sp3)-H activation in the formal allylation process.
- Liu, Zhili,Chen, Lianfen,Zhu, Dong,Zhu, Shifa
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supporting information
p. 1275 - 1279
(2021/02/20)
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- Consecutive borylcupration/C-C coupling of ?-alkenyl aldehydes towards diastereoselective 2-(borylmethyl)cycloalkanols
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Copper(i) catalyzes the borylative cyclization of ?-alkenyl aldehydes through chemo- and regioselective addition of Cu-B to C?C and concomitant intramolecular 1,2-addition of Cu-C on C?O. The products are formed in an exclusive diastereoselective manner and computational analysis identifies the key points for the observed chemo- and diastereoselectivity.
- Carbó, Jorge J.,Fernández, Elena,Maza, Ricardo J.,Royes, Jordi
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supporting information
p. 5973 - 5976
(2020/06/05)
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- Cu/Ni-Catalyzed Cyanomethylation of Alkenes with Acetonitrile for the Synthesis of β,γ-Unsaturated Nitriles
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We have developed a protocol for the Cu/Ni-catalyzed cyanomethylation of alkenes with acetonitrile for the synthesis of β,γ-unsaturated nitriles. This is the first example of a direct coupling of the alkene sp2 C - H bond and the acetonitrile sp3 C - H bond for the preparation of β,γ-unsaturated nitriles. Acetonitrile, an inexpensive and stable solvent, is demonstrated to be a useful cyanomethyl source. The combination of copper and nickel catalysts resulted in a high reaction efficiency.
- Jian, Hong,Shen, Zengming,Zhang, Saisai
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p. 6143 - 6150
(2020/05/22)
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- Additions of Aldehyde-Derived Radicals and Nucleophilic N-Alkylindoles to Styrenes by Photoredox Catalysis
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The consecutive addition of acyl radicals and N-alkylindole nucleophiles to styrenes was established, as well as some additional radical-nucleophile combinations. Both aryl and aliphatic aldehydes give reasonable yields. The reaction proceeds best for α-substituted styrenes, effectively creating a quaternary all-carbon center. Some iridium-based photoredox systems are catalytically active; furthermore, a base is needed in this transformation. Radicals are formed by reductive perester cleavage and hydrogen atom transfer.
- Klussmann, Martin,Lux, Marcel
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supporting information
(2020/04/30)
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- Synthesis of Tertiary Benzylic Nitriles via Nickel-Catalyzed Markovnikov Hydrocyanation of α-Substituted Styrenes
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The Markovnikov hydrocyanation of α-substituted styrenes enables the synthesis of tertiary benzylic nitriles under nickel catalysis. The Lewis-acid-free transformation features an unprecedented functional groups tolerance, including the-OH and-NH2 groups. A broad range of tertiary benzylic nitriles were obtained in good to excellent yields. In addition, an asymmetric version of this reaction was preliminarily investigated.
- Xing, Yidan,Yu, Rongrong,Fang, Xianjie
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supporting information
p. 1008 - 1012
(2020/02/04)
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- Regioselective Copper-Catalyzed Oxidative Coupling of α-Alkylated Styrenes with Tertiary Alkyl Radicals
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A radical-mediated oxidative cross-coupling of readily accessible α-alkylated styrenes with 1,3-dicarbonyl compounds utilizing a combination of Cu(OAc)2 and air as a catalytic system is described. Rather than requiring α-halocarbonyl compounds, this efficient approach enables direct installation of tertiary functionalized alkyl motifs to olefins with simple carbonyl derivatives. The novel protocol is characterized with high allylic selectivities via a competing β-H elimination. Both radical-clock and -trapping experiments provided clear-cut evidence for the intermediacy of an α-keto carbon-centered radical.
- Wang, Cong,Liu, Rui-Hua,Tian, Ming-Qing,Hu, Xu-Hong,Loh, Teck-Peng
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supporting information
p. 4032 - 4035
(2018/07/15)
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- Enantioselective synthesis of cyclobutenes by intermolecular [2+2] cycloaddition with non-c2 symmetric digold catalysts
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The enantioselective intermolecular gold-(I)-catalyzed [2+2] cycloaddition of terminal alkynes and alkenes has been achieved using non-C2-chiral Josiphos digold(I) complexes as catalysts, by the formation of the monocationic complex. This new approach has been applied to the enantioselective total synthesis of rumphellaone A.
- García-Morales, Cristina,Ranieri, Beatrice,Escofet, Imma,López-Suarez, Laura,Obradors, Carla,Konovalov, Andrey I.,Echavarren, Antonio M.
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supporting information
p. 13628 - 13631
(2017/11/06)
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- Chelation versus Non-Chelation Control in the Stereoselective Alkenyl sp2 C?H Bond Functionalization Reaction
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A hydroxy group chelation-assisted stereospecific oxidative cross-coupling reaction between alkenes was developed under mild reaction conditions. In the presence of palladium catalyst, the alkenes tethered with hydroxy functionality can couple efficiently with electron-deficient alkenes to form the corresponding multi-substituted olefin products. The hydroxy group on the substrate could play dual roles in reaction, acting as the directing group for alkenyl C?H bond activation and controlling the stereoselectivity of the products.
- Liang, Qiu-Ju,Yang, Chao,Meng, Fei-Fan,Jiang, Bing,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 5091 - 5095
(2017/04/24)
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- Trifluoromethylation of aromatic alkenes by visible-light-driven photoredox catalysis: Direct conversion of alkenes to 3-trifluoromethyl-1-propenyl and 1,3-bis(trifluoromethyl)-1-propenyl derivatives
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Photoredox-catalyzed trifluoromethylation of alkenes using Umemoto's reagent as a CF3 source under visible light irradiation has been developed. A Ru photocatalyst, [Ru(bpy)3](PF6)2 (bpy = 2,2′-bipyridine), is useful for the present trifluoromethylation and preferable formation of 3-trifluoromethyl-1-propenyl derivatives is observed. Use of an excess amount of Umemoto's reagent readily induces double trifluoromethylation of electron-rich alkenes, resulting in 1,3-bis(trifluoromethyl)-1-propenyl skeleton.
- Asano, Masashi,Tomita, Ren,Koike, Takashi,Akita, Munetaka
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supporting information
p. 83 - 88
(2015/11/10)
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- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
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Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
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supporting information
p. 10545 - 10549
(2015/09/02)
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- Highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes
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Building the building blocks: A highly enantioselective hydrogenation of ?-aryl-?-alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomerically pure nitroalkanes 2, which are versatile precursors for chemical synthesis.
- Li, Shengkun,Huang, Kexuan,Cao, Bonan,Zhang, Jiwen,Wu, Wenjun,Zhang, Xumu
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supporting information; experimental part
p. 8573 - 8576
(2012/09/10)
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- Alkylalumination of arylacetylene catalyzed by zirconocene catalysts supported on solid materials
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Zirconocene dichloride (Cp2ZrCl2) supported on montmorillonite K-10, which has previously been shown to be an efficient catalytic system for olefin polymerization, was found to be comparable to the highly activated homogeneous combin
- Takagi, Ryukichi,Igata, Nao,Yamamoto, Kazuhiro,Kojima, Satoshi
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experimental part
p. 71 - 76
(2010/10/04)
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- Improved preparative route toward 3-arylcyclopropenes
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A convenient preparative protocol for the synthesis of various 3-arylcyclopropenes in a multigram scale is disclosed. Optimization of the reaction conditions and isolation procedures allowed for significant improvement of the chemical yields of these strained products. The described protocol was used for efficient preparation of a series of 3-methyl-3-arylcyclopropenes possessing different substituents in the aromatic ring. The effect of substitution in the aryl group on the stability of 3-arylcyclopropenes, as well as the corresponding precursors, is discussed.
- Sherrill, William M.,Kim, Ryan,Rubin, Michael
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p. 8610 - 8617
(2008/12/21)
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- Suzuki cross-coupling reactions between alkenylboronic acids and aryl bromides catalysed by a tetraphosphane-palladium catalyst
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A range of alkenylboronic acids undergo Suzuki cross-coupling with aryl bromides in good yields in the presence of [PdCl(C3H 5)]2/cis,cis,cis-1,2,3,4-tetrakis[(diphenylphosphanyl) methyl]cyclopentane as a catalyst. A wide variety of 1-arylprop-1-enes, 2-arylprop-1-enes, 2-arylbut-1-enes and 1,1-diarylethylene or styrene derivatives have been prepared. Moreover, the reaction tolerates several functions, such as acetyl, formyl, nitrile or nitro. Furthermore, this catalyst can be used at low loading, even for reactions of sterically hindered substrates. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Peyroux, Eugenie,Berthiol, Florian,Doucet, Henri,Santelli, Maurice
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p. 1075 - 1082
(2007/10/03)
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- Bimolecular formation of radicals by hydrogen transfer, 12: Transfer hydrogenation of p-substituted α-methylstyrenes and of 9-methylenefluorene as a criterion of mechanism
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The uncatalyzed transfer hydrogenation of substituted α-methylstyrenes with 9,10-dihydroanthracene (DHA), xanthene (XAN), or 9,10-dihydroacridine (DHAC) was studied mechanistically. The three hydrogen donors react at very similar rates and with similar activation parameters and with little discrimination between the various substituted styrenes. The kinetic isotope effects are also similar and the solvent effect is small. A hydrogen atom transfer mechanism (retrodisproportionation) is, therefore, preferred to a hydride transfer mechanism. This is supported by the very similar reactivity of the hydrogen transfer reaction of DHA and XAN with 9-methylenefluorene. The product yields in all reactions investigated in this project were >90%. VCH Verlagsgesellschaft mbH, 1997.
- Friebolin, Heike,Roers, Rolf,Ebenhoch, Jochen,Gerst, Matthias,Ruechardt, Christoph
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p. 385 - 389
(2007/10/03)
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- Transfer Hydrogenation of p-Substituted α-Methylstyrenes by 9,10-Dihydroanthracene
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The rate constants k2 of the uncatalyzed transfer hydrogenation of five p-substituted α-methylstyrenes 1a-e vary less then a factor 2 (300 deg C) which supports the proposed radical mechanism (scheme 2) and excludes hydride transfer as an alternative.
- Gerst, Matthias,Ruechardt, Christoph
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p. 7733 - 7736
(2007/10/02)
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