Asymmetric hydrogenation of aromatic, aliphatic, and α,β-unsaturated acyl silanes catalyzed by tol-binap/pica ruthenium(II) complexes:: Practical synthesis of optically active α-hydroxysilanes
Asymmetric hydrogenation of aromatic, aliphatic, and α,β-unsaturated acyl silanes catalyzed by tol-binap/pica ruthenium(II) complexes:: Practical synthesis of optically active α-hydroxysilanes
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DOI：
10.1002/anie.200704696
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Ohkuma, Takeshi
中科院分区：
文献类型：
--
作者：
Arai, Noriyoshi;Suzuki, Ken;Ohkuma, Takeshi
光学活性的α-羟基硅烷是一类带有功能基团的手性有机金属化合物。这些分子及其衍生物被用于立体控制的C13 C键的形成和重排，从而产生了各种手性有机化合物。[1-5]酰基硅烷的不对称还原是制备手性仲α-羟基硅烷的一种简单方法。硼氢化与B-氯二异松甲基硼烷（Ipc 2BCl）是最广泛使用的方法，这一重要的转变。[1，3a，4d-h，5-7]手性恶唑硼烷试剂对于炔属酰基硅烷的反应是有效的。[4i手性氨基锂以优异的对映选择性还原α，β-不饱和酰基硅烷。[8]近年来，以异丙醇为还原剂，芳烃/N-（对甲苯磺酰基）-1，2-二苯基乙二胺（Ts-dpen）Ru Ⅱ配合物为催化剂，对芳香族酰基硅烷进行了转移氢化反应。[3c]虽然这是该反应的唯一催化化学方法，但33-200的底物与催化剂摩尔比（S/C）对于实际应用是不令人满意的。据报道，不对称微生物还原仅对特定酰基硅烷底物表现出高立体选择性。[3b因此，非常需要开发用于酰基硅烷的催化不对称还原的有效方法。从原子经济性和实用性的观点来看，加氢还原法具有许多其他还原方法所不能比拟的优点。[10]在此，我们首次公开了由Tolbinap/Pica RuII络合物催化的酰基硅烷的高度对映选择性氢化。[11反应在10 atm H2下以高达10 000的S/C值进行。得到一系列苄基、脂肪族和烯丙基α-羟基硅烷，ee值高达99%。
Optically active α-hydroxysilanes are regarded as a kind of chiral organometallic compound with a functional group. These molecules and their derivatives have been utilized for stereocontrolled CÀC bond formation and rearrangement, which resulted in a variety of chiral organic compounds.[1–5] Asymmetric reduction of acyl silanes is a straightforward method to produce the chiral secondary α-hydroxysilanes. Hydroboration with B-chlorodiisopinocampheylborane (Ipc2BCl) is the most widely used method for this important transformation.[1, 3a, 4d–h, 5–7] The chiral oxazaborolidine reagent is effective for the reaction of acetylenic acyl silanes.[4i, j, 5] A chiral lithium amide reduces α, β-unsaturated acyl silanes with excellent enantioselectivity.[8] However, these procedures require more than one equivalent of the chiral reagent to the substrate.A recently reported transfer hydrogenation catalyzed by an arene/N-(p-toluenesulfonyl)-1, 2-diphenylethylenediamine (Ts-dpen) RuII complex using 2-propanol as a reducing agent is effective for aromatic acyl silanes.[3c] Although this is the only catalytic chemical process for this reaction, the substrateto-catalyst molar ratio (S/C) of 33–200 is not satisfactory for practical use. Asymmetric microbial reductions are reported to exhibit high stereoselectivity merely for specific acyl silane substrates.[3b, 9] Thus, the development of an efficient procedure for the catalytic asymmetric reduction of acyl silanes is highly desirable. Hydrogenation possesses advantages over many other reduction methods from the atom-economical and practical points of view.[10] Herein, we disclose for the first time the highly enantioselective hydrogenation of acyl silanes catalyzed by Tolbinap/pica RuII complexes.[11, 12] The reaction is conducted with a S/C value as high as 10 000 under 10 atm of H2. A series of benzylic, aliphatic, and allylic α-hydroxysilanes is obtained in up to 99% ee.