Selective Asymmetric Transfer Hydrogenation of α‐Substituted Acetophenones with Bifunctional Oxo‐Tethered Ruthenium(II) Catalysts,Advanced Synthesis & Catalysis

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Selective Asymmetric Transfer Hydrogenation of α‐Substituted Acetophenones with Bifunctional Oxo‐Tethered Ruthenium(II) Catalysts
Advanced Synthesis & Catalysis ( IF 4.4 ) Pub Date : 2017-12-04 , DOI: 10.1002/adsc.201701227
Yamato Yuki ₁ , Taichiro Touge ₁ , Hideki Nara ₁ , Kazuhiko Matsumura ₁ , Mitsuhiko Fujiwhara ₁ , Yoshihito Kayaki ₂ , Takao Ikariya ₂

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A practical method for the asymmetric transfer hydrogenation of α‐substituted ketones was developed utilizing oxo‐tethered N‐sulfonyldiamine‐ruthenium complexes. Reduction by HCO₂H and HCO₂K in a mixed solvent of EtOAc/H₂O allowed for the selective synthesis of halohydrins from 2‐bromoacetophenone (98%) and 2‐chloroacetophenone (>99%), leading to suppressed undesired side reactions stemming from formylation under the typical reaction conditions using an azeotropic 5:2 mixture of HCO₂H and Et₃N. A range of functional groups, such as halogens, methoxy, nitro, dimethylamino, and ester groups, were well tolerated, highlighting the potential of this method. Nearly complete selectivity with a preferable ee was maintained even with a substrate/catalyst (S/C) ratio of 5000. This catalyst system was also effective for the asymmetric reduction of α‐sulfonated ketones without eroding the leaving group.

中文翻译：

双功能氧栓合钌（II）催化剂对α取代的苯乙酮的选择性不对称转移加氢

利用氧连接的N-磺酰基二胺-钌络合物开发了一种实用的方法，用于α-取代酮的不对称转移加氢。在EtOAc / H ₂ O混合溶剂中通过HCO ₂ H和HCO ₂ K还原，可以从2-溴苯乙酮（98％）和2-氯苯乙酮（> 99％）选择性合成卤代醇，从而抑制了不良的副反应在典型的反应条件下，使用HCO ₂ H和Et _3的5：2共沸混合物，从甲酰化反应中提取N.一系列功能基团（如卤素，甲氧基，硝基，二甲基氨基和酯基）的耐受性良好，凸显了该方法的潜力。即使底物/催化剂（S / C）为5000，也能保持接近完全的选择性和较好的ee。这种催化剂体系对于不对称地还原α-磺化酮也有效，而不会侵蚀离去基团。

更新日期：2017-12-04

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