- Synthesis and reactivity of a zwitterionic palladium allyl complex supported by a perchlorinated carboranyl phosphine
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A zwitterionic palladium complex of a phosphine bearing a perchlorinated carba-closo-dodecaborate anion as a ligand substituent is reported. A single-crystal X-ray diffraction study reveals that, in the solid state, one of the chlorides of the carborane cage occupies a coordination site of the square-planar complex. However, in solution, the P-carborane bond of the ligand is rapidly rotating at temperatures as low as -90 °C, which demonstrates the carborane substituent's weak coordinative ability even though this anion is covalently linked to the phosphine ligand. The complex is thermally stable and catalyzes the vinyl addition polymerization of norbornene.
- Estrada, Jess,Woen, David H.,Tham, Fook S.,Miyake, Garret M.,Lavallo, Vincent
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Read Online
- Electrochemical-induced radical allylation via the fragmentation of alkyl 1,4-dihydropyridines
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Aldehydes are abundant chemical motifs presented in natural products and pharmaceuticals. As a radical precursor, its application is limited. Dihydropyridines (DHPs) can act as masked aldehydes, providing alkyl radicals under the activation of Lewis acid, heat, SET oxidant and light irradiation. Herein, we report the direct activation of 4-alkyl DHPs via single electron transfer at the anode. C–C bond homolysis at the C4-position of DHP generated the corresponding alkyl radical, which was captured subsequently by 2-phenyl and 2-ethoxy carbonyl allyl bromide. The following intramolecular elimination reaction afforded 20 different radical allylation products bearing various alkyl substituents with yields up to 92%.
- Chen, Xiaoping,Luo, Xiaosheng,Wang, Ping
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- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
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Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
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p. 6684 - 6690
(2021/05/31)
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- Intermolecular [4 + 2] process of N-acyliminium ions with simple olefins for construction of functional substituted-1,3-oxazinan-2-ones
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An efficient approach to functionalized 4,6-disubstituted-and 4,6,6-trisubstituted-1,3-oxazinan-2-ones skeleton has been developed through the reaction of semicyclic N,O-acetals 4a and 4b with 1,1-disubstituted ethylenes 5 or 8. As a result of such a [4 +
- Han, Xiaoli,Nie, Xiaodi,Feng, Yiman,Wei, Bangguo,Si, Changmei,Lin, Guoqiang
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supporting information
p. 3526 - 3530
(2021/06/12)
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- Iron-Catalyzed Highly Enantioselective Hydrogenation of Alkenes
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Here, we reported for the first time an iron-catalyzed highly enantioselective hydrogenation of minimally functionalized 1,1-disubstituted alkenes to access chiral alkanes with full conversion and excellent ee. A novel chiral 8-oxazoline iminoquinoline ligand and its iron complex have been designed and synthesized. This protocol is operationally simple by using 1 atm of hydrogen gas and shows good functional group tolerance. A primary mechanism has been proposed by the deuterium-labeling experiments.
- Lu, Dongpo,Lu, Peng,Lu, Zhan,Ren, Xiang,Sun, Yufeng,Xu, Haofeng
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supporting information
p. 12433 - 12438
(2021/08/23)
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- Cobalt(II)-Catalyzed Stereoselective Olefin Isomerization: Facile Access to Acyclic Trisubstituted Alkenes
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Stereoselective synthesis of trisubstituted alkenes is a long-standing challenge in organic chemistry, due to the small energy differences between E and Z isomers of trisubstituted alkenes (compared with 1,2-disubstituted alkenes). Transition metal-catalyzed isomerization of 1,1-disubstituted alkenes can serve as an alternative approach to trisubstituted alkenes, but it remains underdeveloped owing to issues relating to reaction efficiency and stereoselectivity. Here we show that a novel cobalt catalyst can overcome these challenges to provide an efficient and stereoselective access to a broad range of trisubstituted alkenes. This protocol is compatible with both mono- and dienes and exhibits a good functional group tolerance and scalability. Moreover, it has proven to be a useful tool to construct organic luminophores and a deuterated trisubstituted alkene. A preliminary study of the mechanism suggests that a cobalt-hydride pathway is involved in the reaction. The high stereoselectivity of the reaction is attributed to both a π-πstacking effect and the steric hindrance between substrate and catalyst.
- Zhang, Sheng,Bedi, Deepika,Cheng, Lu,Unruh, Daniel K.,Li, Guigen,Findlater, Michael
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supporting information
p. 8910 - 8917
(2020/12/23)
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- Nickel-Catalyzed Benzylation of Aryl Alkenes with Benzylamines via C-N Bond Activation
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We have developed the first example of nickel-catalyzed Heck-type benzylation of aryl olefins with various benzylamines as benzyl electrophiles, and the benzylic C-N bond cleavage was efficiently promoted by the amine-I2 charge transfer complex (CT complex). The combination of low-cost NiCl2 and I2 has been found to facilitate Heck reaction of tertiary benzylamines and alkenes into various benzyl-substituted alkenes in good to excellent yields. This unconventional Heck reaction is proposed to go through initially the formation of a benzylic radical via oxidative addition of the C-N bond with Ni(0), then capturing by aryl alkene via radical addition, followed by single-electron transfer redox and proton abstraction without oxidant and external base.
- Yu, Hui,Hu, Bin,Huang, Hanmin
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p. 13922 - 13929
(2018/11/23)
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- Nickel-Catalyzed Direct Synthesis of Aryl Olefins from Ketones and Organoboron Reagents under Neutral Conditions
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Nickel-catalyzed addition of arylboron reagents to ketones results in aryl olefins directly. The neutral condition allows acidic protons of alcohols, phenols, and malonates to be present, and fragile structures are also tolerated.
- Lei, Chuanhu,Yip, Yong Jie,Zhou, Jianrong Steve
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supporting information
p. 6086 - 6089
(2017/05/08)
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- Effect of Lewis acids and low temperature initiators on the allyl transfer reaction involving phthalimido-N-oxyl radical
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Previously, we reported allyl transfer reactions of allyl bromide and allyl phthalimido-N-oxyl substrates with hydrocarbons that result in CC bond formation. In both cases, efficient chain transfer processes along with high reaction yields were observed. Since PINO chemistry leads to an environmentally friendly method of hydrocarbon functionalization, additional studies were performed in order to improve the process. To expand the utility of this reaction, we carried out experiments to optimize reaction conditions and tested the effect of Lewis acids and low temperature initiators. Although allyl-PINO substrates reacted slightly slower than the bromides, the reactions were cleaner with little or no side products. The chain lengths for these reactions were compromised at lower temperatures, attributable to the high activation energy required for the hydrogen atom abstraction by PINO. The addition of a Lewis acid catalyst (AlCl3) improves the product yield and reaction rate, possibly due to the formation of a PINO/AlCl3 complex which lowers the activation energy for hydrogen abstraction step.
- Patil, Shradha,Chen, Liang,Tanko, James M.
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supporting information
p. 7029 - 7033
(2015/01/09)
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- C-H Bond Functionalization with the Formation of a C-C Bond: A Free Radical Condensation Reaction Based on the Phthalimido-N-oxyl Radical
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The development of a new chemical process that effects the conversion RH + C=C-C-X → R-C-C=C + HX, in which X is the phthalimido-N-oxyl radical (PINO·), is reported. The reaction yields are high, mass balances are excellent, and C-H bond functionalization and C-C bond formation are achieved in a single transformation. The byproduct of the reaction, N-hydroxyphthalimide, precipitates from solution and can be easily removed by simple filtration (and recycled). The kinetic chain lengths are shorter and the reaction times are longer (relative to those of the analogous reactions of allyl bromides), most likely because PINO· is a less-reactive hydrogen-atom abstractor. There appears to be no significant difference in efficiency in the addition-elimination steps. Competition experiments reveal that Br· and PINO· are comparable in leaving group ability.
- Patil, Shradha,Chen, Liang,Tanko, James M.
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p. 502 - 505
(2015/10/05)
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- Scope and mechanism of homogeneous tantalum/iridium tandem catalytic alkane/alkene upgrading using sacrificial hydrogen acceptors
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An in-depth investigation of a dual homogeneous catalyst system for the coupling of alkanes and alkenes based on an early-/late-transition-metal pairing is reported. The system is composed of Cp*TaCl2(alkene) for alkene dimerization and pincer-iridium hydrides for alkane/alkene transfer hydrogenation. Because there is no kinetically relevant interaction between the two catalysts, the tandem mechanism can be entirely described using the two independent catalytic cycles. The alkene dimerization mechanism is characterized by an entropically disfavored pre-equilibrium between Cp*TaCl 2(1-hexene) + 1-hexene and Cp*TaCl 2(metallacyclopentane) (ΔH° = -22(2) kcal/mol; ΔS° = -16(2) eu); thus, the overall rate of alkene dimerization is positive order in 1-hexene (exhibiting saturation kinetics), and increases only modestly with temperature. In contrast, the rate of 1-hexene/n-heptane transfer hydrogenation catalyzed by t-Bu[PCP]IrH4 is inverse order in 1-hexene and increases substantially with temperature. Styrene has been investigated as an alternate sacrificial hydrogen acceptor. Styrene dimerization catalyzed by Cp*TaCl2(alkene) is considerably slower than 1-hexene dimerization. The conversion of styrene/heptane mixtures by the Ta/Ir tandem system leads to three product types: styrene dimers, coupling of styrene and heptane, and heptene dimers (from heptane). Through careful control of reaction conditions, the production of heptene dimers can be favored, with up to 58% overall yield of heptane-derived products and cooperative TONs of up to 12 and 10 for Ta and Ir catalysts, respectively. There is only slight inhibition of Ir-catalyzed styrene/n-heptane transfer hydrogenation under the tandem catalysis conditions.
- Leitch, David C.,Labinger, Jay A.,Bercaw, John E.
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supporting information
p. 3353 - 3365
(2014/08/05)
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- TANDEM TRANSFER HYDROGENATION AND OLIGOMERIZATION FOR HYDROCARBON PRODUCTION
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The disclosure provides for hydrocarbon production by hydrogenation and oligomerizaton and, more particularly, to catalysis of alkanes and alkenes by a tandem transfer hydrogenation and oligomerization.
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Paragraph 0125
(2014/07/23)
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- C-H bond functionalization with the formation of a C-C bond: A free radical condensation reaction based on the phthalimido-N-oxyl radical
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The development of a new chemical process that effects the conversion RH + C=C-C-X → R-C-C=C + HX, in which X is the phthalimido-N-oxyl radical (PINO·), is reported. The reaction yields are high, mass balances are excellent, and C-H bond functionalization and C-C bond formation are achieved in a single transformation. The byproduct of the reaction, N-hydroxyphthalimide, precipitates from solution and can be easily removed by simple filtration (and recycled). The kinetic chain lengths are shorter and the reaction times are longer (relative to those of the analogous reactions of allyl bromides), most likely because PINO· is a less-reactive hydrogen-atom abstractor. There appears to be no significant difference in efficiency in the addition-elimination steps. Competition experiments reveal that Br· and PINO· are comparable in leaving group ability. The introduction of a new chain carrier, the phthalimido-N-oxyl radical (PINO·), leads to an improved chain reaction. This chain reaction is successful and high reaction yields are reported for the functionalization of hydrocarbons. Kinetic studies reveal that this reaction is an efficient chain process, and the leaving group ability of PINO · is comparable to that of Br·. Copyright
- Patil, Shradha,Chen, Liang,Tanko, James M.
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p. 502 - 505
(2014/02/14)
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- Copper-catalyzed oxidative heck reactions between alkyltrifluoroborates and vinyl arenes
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We report herein that potassium alkyltrifluoroborates can be utilized in oxidative Heck-type reactions with vinyl arenes. The reaction is catalyzed by a Cu(OTf)2/1,10-phenanthroline with MnO2 as the stoichiometric oxidant. In addition to the alkyl Heck, amination, esterification, and dimerization reactions of alkyltrifluoroborates are demonstrated under analogous reaction conditions. Evidence for an alkyl radical intermediate is presented.
- Liwosz, Timothy W.,Chemler, Sherry R.
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supporting information
p. 3034 - 3037
(2013/07/26)
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- Reactions of a cationic geminal Zr+/P pair with small molecules
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The metallocene cation complex [Cp*2ZrCH3] +[B(C6F5)4]- inserts the phosphino-substituted alkyne Ph-Ci - 1/4C-PPh2 into the [Zr]-CH3 bond to form the internally phosphane-stabilized cation [Cp*2Zr-C(=CMePh)PPh2]+ (10). Complex 10 adds alkyl isocyanides as well as pivalonitrile at a lateral site at the bent metallocene wedge with retention of the Zr-P bond. Complex 10 acts as a reactive frustrated Lewis pair toward heterocumulenes, undergoing Zr+/P addition reactions to the carbonyl groups of an alkyl isocyanate and of carbon dioxide to form the respective five-membered metallaheterocyclic adducts 13 and 14. With mesityl azide complex 10 undergoes a Zr+/P FLP N,N-addition reaction at the terminal azide nitrogen atom to form the four-membered FLP cycloadduct 15. The Zr+/P FLP is a reactive hydrogen activator. In a stoichiometric reaction it generates a hydridozirconocene cation that subsequently serves as a hydrogenation catalyst for various olefinic or acetylenic substrates. The Zr+/P pair 10 undergoes selective 1,4-addition reactions to conjugated enones and to a conjugated ynone to give the corresponding seven-membered metallacyclic Zr+/P FLP addition products. Many compounds of this study were characterized by X-ray diffraction.
- Xu, Xin,Kehr, Gerald,Daniliuc, Constantin G.,Erker, Gerhard
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supporting information
p. 6465 - 6476
(2013/06/26)
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- Selective dimerization of aryl-substituted terminal alkynes on bis(indenyl)zirconocene derivatives
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Dimerization of aryl-substituted terminal alkynes on indenyl zirconium complexes occurred in a selective way. 1,4-Aryl-1,3-diene derivatives were formed exclusively after hydrolysis. It is in sharp contrast to the reaction on [Cp2Zr] complexes.
- Ren, Shenyong,Seki, Takashi,Necas, David,Shimizu, Hiroyuki,Nakajima, Kiyohiko,Kanno, Ken-Ichiro,Song, Zhiying,Takahashi, Tamotsu
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supporting information
p. 1443 - 1444
(2013/05/21)
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- Catalytic asymmetric dihydroxylation of enamides and application to the total synthesis of (+)-tanikolide
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Asymmetric dihydroxylation of β,β- disubstituted enamides afforded chiral tertiary-alcohol-containing α-hydroxyaldehydes and 1,2-diols with high enantioselectivity (see scheme). This method was applied to the total synthesis of the antifungal natural prod
- Gourdet, Benoit,Lam, Hon Wai
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supporting information; experimental part
p. 8733 - 8737
(2011/01/07)
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- Radical additions to allyl bromides. A synthetically useful, 'Tin-Free' method for carbon-carbon bond formation
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The scope and limitations of a novel free radical chain process involving the addition of benzyl radicals to substituted allyl bromides were examined and extended to explore the effect of α-substitution on the allyl bromide (R′), and the use of pyrrolidine amides and oxazolidinone as activating substituents (Z) as the first steps toward the development of a stereoselective, radical-based C-C bond-forming reaction which is environmentally benign.
- Struss, John A.,Sadeghipour, Mitra,Tanko, James M.
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supporting information; scheme or table
p. 2119 - 2120
(2009/07/19)
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- Efficient metal-catalyzed hydroarylation of styrenes
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A highly efficient metal-catalyzed hydroarylation of various styrenes has been developed. This new bismuth-catalyzed C-H functionalization provides straightforward access to a series of valuable 1,1-diarylalkane products.
- Rueping, Magnus,Nachtsheim, Boris J.,Scheidt, Thomas
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p. 3717 - 3719
(2007/10/03)
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- Isolation and characterisation of aromatic substituted olefinic compounds from the starfish Pteraster militaris
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Two series of the polyaromatic coumpound (1-6 and 7-14) have been isolated from the starfish Pteraster militaris after column chromatography over Amberlite XAD-2 resin.Their structures have been established by spectroscopic means and confirmed as 2,4-diph
- Yayli, Nurettin
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p. 556 - 561
(2007/10/03)
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