- Construction of Axial Chirality and Silicon-Stereogenic Center via Rh-Catalyzed Asymmetric Ring-Opening of Silafluorenes
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A rhodium-catalyzed enantioselective ring-opening/acylation of silafluorenes is reported. The newly developed bulky phosphoramidite ligand, in combination with methanol as the additive, enabled the reaction to create one axial chirality and one silicon-stereogenic center in a highly selective manner by only cleavage of one Si-C bond.
- Bi, Xiufen,Feng, Jia,Xue, Xiaoping,Gu, Zhenhua
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- Thermal hydrosilylation of olefin with hydrosilane. Preparative and mechanistic aspects
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The reaction of trichlorosilane (1a) at 250 °C with cycloalkenes, such as cyclopentene (2a), cyclohexene (2b), cycloheptene (2c), and cyclooctene (2d), gave cycloalkyltrichlorosilanes [CnH2n-1SiCl3: n = 5 (3a), 6 (3b), 7 (3c), 8 (3d)] within 6 h in excellent yields (97-98%), but the similar reactions using methyldichlorosilane (1b) instead of 1a required a longer reaction time of 40 h and afforded cycloalkyl(methyl)dichlorosilanes [CnH2n-1SiMeCl2: n = 5 (3e), 6 (3f), 7 (3g), 8 (3h)] in 88-92% yields with 4-8% recovery of reactant 2. In large (2, 0.29 mol)-scale preparations, the reactions of 2a and 2b with 1a (0.58 mol) under the same condition gave 3a and 3b in 95% and 94% isolated yields, respectively. The relative reactivity of four hydrosilanes [HSiCl3-mMem: m = 0-3] in the reaction with 2a indicates that as the number of chlorine-substituent(s) on the silicon increases the rate of the reaction decreases in the following order: n = 3 > 2 > 1 ? 0. In the reaction with 1a, the relative reactivity of four cycloalkenes (ring size = 5-8) decreases in the following order: 2d > 2a > 2c > 2b. Meanwhile linear alkenes like 1-hexene undergo two reactions of self-isomerization and hydrosilylation with hydrosilane to give a mixture of the three isomers (1-, 2-, and 3-silylated hexanes). In this reaction, the reactivity of the terminal 1-hexene is higher than the internal 2- and 3-hexene. The redistribution of hydrosilane 1 and the polymerization of olefin 2 occurred rarely under the thermal reaction condition.
- Jung, Dong Euy,Han, Joon Soo,Yoo, Bok Ryul
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experimental part
p. 3687 - 3692
(2011/11/29)
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- Organosilicon derivatives of cyclopentane
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Addition of HMe3-nSiCln (n = 1-3) to cyclopentene yields the corresponding cyclopentylchloro-silanes. Their ethynyl derivatives were prepared by the reaction with ethynylmagnesium bromide. The reaction of cyclopentyldimethyl(bromomagnesioethynyl)silane with acetaldehyde gives 1-(cyclopentyldimethylsilyl)-1-butyn-3-ol. When treated with EtMgBr and Me3SiCl, cyclopentyltriethynylsilane gives cyclopentyldiethynyl-(trimethylsilylethynyl)silane. The reaction between cyclopentyltrichlorosilane and methanol produces cyclopentyltrimethoxysilane, and the reaction of the latter with triethanolamine gives cyclopentylsilatrane.
- Yarosh,Mirskov,Yarosh,Albanov,Voronkov
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p. 242 - 244
(2007/10/03)
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