- Palladium-catalyzed R(sp3)-Zn/R(sp)-SnBu3 oxidative cross-coupling
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A novel bond formation through oxidative cross-coupling with desyl chloride as the oxidant has been investigated. The coupling can be carried out under mild conditions. The Csp3-center carbon was involved even in the presence of a β-H, and up to 90% of the desired cross-coupling product was obtained with the secondary Csp3-center substrate. Georg Thieme Verlag Stuttgart.
- Jin, Liqun,Zhao, Yingsheng,Wang, Haibo,Lei, Aiwen
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p. 649 - 654
(2008/12/21)
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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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- Palladium-catalyzed homocoupling reactions between two Csp3-Csp3 centers
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(Matrix Presented) A novel palladium-catalyzed coupling reaction between two Csp3-Csp3 centers has been investigated. This protocol is initiated by the oxidative addition of an α-halo carbonyl compound to a palladium(0) species, followed by the double transmetalation. The key dialkyl palladium intermediate undergoes reductive elimination to form the desired coupling product.
- Lei, Aiwen,Zhang, Xumu
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p. 2285 - 2288
(2007/10/03)
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- The Surface of Silica as a Medium for the Radical and Ionic Decomposition of Diacyl Peroxides
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The rates of decomposition of β-phenylpropionyl peroxide 1, β-phenylisovaleryl peroxide 2, and β-phenylisovaleryl p-nitrobenzoyl peroxide 3 are much higher on silica surfaces than they are in solution.The products formed on silica surfaces are derived from both radical and ionic precursors except in the case of 3, for which the reaction may be entirely ionic.The relationships between the medium effects on the rates and on the products suggest that the ionic and radical parts of the reaction branch from a common polar intermediate.Both the ionic and radical products differ significantly from those formed in solution.In the neophyl radical, adsorption inhibits the migration of phenyl to form phenyl-tert-butyl radical.In the ionic reaction, there is extensive migration of methyl in competition with phenyl, in contrast to the behavior of neophyl derivatives in solvolysis reaction.Dihydrocoumarin, from 1, and dimethyldihydrocoumarin, from 2 and 3, are not formed at all in solution.Esters, which are often formed via carboxy inversion and related reactions when polar diacyl peroxides decompose in solution, appear to arise from electron transfer in radial-pair precursors.There is no evidence of carboxy inversion compounds or carbonic acid esters in the physically adsorbed products, although some RO-C(=O)+ groups (1-2percent) appear to be trapped by the silica.Rearranged and unrearranged neophyl cations are trapped more extensively as silyl ethers.Other ion-derived products are one of the phenylisobutylenes, several phenylbutenes, and the carboxylic acids.Coadsorbed oxygen or acetonitrile alters the product distribution partly by trapping radicals and partly by site preemption effects.
- Leffler, J.E.,Barbas, J.T.
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p. 7768 - 7773
(2007/10/02)
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