- Nickel-Catalyzed C-H Silylation of Arenes with Vinylsilanes: Rapid and Reversible β-Si Elimination
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The reaction of C6F5H and H2C=CHSiMe3 with catalytic [iPr2Im]Ni(2-H2C=CHSiMe3)2 (1b) exclusively forms the C-H silylation product C6F5SiMe3 with ethylene as a byproduct ([iPr2Im] = 1,3-di(isopropyl)imidazole-2-ylidene). Catalytic C-H bond silylation is facile with partially fluorinated aromatic substrates containing two ortho fluorine substituents adjacent to the C-H bond and 1,2,3,4-tetrafluorobenzene. Less fluorinated substrates react slower. Under the same reaction conditions, catalytic [IPr]Ni(η2-H2C=CHSiMe3)2 (1a) ([IPr] = 1,3-bis[2,6-diisopropylphenyl]-1,3-dihydro-2H-imidazol-2-ylidene) provided only the alkene hydroarylation product C6F5CH2CH2SiMe3. Mechanistic studies reveal that the C-H activation and β-Si elimination steps are reversible under catalytic conditions with both catalysts 1a and 1b. With catalytic 1a, reversible ethylene loss after β-Si elimination was also observed despite its inability to catalyze C-H silylation; the reductive elimination step to form the silylation product is much slower than reductive elimination to form the alkene hydroarylation product. Reversible ethylene loss was not observed with 1b, which suggests that the rate-limiting step in the reaction is neither C-H activation nor β-Si elimination but either ethylene loss or reductive elimination of cis-disposed aryl and SiMe3 moieties.
- Elsby, Matthew R.,Johnson, Samuel A.
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supporting information
p. 9401 - 9407
(2017/07/22)
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- REACTIONS OF POLYFLUORO AROMATIC COMPOUNDS WITH ELECTROPHILIC AGENTS IN THE PRESENCE OF TRIS(DIALKYLAMINO)PHOSPHINES. I. SYNTHESIS OF TRIALKYLSILYL(GERMYL, STANNYL, OR PLUMBYL)POLYFLUOROBENZENES
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Polyfluorophenyl bromides and iodides react with alkylhalo derivatives of silicon, germanium, tin, or lead in the presence of equimolar amounts of a tris(dialkylamino)phosphine to give polyfluorophenyl(alkyl) derivatives of the above-mentioned elements and phosphonium salts.Electron-donor substituents in position 4 of the polyfluorophenyl bromide slow down the reaction, while electron-acceptor substituents accelerate it.
- Bardin, V. V.,Pressman, L. S.,Rogoza, L. N.,Furin, G. G.
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p. 1931 - 1937
(2007/10/02)
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- REACTIONS OF POLYFLUOROARYL BROMIDES AND IODIDES WITH C-, Si-, Ge-, Sn- AND Pb-ELECTROPHILES AND TRIS(DIALKYLAMINO)PHOSPHINES
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The reactions of polyfluoroaryl bromides ArFBr or iodides ArFI with P(NR'2)3 and R3MX (R = alkyl; M = Si, Ge, Sn and Pb; X = Cl, Br) led to the formation of ArFMR3.The reactions of C6F5Br with P(NEt2)3 and C-electrophiles (CH3I, C6F5CF3 and (CF3)2C=CFC2F5) gave the products of pentafluorophenylation of these substrates.
- Bardin, V. V.,Pressman, L. S.,Rogoza, L. N.,Furin, G. G.
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p. 213 - 231
(2007/10/02)
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