Asymmetric hydrogenation with water/silane as the hydrogen source.
Asymmetric hydrogenation with water/silane as the hydrogen source.
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DOI：
10.1002/chem.200902790
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发表时间：
2010-01
期刊：
影响因子：
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通讯作者：
Dawei Wang;Duo-Sheng Wang;Qing‐An Chen;Yong‐Gui Zhou
中科院分区：
文献类型：
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作者：
Dawei Wang;Duo-Sheng Wang;Qing‐An Chen;Yong‐Gui Zhou
前手性化合物的催化不对称氢化是制备对映体纯化合物的最有效方法之一。[1]近几十年来，通过使用氢气、[3] iPrOH、[4] HCOOH、[5]和Hantzsch酯[6]作为氢源，在酮、亚胺、烯烃和芳族化合物[2]的不对称氢化中取得了巨大成功，具有优异的对映体选择性[参见Eq.①]。对于不对称氢化，金属氢化物键（MCHH）的形成和反应性是核心主题。通常，活性金属-氢化物键可以通过过渡金属催化剂与上述氢源通过均裂或异裂过程的反应形成。然而，反应性和对映体选择性通常是底物依赖性的。由于没有万能的催化剂对每一个底物，新的策略，在温和的条件下，特别是在无高压釜的条件下形成活性金属氢化物键，是非常可取的。水，在自然界中最丰富的环境友好的来源，已被用于有机合成作为反应试剂和反应介质。[7]尽管在这些领域取得了进展，但在不对称催化中，水作为反应底物的探索要少得多。据我们所知，没有报道以水为氢源发生不对称氢化。通常，由于中心金属的亲氧性，水很难提供氢化物，如[Eq. (2)]因此，通常
Catalytic asymmetric hydrogenation of prochiral compounds is one of most efficient methods to produce enantiopure compounds.[1] In recent decades, great success has been achieved in the asymmetric hydrogenation of ketones, imines, alkenes, and aromatic compounds [2] with excellent enantioselectivity by using hydrogen gas,[3] iPrOH,[4] HCOOH,[5] and Hantzsch esters [6] as the hydrogen source [see Eq.(1)]. For asymmetric hydrogenation, the formation and reactivity of metal–hydride bonds (MÀH) are the core topic. In general, active metal–hydride bonds can be formed by the reaction of transition-metal catalysts and the abovementioned hydrogen sources through homolytic or heterolytic processes. However, reactivities and enantioselectivities are generally substrate dependent. Because there is no omnipotent catalyst for every substrate, new strategies for the formation of active metal–hydride bonds under mild conditions, especially under autoclave-free conditions, are highly desirable.Water, the most abundant environmentally benign source in nature, has been used in organic synthesis as a reaction reagent and a reaction medium.[7] Despite advances in these areas, water is far less explored as a reaction substrate in asymmetric catalysis. To the best of our knowledge, there are no reports of asymmetric hydrogenation occurring with water as the hydrogen source. In general, it is very difficult for water to donate hydride owing to the oxyphilicity of the central metal as shown in [Eq.(2)], and as a result, usually