- Di(benzothiazol-2-yl)phosphanide as a janus-head ligand to caesium
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Starting from tris(benzothiazol-2-yl)phosphane (1) an advanced Janus-head ligand, di(benzothiazol-2-yl)phosphane (2), was synthesised and structurally characterised. The heteroaryl substituents of this ligand provide both hard and soft donor sites. Surprisingly, the phosphorus atom in 2 is divalent and the hydrogen atom is directly bonded to one ring nitrogen atom and hydrogen bonded to the second. Compound 2 decomposes in any common solvent other than diethyl ether and a new preparation to improve the yields of 2 is presented. A coordination polymer, [{Cs(bth)2P}8] (3) (bth = benzothiazol-2-yl), was obtained when the sec-phosphane 2 was allowed to react with elemental caesium in a 1:1 ratio in diethyl ether at -78°C. In 3 each anion is coordinated to four caesium cations and vice versa. The central phosphorus atom is coordinated to two metal atoms above and below the mean plane of the anion in positions in which the two lone pairs of a four-electron donor are anticipated. Two additional cations μ-bridge both ring nitrogen atoms. Hence both faces of the Janus-head ligand are coordinated to the same number of metal cations but in a different way.
- Stey, Thomas,Pfeiffer, Matthias,Henn, Julian,Pandey, Sushil K.,Stalke, Dietmar
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- 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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- Transforming LiTMP Lithiation of Challenging Diazines through Gallium Alkyl Trans-Metal-Trapping
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This study establishes a new trans-metal-trapping (TMT) procedure based on a mixture of LiTMP (the base) and tris(trimethylsilylmethyl)gallium [Ga(CH2SiMe3)3, GaR3] (the trap) that, operating in a tandem manner, is effective for the regioselective deprotonation of sensitive diazines in hydrocarbon solution, as illustrated through reactions of pyrazine, pyridazine, and pyrimidine, as well as through the N-S heterocycle benzothiazole. The metallo-activated complexes of all of these compounds were isolated and structurally defined.
- Uzelac, Marina,Kennedy, Alan R.,Hevia, Eva,Mulvey, Robert E.
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p. 13147 - 13150
(2016/10/30)
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- General Reactivity of 2-Lithiobenzothiazole to Various Electrophiles and the Use as a Formyl Anion Equivalent in the Synthesis of α-Hydroxy Carbonyl Compounds
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The reaction of 2-lithiobenzothiazole with a variety of electrophiles such as aldehydes, ketones, carboxylic esters, lactones, nitriles, and amides afforded the expected addition and substitution products.Trimethylsilyl chloride readily reacted with the b
- Chikashita, Hidenori,Ishibaba, Megumi,Ori, Keiji,Itoh, Kazuyoshi
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p. 3637 - 3648
(2007/10/02)
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- Electrophilic Hydroxylation with Bis(trimethylsilyl)peroxide. A Synthon for the Hydroxyl Cation
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The regiospecific introduction of an hydroxy group in aromatic and aliphatic compounds can be performed in good yields by electrophilic hydroxylation of their organometallic derivatives with bis(trimethylsilyl)peroxide.
- Taddei, Maurizio,Ricci, Alfredo
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p. 633 - 635
(2007/10/02)
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- REACTION OF 2-LITHIOBENZOTHIAZOLE WITH ELECTROPHILES AND A SYNTHESIS OF α-HYDROXY ALDEHYDES AND KETONES
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The reaction of 2-lithiobenzothiazole with a variety of electrophiles, exept for alkyl halides and styrene oxide, could be effectively accomplished to give the expected products in high yields.The adducts of lithiobenzothiazole to carbonyl compounds could
- Chikashita, Hidenori,Itoh, Kazuyoshi
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p. 295 - 300
(2007/10/02)
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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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