1829-43-2Relevant articles and documents
Metal-free hydrogen evolution cross-coupling enabled by synergistic photoredox and polarity reversal catalysis
Cao, Jilei,Lu, Kanghui,Ma, Lishuang,Yang, Xiaona,Zhou, Rong
supporting information, p. 8988 - 8994 (2021/11/23)
A synergistic combination of photoredox and polarity reversal catalysis enabled a hydrogen evolution cross-coupling of silanes with H2O, alcohols, phenols, and silanols, which afforded the corresponding silanols, monosilyl ethers, and disilyl ethers, respectively, in moderate to excellent yields. The dehydrogenative cross-coupling of Si-H and O-H proceeded smoothly with broad substrate scope and good functional group compatibility in the presence of only an organophotocatalyst 4-CzIPN and a thiol HAT catalyst, without the requirement of any metals, external oxidants and proton reductants, which is distinct from the previously reported photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cationviavisible-light photoredox catalysis.
Heavier Alkaline-Earth Catalyzed Dehydrocoupling of Silanes and Alcohols for the Synthesis of Metallo-Polysilylethers
Hill, Michael S.,Mahon, Mary F.,Manners, Ian,Morris, Louis J.,S. McMenamy, Fred,Whittell, George R.
supporting information, p. 2954 - 2966 (2020/03/04)
The dehydrocoupling of silanes and alcohols mediated by heavier alkaline-earth catalysts, [Ae{N(SiMe3)2}2?(THF)2] (I–III) and [Ae{CH(SiMe3)2}2?(THF)2], (IV–VI) (Ae=Ca, Sr, Ba) is described. Primary, secondary, and tertiary alcohols were coupled to phenylsilane or diphenylsilane, whereas tertiary silanes are less tolerant towards bulky substrates. Some control over reaction selectivity towards mono-, di-, or tri-substituted silylether products was achieved through alteration of reaction stoichiometry, conditions, and catalyst. The ferrocenyl silylether, FeCp(C5H4SiPh(OBn)2) (2), was prepared and fully characterized from the ferrocenylsilane, FeCp(C5H4SiPhH2) (1), and benzyl alcohol using barium catalysis. Stoichiometric experiments suggested a reaction manifold involving the formation of Ae–alkoxide and hydride species, and a series of dimeric Ae–alkoxides [(Ph3CO)Ae(μ2-OCPh3)Ae(THF)] (3 a–c, Ae=Ca, Sr, Ba) were isolated and fully characterized. Mechanistic experiments suggested a complex reaction mechanism involving dimeric or polynuclear active species, whose kinetics are highly dependent on variables such as the identity and concentration of the precatalyst, silane, and alcohol. Turnover frequencies increase on descending Group 2 of the periodic table, with the barium precatalyst III displaying an apparent first-order dependence in both silane and alcohol, and an optimum catalyst loading of 3 mol % Ba, above which activity decreases. With precatalyst III in THF, ferrocene-containing poly- and oligosilylethers with ferrocene pendent to- (P1–P4) or as a constituent (P5, P6) of the main polymer chain were prepared from 1 or Fe(C5H4SiPhH2)2 (4) with diols 1,4-(HOCH2)2-(C6H4) and 1,4-(CH(CH3)OH)2-(C6H4), respectively. The resultant materials were characterized by NMR spectroscopy, gel permeation chromatography (GPC) and DOSY NMR spectroscopy, with estimated molecular weights in excess of 20,000 Da for P1 and P4. The iron centers display reversible redox behavior and thermal analysis showed P1 and P5 to be promising precursors to magnetic ceramic materials.
Metal-Free Ammonium Iodide Catalyzed Oxidative Dehydrocoupling of Silanes with Alcohols
Yuan, Yan-Qin,Kumar, Pailla Santhosh,Guo, Sheng-Rong
supporting information, p. 1620 - 1623 (2017/08/11)
An ammonium iodide catalyzed direct oxidative coupling of silanes with alcohols to give various alkoxysilane derivatives was discovered. tert -Butyl hydroperoxide proved to be an efficient oxidant for this transformation. Attractive features of this protocol include its transition-metal-free nature and the mild reaction conditions.
