A complex situation: Asymmetricepoxidation of conjugatedolefins was achieved at room temperature using ruthenium complex 1 as the catalyst and air as the oxidant to give epoxides in up to 95 % ee (see scheme). When the product was acid sensitive, the reaction was carried out at 0 °C under oxygen.
Designing New Chiral Ketone Catalysts. Asymmetric Epoxidation of <i>cis</i>-Olefins and Terminal Olefins
作者:Hongqi Tian、Xuegong She、Hongwu Yu、Lianhe Shu、Yian Shi
DOI:10.1021/jo010838k
日期:2002.4.1
class of chiral oxazolidinone ketone catalyst for asymmetric epoxidation. High ee values have been obtained for a number of cyclic and acyclic cis-olefins. The epoxidation was stereospecific with no isomerization observed in the epoxidation of acyclic systems. Encouragingly high ee values have also been obtained for a number of terminalolefins. Mechanistic studies show that electronic interactions play
clarified, some experimental results support the notion that an aqua ligand coordinated with the ruthenium ion serves as a protontransfer agent for the oxygen activation process, and it is recycled and used as the protontransfermediator during the process. Thus, we have achieved catalytic asymmetric oxygen atom transfer reaction using molecular oxygen that can be carried out under ambient conditions.
Biocatalytic Cascade Conversion of Racemic Epoxides to (
<i>S</i>
)‐2‐Arylpropionic Acids, (
<i>R</i>
)‐ and (
<i>S</i>
)‐2‐Arylpropyl Amines
作者:Willy W. L. See、Xirui Li、Zhi Li
DOI:10.1002/adsc.202201061
日期:2023.1.10
New types of one-pot multi-step enzymatic cascade transformation involving dynamic kinetic resolution to convert racemic substrates to chiral products in high ee and yield were developed. Unique cascade reactions of easily accessible racemic trans-β-methyl or α-methyl epoxides to produce (S)-2-arylpropionic acids, (R)- and (S)-2-arylpropyl amines were demonstrated via styrene oxide isomerase (SOI)-catalyzed
开发了新型一锅多步酶促级联转化,涉及动态动力学拆分,以将外消旋底物转化为高ee和收率的手性产物。通过氧化苯乙烯异构酶 (SOI) 证明了容易获得的外消旋反式-β-甲基或 α-甲基环氧化物产生 ( S )-2-芳基丙酸、( R )- 和 ( S )-2-芳基丙基胺的独特级联反应-催化 Meinwald 环氧化物重排原位生成 2-芳基丙醛,随后自发消旋化,以及乙醇脱氢酶 (ADH)-催化的 ( S )-对映选择性氧化或转氨酶 (TA)-催化的 ( R )- 或 (S)-对映选择性胺化,分别。用分离的酶或全细胞生物催化剂进行的级联反应产生具有高对映选择性和产量的药学相关 ( S )-2-芳基丙酸、( R )- 和 ( S )-2-芳基丙基胺。从环氧化物原位生成醛开始的级联有效地减少了与醛不稳定性相关的副反应,并显示出广泛的底物范围。