- Small Gold(I) and Gold(I)–Silver(I) Clusters by C?Si Auration
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Auration of o-trimethylsilyl arylphosphines leads to the formation of gold and gold–silver clusters with ortho-metalated phosphines displaying 3c–2e Au?C?M bonds (M=Au/Ag). Hexagold clusters [Au6L4](X)2 are obtained by reaction of (L?TMS)AuCl with AgX, whereas reaction with AgX and Ag2O leads to gold–silver clusters [Au4Ag2L4](X)2. Oxo-trigold(I) species [Au3O]+ were identified as the intermediates in the formation of the silver-doped clusters. Other [Au5], [Au4Ag], and [Au12Ag4] clusters were also obtained. Clusters containing PAu?Au?AuP structural motif display good catalytic activity in the activation of alkynes under homogeneous conditions.
- Pei, Xiao-Li,Pereira, Ana,Smirnova, Ekaterina S.,Echavarren, Antonio M.
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- Copper-Free Double Silylation of 1,2-Dibromobenzenes Using a Mg/LiCl/DMI System
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The reaction of 1,2-dibromobenzenes with chlorotrimethylsilane efficiently proceeded in the presence of Mg and LiCl in DMI under mild conditions, giving 1,2-bis(trimethylsilyl)benzenes in good to high yields. The reaction of 1,2-dibromobenzenes with chlorodimethylsilane under the same conditions afforded the corresponding 1,2-bis(dimethylsilyl)benzenes in high yields. Functional group transformations of 1,2-bis(trimethylsilyl)benzene were conducted to demonstrate the synthetic utility.
- Kitamura, Tsugio,Yamada, Rin,Gondo, Keisuke,Eguchi, Nobuo,Oyamada, Juzo
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p. 2495 - 2500
(2017/05/22)
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- Selective: S -arylation of 2-oxazolidinethiones and selective N -arylation of 2-benzoxazolinones/2-benzimidazolinones
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There exist three possible patterns for the reaction of cyclic 2-oxazolidinethione and 2-benzoxazolidinethione with arynes, namely (a) S-arylation, (b) N-arylation, and (c) aryne insertion into the thiocarbonyl group (CS). Our studies demonstrate that S-arylation wins out affording S-aryl dihydrooxazoles. In contrast, for related reactions of cyclic 2-benzoxazolinone and 2-benzimidazolinone with arynes, it is found that N-arylation outcompetes O-arylation and aryne insertion into the CO group to give N-aryl 2-benzoxazolinones and N-aryl 2-benzimidazolinones.
- Sun, Chu-Han,Lu, Yi,Zhang, Qing,Lu, Rong,Bao, Lin-Qing,Shen, Mei-Hua,Xu, Hua-Dong
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supporting information
p. 4058 - 4063
(2017/07/10)
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- Gold-catalyzed oxidative coupling of arylsilanes and arenes: Origin of selectivity and improved precatalyst
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The mechanism of gold-catalyzed coupling of arenes with aryltrimethylsilanes has been investigated, employing an improved precatalyst (thtAuBr3) to facilitate kinetic analysis. In combination with linear free-energy relationships, kinetic isotope effects, and stoichiometric experiments, the data support a mechanism involving an Au(I)/Au(III) redox cycle in which sequential electrophilic aromatic substitution of the arylsilane and the arene by Au(III) precedes product-forming reductive elimination and subsequent cycle-closing reoxidation of the metal. Despite the fundamental mechanistic similarities between the two auration events, high selectivity is observed for heterocoupling (C-Si then C-H auration) over homocoupling of either the arylsilane or the arene (C-Si then C-Si, or C-H then C-H auration); this chemoselectivity originates from differences in the product-determining elementary steps of each electrophilic substitution. The turnover-limiting step of the reaction involves associative substitution en route to an arene π-complex. The ramifications of this insight for implementation of the methodology are discussed.
- Ball, Liam T.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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supporting information
p. 254 - 264
(2014/01/23)
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- Palladium-catalyzed intermolecular coupling of 2-silylaryl bromides with alkynes: Synthesis of benzosiloles and heteroarene-fused siloles by catalytic cleavage of the C(sp3)-Si bond
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Unusual split: A wide variety of benzosiloles and derivatives are obtained by the Pd-catalyzed intermolecular coupling of 2-silylaryl bromides and alkynes and the accompanying selective cleavage of the C(sp3)-Si bonds as a key step (see scheme). The product spectrum includes benzosiloles, benzothiophene-fused siloles, ladder-type π-conjugated benzosiloles, and thiophene-bridged 2,5-bisbenzosiloles.
- Liang, Yun,Geng, Weizhi,Wei, Junnian,Xi, Zhenfeng
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supporting information; experimental part
p. 1934 - 1937
(2012/03/26)
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- Rhodium-catalyzed coupling of 2-silylphenylboronic acids with alkynes leading to benzosiloles: Catalytic cleavage of the carbon-silicon bond in trialkylsilyl groups
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(Chemical Equation Presented) The reaction of 2-(trimethylsilyl) phenylboronic acid with alkynes in the presence of a rhodium catalyst affords benzosilole derivatives. The arylvinylrhodium intermediate undergoes formal substitution at a silicon center, resulting in the cleavage of a robust silicon-methyl bond in the trimethylsilyl group.
- Tobisu, Mamoru,Onoe, Masahiro,Kita, Yusuke,Chatani, Naoto
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supporting information; experimental part
p. 7506 - 7507
(2009/10/17)
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- Method of producing an o-disubstituted aromatic compound, and method of producing a monosubstituted-monohaloaromatic compound
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A method of producing an o-disubstituted aromatic compound, containing: continuously conducting at least the following steps (a) to (d): (a) a step of mono-lithiating one halogen atom of an o-dihaloaromatic compound, using a first microreactor; (b) a step of making the thus-obtained monolithiated product to react with an electrophilic compound, using a second microreactor, to obtain a monosubstituted-monohaloaromatic compound; (c) a step of lithiating the other halogen atom of the o-dihaloaromatic compound, using a third microreactor; and (d) a step of making the thus-obtained lithiated product successively to react with an electrophilic compound, using a forth microreactor.
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Page/Page column 17
(2008/12/07)
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- Mechanism of Base-Catalyzed Desilylations of Aryl- and Heteroaryltrimethylsilanes
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The influence of different bases on the cleavage of silicium-carbon bonds in aryl- and heteroaryltrimethylsilanes is investigated in the presence of benzaldehyde as electrophilic scavenger for the aryl and heteroaryl anions formed in this process.A reactivity gradation of the various basic catalysts employed is determined from the reactions with 2-(trimethylsilyl)benzothiazole (1).The increase of catalytic activity of the anions parallels that of their ion potential.Attack of the base at the Si atom is postulated as the first step in this reaction sequence, with subsequent dissociation of the pentacoordinated intermediate in the rate-determining step.The carbanion thus liberated rapidly reacts with benzaldehyde.In the differently substituted aryltrimethylsilanes 13, 13', and 13'' the dependency of aryl anion stability in the base-catalyzed carbodesilylation was investigated.The relative rates of reaction correlate with Hammett's ?-constants rather than with the corresponding aryl anion stabilities.
- Effenberger, Franz,Spiegler, Wolfgang
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p. 3872 - 3899
(2007/10/02)
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- THE SYNTHESIS AND REACTIONS OF ortho BROMOPHENYLLITHIUM
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Experimental conditions have now been developed whereby o-bromophenyl-lithium(II) may be prepared in excellent yields and used as an organometallic intermediate for the synthesis of a variety of ortho bromo substituted phenyl compounds (o-BrC6H4X).The thermal stability, decomposition products and reactions of II were studied.Reactions between II and a variety of substrates, e.g., CO2, dimethylformamide, fluorinated esters, hexafluorobenzene, and organosilicon chlorides were examined.
- Chen, Loomis S.,Chen, Grace J.,Tamborski, Christ
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p. 283 - 292
(2007/10/02)
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