- Cycloneophylpalladium(IV) Complexes: Formation by Oxidative Addition and Selectivity of Their Reductive Elimination Reactions
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The cycloneophylpalladium(II) complexes [Pd(CH2CMe2C6H4)(κ2-N,N′-L)] (L = RO(CH2)3N(CH2-2-C5H4N)2, R = H, Me) undergo oxidation to Pd(IV) with bromine or iodine to give [PdX(CH2CMe2C6H4)(κ3-N,N′,N″-L)]X (X = Br, I) or with methyl iodide to give the transient complexes [PdMe(CH2CMe2C6H4)(κ3-N,N′,N″-L)]I. The products of Br2 and I2 oxidation, [PdX(CH2CMe2C6H4)(κ3-N,N′,N″-L)]X (X = Br, I), are sufficiently stable to be isolated, but they decompose slowly in solution by reductive elimination to give the palladium(II) products [PdX(κ3-N,N′,N″-L)]X (X = Br, I). The organic products are formed via either CH2-Ar or CH2-X bond formation. In the latter case, neophyl rearrangement and protonolysis steps follow reductive elimination to give a mixture of organic products. The methylpalladium(IV) complexes [PdMe(CH2CMe2C6H4)(κ3-N,N′,N″-L)]I decompose at 0 °C by selective reductive elimination with Me-Ar bond coupling to give the alkylpalladium(II) complex [Pd(CH2CMe2-2-C6H4Me)(κ3-N,N′,N″-L)]I. The mechanisms of the reactions have been explored by kinetic studies.
- Behnia, Ava,Blacquiere, Johanna M.,Fard, Mahmood A.,Puddephatt, Richard J.
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p. 4037 - 4050
(2020/12/01)
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- Oxidative cross-coupling through double transmetallation: Surprisingly high selectivity for palladium-catalyzed cross-coupling of alkylzinc and alkynylstannanes
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Two different organometallic reagents now can cross-couple together with the oxidative cross-coupling strategy. Palladium catalyzed oxidative cross-couplings of alkylzinc and alkynylstannane reagents using desyl chloride as the oxidant have been explored, which produce the desired Csp-Csp3 cross-coupling product in surprisingly high selectivity and yields. The current catalytic system tolerates the presence of β-H, and the reactions using long chain alkyl zinc reagents gave the cross-coupling product in excellent yields and selectivities. Copyright
- Zhao, Yingsheng,Wang, Haibo,Hou, Xiaohui,Hu, Yanhe,Lei, Aiwen,Zhang, Heng,Zhu, Lizheng
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p. 15048 - 15049
(2007/10/03)
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- Determination of the rate constants of the addition of primary alkyl radicals to allylstannanes
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The rate constants and the activation parameters of the addition of primary alkyl radicals to allyldibutyl-4,7,10-trioxaundecylstannane 1 and (2-ethoxycarbonylprop-2-enyl)dibutyl-4,7,10-trioxaundecylstannane 2 were determined by studying their respective free radical reactions with (2-bromo-1,1-dimethylethyl)benzene and 6-bromohex-1-ene at different temperatures.
- Ferkous, Fouad,Degueil-Castaing, Marie,Deleuze, Herve,Maillard, Bernard
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p. 247 - 250
(2007/10/03)
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- Catalytic activity of K10-montmorillonite in reaction of arenes with some mono- and di-functional alkylating agents, mostly derived from isobutane and isobutene
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K10-montmorillonite has been tested as Friedel-Crafts catalyst in the alkylation of benzene, toluene and anisole with one or more of the alkylating agents 1-10. The reaction products consisted essentially of 1,1- and 1,2-diaryl-2-methylpropane derivatives (e.g. 11 and 12 respectively) together with side products resulting from transalkylation, monoalkylation, hvdride transfer and elimination. K 10-montmorillonite has also been used to catalyse the alkylation of naphthalene with benzyl alcohol whereby a mixture of α-and β-benzylnaphthalene is obtained. The results, explained in terms of carbocation transformations, show K 10-montmorillonite to be a mild catalyst with no subsequent side-chain isomerising ability just like FeCl3, AlCl3-CH3NO2, TiCl4 and ZrCl4.
- Albar,Basaif,Khalaf, Ali A.
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p. 161 - 166
(2007/10/03)
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- REACTIONS OF BrCl WITH ALKYL RADICALS.
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It is demonstrated that photohalogenation of low reactivity substrates with BrCl occurs mainly with Cl. selectivity.With tertiary or benzylic hydrogens in the substrate, mainly Br. selectivity is observed.These observations are rationalized, taking into account the relative concentrations of halogen atoms and their respective rates of hydrogen abstractions.The resultant radicals react with BrCl to make (RBr/RCl) in ratios between 1 and 15.
- Skell, P. S.,Baxter, H. N.,Tanko, J. M.
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p. 5181 - 5184
(2007/10/02)
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- Organofluorosilicates in Organic Synthesis. XVI. Synthesis of Organopentafluorosilicates via the Diels-Alder, Ene, and Friedel-Crafts Reaction. Their Transformations to Organic Halides and Alcohols
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Described herein are several representative examples of cleavage reactions of otherwise hardly accessible organopentafluorosilicates which are obtainable via the Diels-Alder reaction, ene reaction, and the Friedel-Crafts reaction of vinyl-, ethynyl-, or allyl-trichlorosilanes.The Diels-Alder reaction between vinyltrichlorosilane and o-xylylene generated in situ by debromination of α,α'-dibromo-o-xylene afforded (1,2,3,4-tetrahydro-2-naphthyl)-trichlorosilane which was converted to the corresponding silicate.The silicate reacted with NBS and MCPBA to give the respective bromide and alcohol.The Diels-Alder reaction between ethynyltrichlorosilane and methyl coumalate gave a mixture of meta and para isomers of methyl (trichlorosilyl)benzoate in the ratio of 55/45, the silicate of which reacted with NBS to give two positional isomers of methyl bromobenzoate.The electronic effect of the methoxycarbonyl group on the Si-C bond cleavage was small.The silicate derived from 4-octenyltrichlorosilane which was obtained by the ene reaction between vinyltrichlorosilane and 1-hexene afforded, upon treatment with NBS, 4-octenyl bromide in the ratio of E/Z=83/17.The sterically crowded neophylsilicate obtainable via the Friedel-Crafts reaction of 2-methyl-1-propenyltrichlorosilane with benzene underwent the cleavage reaction with NBS in methanol.Neophyl bromide was formed with CuBr2 in a low yield, no product being formed arising from rearrangement of the neophyl radical.
- Tamao, Kohei,Yoshida, Jun-ichi,Akita, Munetaka,Sugihara, Yoshihiro,Iwahara, Takahisa,Kumada, Makoto
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p. 255 - 260
(2007/10/02)
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