Enantioselective Epoxidation of Electron-Deficient Alkenes Catalyzed by Manganese Complexes with Chiral N<sub>4</sub>
Ligands Derived from Rigid Chiral Diamines
作者:Xiangning Chen、Bao Gao、Yijin Su、Hanmin Huang
DOI:10.1002/adsc.201700541
日期:2017.8.7
series of tetradentate sp2N/sp3N hybrid chiral N4 ligands derived from rigid chiral diamines were synthesized, which enabled the first manganese-catalyzed enantioselective epoxidation of electron-deficientalkenes with hydrogenperoxide (H2O2) as an oxidant. The reaction furnishes enantiomerically pure epoxy amides, epoxy ketones as well as epoxy esters in good yields and excellent enantioselectivities
合成了一系列衍生自刚性手性二胺的四齿sp 2 N / sp 3 N杂合手性N 4配体,这使锰能够以过氧化氢(H 2 O 2)为氧化剂,首次对缺电子烯烃进行对映选择性环氧化。。该反应以较低的催化剂负载量提供了对映体纯的环氧酰胺,环氧酮以及环氧酯,具有良好的收率和优异的对映选择性(最高99.9%ee)。对结构-活性关系的初步研究表明,保持sp 3的相对较低的供电子能力N和N 2配体的sp 2 N的相对较高的供电子能力有利于获得更高的活性和选择性,从而为我们理解H 2 O 2的环氧化提供了新的视角。
Catalytic asymmetric epoxidation of α,β-unsaturated carboxylic acid imidazolides and amides by lanthanide–BINOL complexes
Highly enantioselective catalytic asymmetric epoxidation of α,β-unsaturatedcarboxylic acid imidazolides and simple amides was developed. In the presence of 5–10 mol% of lanthanide–BINOL complexes, the reaction proceeded smoothly with high substrate generality. In particular, in the cases of α,β-unsaturated amides, there was nearly perfect enantioselectivity (>99% ee). The corresponding epoxides were
Catalytic Asymmetric Epoxidation of α,β-Unsaturated Amides: Efficient Synthesis of β-Aryl α-Hydroxy Amides Using a One-Pot Tandem Catalytic Asymmetric Epoxidation−Pd-Catalyzed Epoxide Opening Process
catalytic asymmetric epoxidation of alpha,beta-unsaturated amides using Sm-BINOL-Ph3As=O complex was succeeded. Using 5-10 mol % of the asymmetric catalyst, a variety of amides were epoxidized efficiently, yielding the corresponding alpha,beta-epoxy amides in up to 99% yield and in more than 99% ee. Moreover, the novel one-pot tandem process, one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide
Dynamic Ligand Exchange of the Lanthanide Complex Leading to Structural and Functional Transformation: One-Pot Sequential Catalytic Asymmetric Epoxidation-Regioselective Epoxide-Opening Process
The characteristic property of the lanthanide complex, which easily undergoes a dynamic ligand exchange and alters its structure and function in situ, is described. After the completion of the catalytic asymmetric epoxidation of various a,beta-unsaturated amides 2 in the presence of the Sm-(S)-BINOL-Ph3As=O (1:1:1) complex 1 (2-10 mol %), the addition of Me3SiN3 directly to the reaction mixture led to smooth epoxide-opening at room temperature, affording the corresponding anti-beta-azido-alpha-hydroxyamide 4 in excellent overall yield (up to 99%) with complete regioselectivity and excellent enantiomeric excess (up to >99%). The key to the success of the sequential process was the in situ generation of the highly reactive samarium azide complex through dynamic ligand exchange. In situ IR spectroscopy and other experiments provided strong evidence that the samariurn azide complex was generated. In addition, the relatively high Lewis basicity of the amide moiety had a key role in the high reactivity of both the epoxidation and the epoxide-opening reactions. Examinations of other nucleophiles such as sulfur or carbon nucleophiles as well as transformations of epoxide-opened products are also described.
Efficient Synthesis of Chiralα- andβ-Hydroxy Amides: Application to the Synthesis of (R)-Fluoxetine