Thiaminediphosphatedependentenzymes are well known for catalyzing the asymmetricsynthesis of chiral α‐hydroxy ketones from simple prochiral substrates. The steric and chemical properties of the enzyme active site define the product spectrum. Enzymes catalyzing the carboligation of aromatic aldehydes to (S)‐benzoins have not so far been identified. We were able to close this gap by constructing
N′-dioxide complex as catalyst. This strategy provided an array of optically active 2-acyl-2-hydroxy cyclohexanones in moderate to good yields with high enantioselectivities. The asymmetric isomerizations of acyclic α-hydroxy aldehydes and α-iminols were achieved as well under modified conditions, affording the corresponding chiral α-hydroxy ketones and α-amino ketones in moderate results. Moreover, further
Benzaldehyde Lyase-Catalyzed Direct Amidation of Aldehydes with Nitroso Compounds
作者:Peruze Ayhan、Ayhan S. Demir
DOI:10.1002/adsc.201000735
日期:2011.3.7
furnishes N‐arylhydroxamic acids in high yields. Aromatic aldehydes and benzoins are converted into enamine‐carbanion‐like intermediates prior to their reaction with nitroso compounds. The kinetic resolution of rac‐2‐hydroxy‐1,2‐diphenylethanones furnished (S)‐benzoins and arylhydroxamic acids with high enantioselectivities and conversions.
Chiral Benzoins via Asymmetric Transfer Hemihydrogenation of Benzils: The Detail that Matters
作者:Lorena De Luca、Antonio Mezzetti
DOI:10.1021/acs.joc.9b03408
日期:2020.5.1
The synthesis of enantiomericallypure benzoins by hydrogenation of readily available benzils has been long thwarted by their base-sensitivity. We show here that an iron(II) hydride complex catalyzes the asymmetrictransferhydrogenation of benzils from 2-propanol. When strictly base-free conditions are granted, excellent enantioselectivity is achieved even with o-substituted substrates, which are
通过容易获得的苯偶酰氢化合成对映体纯的苯偶姻一直受到其碱敏感性的阻碍。我们在这里展示了一种铁 (II) 氢化物配合物催化 2-丙醇中苯偶酰的不对称转移氢化。当获得严格的无碱条件时,即使使用邻位取代的底物也能实现出色的对映选择性,这对于用其他方法制备特别具有挑战性。因此,在优化的反应条件下,在较短的反应时间(30-75 分钟)内以良好的收率(高达 83%)和优异的对映选择性(高达 98% ee)制备了手性安息香。此外,这项工作证实,当使用金属催化剂时,苯偶姻产物的两种对映异构体都可以得到,这明显优于酶法。