Hydrosilation of Carbonyl-Containing Substrates Catalyzed by an Electrophilic η-Silane Iridium(III) Complex.
Hydrosilation of Carbonyl-Containing Substrates Catalyzed by an Electrophilic η-Silane Iridium(III) Complex.
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发表时间：
2010
期刊：
影响因子：
2.8
通讯作者：
Sehoon Park;M. Brookhart
中科院分区：
文献类型：
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作者：
Sehoon Park;M. Brookhart
据报道，使用阳离子铱催化剂 (POCOP)Ir(H)(丙酮)(+), 1, (POCOP = 2,6-双(二叔丁基膦基)苯基)对各种酮和醛进行硅氢化。对于三乙基硅烷，除了特别大的酮之外，所有酮都可以在 25 °C 下使用 0.5 mol% 催化剂在 20-30 分钟内进行定量反应。酯和酰胺的硅氢化分别导致C-O和C-N键的过度还原和断裂。 4-叔丁基环己酮硅氢化的非对映选择性已使用多种硅烷进行了检验，并且高度依赖于温度。使用 EtMe(2)SiH，分析顺式：反式硅氢化产物的比率随温度的变化，得出 ΔΔH(‡) (ΔH(‡) (反式) - ΔH(‡) (顺式)) 和 ΔΔS(‡) (ΔS(‡) (反式) - ΔS(‡)(顺式)) 的值为 -2.5 kcal/mol 和 -6.9 e.u.， 分别。机理研究表明，酮络合物 (POCOP)Ir(H)(酮)(+) 处于催化剂静止状态，并与低浓度的硅烷络合物 (POCOP)Ir(H)(HSiR(3))(+) 保持平衡。硅烷络合物将 R(3)Si(+) 转移至酮，形成氧碳鎓离子 R(3)SiOCR'(2) (+)，该离子被生成的中性二氢化物 3 (POCOP)Ir(H)(2) 还原，生成产物 R(3)SiOCHR'(2) 和 (POCOP)IrH(+)，从而结束催化循环。
Hydrosilation of a variety of ketones and aldehydes using the cationic iridium catalyst, (POCOP)Ir(H)(acetone)(+), 1, (POCOP = 2,6-bis(di-tert-butyl phosphinito)phenyl) is reported. With triethyl silane, all but exceptionally bulky ketones undergo quantitative reactions employing 0.5 mol% catalyst in 20-30 min at 25 °C. Hydrosilation of esters and amides results in over-reduction and cleavage of C-O and C-N bonds, respectively. The diastereoselectivity of hydrosilation of 4-tert-butyl cyclohexanone has been examined using numerous silanes and is highly temperature dependent. Using EtMe(2)SiH, analysis of the ratio of cis:trans hydrosilation products as a function of temperature yields values for ΔΔH(‡) (ΔH(‡) (trans) - ΔH(‡) (cis)) and ΔΔS(‡) (ΔS(‡) (trans) - ΔS(‡)(cis)) of -2.5 kcal/mol and -6.9 e.u., respectively. Mechanistic studies show that the ketone complex, (POCOP)Ir(H)(ketone)(+), is the catalyst resting state and is in equilibrium with low concentration of the silane complex, (POCOP)Ir(H)(HSiR(3))(+). The silane complex transfers R(3)Si(+) to ketone forming the oxocarbenium ion, R(3)SiOCR'(2) (+), which is reduced by the resulting neutral dihydride 3, (POCOP)Ir(H)(2), to yield product R(3)SiOCHR'(2) and (POCOP)IrH(+) which closes the catalytic cycle.