共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Karin Weidner Zhongdong Sun Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》2015,54(21):6236-6240
A direct aldol reaction of an α‐azido 7‐azaindolinylamide, promoted by a Cu‐based cooperative catalyst, is documented. Aromatic aldehydes bearing an ortho substituent exhibited diastereodivergency depending on the nature of the chiral ligands used. Smooth reactions with ynals highlighted the broad substrate scope. A vicinal azido alcohol unit in the product allowed direct access to the corresponding aziridine and facile hydrolysis of the 7‐azaindolinylamide moiety furnished enantioenriched β‐hydroxy‐α‐azido carboxylic acid derivatives. 相似文献
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Direct Asymmetric Michael Reaction of α,β‐Unsaturated Aldehydes and Ketones Catalyzed by Two Secondary Amine Catalysts 下载免费PDF全文
Prof. Dr. Yujiro Hayashi Nariyoshi Umekubo 《Angewandte Chemie (International ed. in English)》2018,57(7):1958-1962
A direct asymmetric Michael reaction of α,β‐unsaturated aldehydes and ketones proceeded in the presence of two pyrrolidine‐type catalysts, a diphenylprolinol silyl ether and hydroxyproline, to afford synthetically useful δ‐keto aldehydes with excellent diastereo‐ and enantioselectivity. Although there are several iminium ions and enamines in the reaction mixture, the iminium ion generated by the former catalyst reacts preferentially with the enamine generated by the latter catalyst. 相似文献
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Antonia Mielgo Dr. Irene Velilla Claudio Palomo Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(25):7496-7502
In the presence of p‐nitrobenzoic acid, the O‐nitroso aldol reaction of nitrosobenzene with enolisable aldehydes may be promoted by commercially available α,α‐diphenylprolinol trimethylsilyl ether. The reaction proceeds with good yields and essentially complete enantioselectivity, with catalyst loadings in the 5–10 mol % range. The resulting α‐oxyaldehyde adducts may be transformed in situ into α‐oxyimines, which provide 1,2‐amino alcohols upon treatment with Grignard reagents, in good overall yield (45–59 %) and with typical diastereomeric ratios ≥95:5. 相似文献
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Taichi Kano Dr. Yukako Yamaguchi Keiji Maruoka Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(27):6678-6687
Amino sulfonamide catalyst : A distal proton of the axially chiral amino sulfonamide (S)‐ 1 realized the opposite diastereoselectivity in Mannich and cross‐aldol reactions compared with that observed in proline‐catalyzed reactions. The reactions catalyzed by (S)‐ 1 proceeded smoothly to give the anti‐Mannich and syn‐aldol adducts in excellent enantioselectivity (see scheme).
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Haizea Echave Dr. Rosa López Prof. Dr. Claudio Palomo 《Angewandte Chemie (International ed. in English)》2016,55(10):3364-3368
The first enantioselective direct cross‐aldol reaction of α‐keto amides with aldehydes, mediated by a bifunctional ureidopeptide‐based Brønsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydrogen‐bond donor groups in the catalyst structure promoted the exclusive generation of the α‐keto amide enolate which reacted with either non‐enolizable or enolizable aldehydes to produce highly enantioenriched polyoxygenated aldol adducts without side‐products resulting from dehydration, α‐keto amide self‐condensation, aldehyde enolization, and isotetronic acid formation. 相似文献
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Xin Feng Hai‐Lei Cui Shi Xu Li Wu Prof. Dr. Ying‐Chun Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10309-10312
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On the Mechanism of the Organocatalytic Asymmetric Epoxidation of α,β‐Unsaturated Aldehydes 下载免费PDF全文
Dr. Rebecca L. Davis Dr. Kim L. Jensen Dr. Björn Gschwend Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):64-67
Mechanistic studies on the organocatalytic epoxidation of α,β‐unsaturated aldehydes explore the autoinductive behavior of the reaction and establish that the hydrate/peroxyhydrate of the product is acting as a phase‐transfer catalyst. Based on these studies, an improved methodology that provides high selectivities and decreased catalyst loading, through the addition of chloral hydrate, is developed. 相似文献
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Xin Feng Hai‐Lei Cui Shi Xu Li Wu Prof. Dr. Ying‐Chun Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(44):12227-12227
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The 4,5‐methano‐L‐proline was used as chiral organocatalysts in direct asymmetric aldol reactions. Under the optimal conditions, excellent enantioselectivities (up to 99% ee) were obtained with high chemical yields (up to 95%) for a series of aldehydes using only 5 mol% catalyst loading. To show the practicality of the method, the reaction was tested at a large scale. The reaction was complete in 16 h, and the aldol product was obtained in 86% yield and 93% ee. 相似文献
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Diphenylprolinol Silyl Ether Catalyzed Asymmetric Michael Reaction of Nitroalkanes and β,β‐Disubstituted α,β‐Unsaturated Aldehydes for the Construction of All‐Carbon Quaternary Stereogenic Centers 下载免费PDF全文
Prof. Dr. Yujiro Hayashi Yuya Kawamoto Masaki Honda Daichi Okamura Shigenobu Umemiya Yuka Noguchi Takasuke Mukaiyama Prof. Dr. Itaru Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12072-12082
The asymmetric Michael reaction of nitroalkanes and β,β‐disubstituted α,β‐unsaturated aldehydes was catalyzed by diphenylprolinol silyl ether to afford 1,4‐addition products with an all‐carbon quaternary stereogenic center with excellent enantioselectivity. The reaction is general for β‐substituents such as β‐aryl and β‐alkyl groups, and both nitromethane and nitroethane can be employed. The addition of nitroethane is considered a synthetic equivalent of the asymmetric Michael reaction of ethyl and acetyl substituents by means of radical denitration and Nef reaction, respectively. The short asymmetric synthesis of (S)‐ethosuximide with a quaternary carbon center was accomplished by using the present asymmetric Michael reaction as the key step. The reaction mechanism that involves the E/Z isomerization of α,β‐unsaturated aldehydes, the retro‐Michael reaction, and the different reactivity between nitromethane and nitroethane is discussed. 相似文献
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Qiying Zhang Prof. Dr. Xiuling Cui Dr. Long Zhang Prof. Dr. Sanzhong Luo Hui Wang Prof. Dr. Yangjie Wu 《Angewandte Chemie (International ed. in English)》2015,54(17):5210-5213
Presented herein is a redox tuning strategy for asymmetric aminocatalysis with a designed chiral ferrocenophane. Under redox control, the ferrocenophane catalyst efficiently catalyzes the asymmetric aldol reaction at room temperature with excellent yield and good stereoselectivity. Moreover, the redox‐active ferrocene moiety also served as phase‐tag to facilitate catalyst recovery and reuse. The catalyst can be reused for five cycles without much loss of activity. Ferrocenium of the oxidized ferrocenophane was proposed to serve as Lewis acidic site, thus accounting for the stereo control. 相似文献
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Jie Liu Jin Zhu Dr. Hualiang Jiang Prof. Dr. Wei Wang Prof. Dr. Jian Li Prof. Dr. 《化学:亚洲杂志》2009,4(11):1712-1716
An o‐anisidine‐Pd(OAc)2 catalytic system for the direct co‐catalytic Saegusa oxidation of β‐aryl substituted aldehydes to α,β‐unsaturated aldehydes has been developed. The use of o‐anisidine in place of (S)‐diphenylprolinol made the process more simply and cost‐effective. The process not only features the use of unmodified aldehydes rather than enol silyl ethers, but also gives moderate to good yields (44–72 %). 相似文献
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Xiaohong Chen Yin Zhu Zhen Qiao Mingsheng Xie Lili Lin Dr. Xiaohua Liu Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10124-10129
An easily available and efficient chiral N,N′‐dioxide–nickel(II) complex catalyst has been developed for the direct catalytic asymmetric aldol reaction of α‐isothiocyanato imide with aldehydes which produces the products in morderate to high yields (up to 98 %) with excellent diastereo‐ (up to >99:1 d.r.) and enantioselectivities (up to >99 % ee). A variety of aromatic, heteroaromatic, α,β‐unsaturated, and aliphatic aldehydes were found to be suitable substrates in the presence of 2.5 mol % L ‐proline‐derived N,N′‐dioxide L5 –nickel(II) complex. This process was air‐tolerant and easily manipulated with available reagents. Based on experimental investigations, a possible transition state has been proposed to explain the origin of reactivity and asymmetric inductivity. 相似文献
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Direct Catalytic Asymmetric Doubly Vinylogous Michael Addition of α,β‐Unsaturated γ‐Butyrolactams to Dienones 下载免费PDF全文
Xiaodong Gu Tingting Guo Yuanyuan Dai Allegra Franchino Jie Fei Chuncheng Zou Prof. Dr. Darren J. Dixon Prof. Dr. Jinxing Ye 《Angewandte Chemie (International ed. in English)》2015,54(35):10249-10253
An asymmetric doubly vinylogous Michael addition (DVMA) of α,β‐unsaturated γ‐butyrolactams to sterically congested β‐substituted cyclic dienones with high site‐, diastereo‐, and enantioselectivity has been achieved. An unprecedented DVMA/vinylogous Michael addition/isomerization cascade reaction affords chiral fused tricyclic γ‐lactams with four newly formed stereocenters. 相似文献