Direct synthesis of aryl halosilanes through iridium(I)-catalyzed aromatic C-H silylation by disilanes
Direct synthesis of aryl halosilanes through iridium(I)-catalyzed aromatic C-H silylation by disilanes
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DOI：
10.1002/anie.200352399
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发表时间：
2003-01-01
影响因子：
16.6
通讯作者：
Miyaura, N
中科院分区：
文献类型：
--
作者：
Ishiyama, T;Sato, K;Miyaura, N
芳基卤代硅烷及其超价衍生物是现代有机合成中碳-碳 [1-2] 和碳-杂原子 [3] 键形成的通用试剂。尽管它们是通过卤代硅烷与芳基镁或芳基锂试剂的芳基化制备的，[4]以及通过钯催化的卤代乙硅烷与芳基亲电试剂的交叉偶联[5]，从经济、效率和环境友好的角度来看，通过C-H键活化直接对芳烃进行甲硅烷基化将提供更具吸引力的路线。事实上，几个研究小组已经开发了由过渡金属络合物催化的乙硅烷 [6] 或氢硅烷 [6a, 7] 进行的芳香族 CÀH 甲硅烷基化。然而，该方案的应用仅限于芳基三有机硅烷的合成。另一方面，我们最近发现由1/2 [{IrCl (cod)} 2](cod= 1, 5-cyclooctadiene)或1/2 [{Ir (OMe)(cod)} 2]和2, 2'-联吡啶(bpy)或4, 4'-二叔丁基-2, 2'-联吡啶(dtbpy)生成IrI配合物是优良的芳香族催化剂 双 (pinacolato) 二硼的 CÀH 硼化。[8]这些结果促使我们将该方法扩展到芳烃 (2) 在 1/2 [{Ir (OMe)(cod)} 2]-dtbpy 催化剂存在下通过 1, 2-二叔丁基-1, 1, 2, 2-四氟二硅烷 (tBuF2Si) 2 (1) 进行芳族 CÀH 硅烷化反应。该过程首次能够通过芳香族 CÀH 键活化直接合成芳基卤代硅烷 (3)（方案 1）。我们最初的研究重点是乙硅烷上的取代基对反应的影响。使用乙硅烷(1.0mmol)、苯(60mmol)、[{Ir(OMe)-(cod)}2](0.015mmol)和dtbpy(0.03mmol)在可重新密封的Schlenk管中在808℃下进行反应16小时。在所检查的乙硅烷中，1表现出最高的反应性，以28%的产率和28%的1转化率产生相应的苯基硅烷。四氟乙硅烷的使用至关重要，因为(Me2FSi) 2以9%的产率产生相应的芳基硅烷，而(tBuCl2Si) 2或(Me3Si) 2没有反应。烷基取代基的结构对甲硅烷基化也有显着影响。例如，(sBuF2Si) 2 和(nBuF2Si) 2 不形成甲硅烷基化产物。
Aryl halosilanes and their hypervalent derivatives are versatile reagents for carbon–carbon [1–2] and carbon–heteroatom [3] bond formation in modern organic synthesis. Although they have been prepared by arylation of halosilanes with aryl magnesium or aryl lithium reagents,[4] and by Pd-catalyzed cross-coupling of halogenated disilanes with aryl electrophiles,[5] direct silylation of arenes through CÀH bond activation would provide a more attractive route from the viewpoints of economy, efficiency, and environmental benignity. Indeed, aromatic CÀH silylation by disilanes [6] or hydrosilanes [6a, 7] catalyzed by a transition-metal complex has been developed by several research groups. However, the application of this protocol has been limited to the synthesis of aryl triorganosilanes. On the other hand, we recently found that IrI complexes generated from 1/2 [{IrCl (cod)} 2](cod= 1, 5-cyclooctadiene) or 1/2 [{Ir (OMe)(cod)} 2] and 2, 2’-bipyridine (bpy) or 4, 4’-di-tert-butyl-2, 2’-bipyridine (dtbpy) are excellent catalysts for aromatic CÀH borylation by bis (pinacolato) diboron.[8] These results prompted us to extend the methodology to the aromatic CÀH silylation of arenes (2) by 1, 2-ditert-butyl-1, 1, 2, 2-tetrafluorodisilane (tBuF2Si) 2 (1) in the presence of a 1/2 [{Ir (OMe)(cod)} 2]-dtbpy catalyst. This process enables, for the first time, the direct synthesis of aryl halosilanes (3) through aromatic CÀH bond activation (Scheme 1).Our initial investigation focused on the effects of substituents on the disilanes on the reaction. The reactions were carried out at 808C for 16 h in a resealable Schlenk tube by using disilanes (1.0 mmol), benzene (60 mmol),[{Ir (OMe)-(cod)} 2](0.015 mmol), and dtbpy (0.03 mmol). Among the disilanes examined, 1 exhibited the highest reactivity to produce the corresponding phenylsilane in 28% yield with 28% conversion of 1. The use of tetrafluorodisilanes is critical as (Me2FSi) 2 gave the corresponding arylsilane in 9% yield, and (tBuCl2Si) 2 or (Me3Si) 2 led to no reaction. The structures of alkyl substituents also had significant effects on silylation. For example,(sBuF2Si) 2 and (nBuF2Si) 2 formed no silylated product.