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1.
Asymmetric Construction of Pyrrolidines Bearing a Trifluoromethylated Quaternary Stereogenic Center via CuI‐Catalyzed 1,3‐Dipolar Cycloaddition of Azomethine Ylides with β‐CF3‐β,β‐Disubstituted Nitroalkenes 下载免费PDF全文
Dr. Li‐Wei Tang Bao‐Jing Zhao Li Dai Man Zhang Prof. Dr. Zhi‐Ming Zhou 《化学:亚洲杂志》2016,11(17):2470-2477
A direct and convenient method has been developed for the synthesis of optically active pyrrolidines bearing a quaternary stereogenic center containing a CF3 group at the C‐3 position of the pyrrolidine ring. The synthesis system, CuI/Si‐FOXAP‐catalyzed exo‐selective 1,3‐dipolar cycloaddition of azomethine ylides with β‐CF3‐β,β‐disubstituted nitroalkenes, provides pyrrolidines with high diastereoselectivities (up to >98:2 d.r.) and excellent enantioselectivities (up to >99.9 ee) and performs well for a broad scope of substrates under mild conditions. 相似文献
2.
A Cinchona Alkaloid‐Functionalized Mesostructured Silica for Construction of Enriched Chiral β‐Trifluoromethyl‐β‐Hydroxy Ketones over An Epoxidation‐Relay Reduction Process 下载免费PDF全文
Cuibao Li Xiaomin Shu Liang Li Genwei Zhang Ronghua Jin Tanyu Cheng Prof. Guohua Liu 《化学:亚洲杂志》2016,11(14):2072-2077
A cinchona alkaloid‐functionalized heterogeneous catalyst is prepared through a thiol‐ene click reaction of chiral N‐(3,5‐ditrifluoromethylbenzyl)quininium bromide and a mesostructured silica, which is obtained by co‐condensation of 1,2‐bis(triethoxysilyl)ethane and 3‐(triethoxysilyl)propane‐1‐thiol. Structural analyses and characterizations disclose its well‐defined chiral single‐site active center, and electron microscopy images reveal its monodisperse property. As a heterogenous catalyst, it enables an efficient asymmetric epoxidation of achiral β‐trifluoromethyl‐β,β‐disubstituted enones, the obtained chiral products can then be converted easily into enriched chiral β‐trifluoromethyl‐β‐hydroxy ketones through a sequential epoxidation‐relay reduction process. Furthermore, such a heterogeneous catalyst can be recovered conveniently and reused in asymmetric epoxidation of 4,4,4‐trifluoro‐1,3‐diphenylbut‐2‐enone, showing an attractive feature in a practical construction of enriched chiral β‐CF3‐substituted molecules. 相似文献
3.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(1):63-71
New asymmetric conjugate reduction of β,β‐disubstituted α,β‐unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6‐bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)‐4‐Phenyl‐3‐penten‐2‐one and (E)‐4‐phenyl‐4‐isopropyl‐3‐penten‐2‐one were readily reduced at 60 °C in 95 % ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO)2MeSiH proved to be the best hydrogen donor of choice. tert‐Butyl (E)‐β‐methylcinnamate and β‐isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98 % ee. 相似文献
4.
Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source 下载免费PDF全文
A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX3 (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition. 相似文献
5.
AgF‐Mediated Fluorinative Cross‐Coupling of Two Olefins: Facile Access to α‐CF3 Alkenes and β‐CF3 Ketones 下载免费PDF全文
Dr. Bing Gao Dr. Yanchuan Zhao Prof. Dr. Jinbo Hu 《Angewandte Chemie (International ed. in English)》2015,54(2):638-642
A AgF‐mediated fluorination with a concomitant cross‐coupling between a gem‐difluoroolefin and a non‐fluorinated olefin is reported. This highly efficient method provides facile access to both α‐CF3 alkenes and β‐CF3 ketones, which otherwise remain challenging to be directly prepared. The application of this method is further demonstrated by the synthesis of bioactive isoxazoline derivatives. This approach represents a conceptually novel route to trifluoromethylated compounds that combines the in situ generation of the CF3 moiety and a C? H functionalization in a single reaction system. 相似文献
6.
Gonzalo Blay Dr. Isabel Fernández Dr. M. Carmen Muñoz Prof. Dr. José R. Pedro Prof. Dr. Carlos Vila 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9117-9122
Chiral complexes of BINOL‐based ligands with zirconium tert‐butoxide catalyze the Friedel–Crafts alkylation reaction of indoles with β‐trifluoromethyl‐α,β‐unsaturated ketones to give functionalized indoles with an asymmetric tertiary carbon center attached to a trifluoromethyl group. The reaction can be applied to a large number of substituted α‐trifluoromethyl enones and substituted indoles. The expected products were obtained with good yields and ees of up to 99 %. 相似文献
7.
Zhonglin Liu Haiwen Xiao Benxiang Zhang Haigen Shen Lin Zhu Chaozhong Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2532-2535
Reported herein is an unprecedented protocol for trifluoromethylation of unactivated aliphatic C(sp3)?H bonds. With Cu(OTf)2 as the catalyst, the reaction of N‐fluoro‐substituted carboxamides (or sulfonamides) with Zn(CF3)2 complexes provides the corresponding δ‐trifluoromethylated carboxamides (or sulfonamides) in satisfactory yields under mild reaction conditions. A radical mechanism involving 1,5‐hydrogen atom transfer of N‐radicals followed by CF3‐transfer from CuII?CF3 complexes to the thus formed alkyl radicals is proposed. 相似文献
8.
Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
9.
NH2SO3H–SiO2/water as a novel catalytic system was used for the synthesis of (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT‐IR, X‐ray diffraction and scanning electron microscopic–energy dispersion analytical X‐ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis. 相似文献
11.
Synthesis of β‐Substituted γ‐Aminobutyric Acid Derivatives through Enantioselective Photoredox Catalysis 下载免费PDF全文
Jiajia Ma Jiahui Lin Lifang Zhao Dr. Klaus Harms Michael Marsch Dr. Xiulan Xie Prof. Dr. Eric Meggers 《Angewandte Chemie (International ed. in English)》2018,57(35):11193-11197
β‐Substituted chiral γ‐aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β‐substituted γ‐aminobutyric acid derivatives through visible‐light‐induced photocatalyst‐free asymmetric radical conjugate additions is reported. Various β‐substituted γ‐aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42–89 %) and with excellent enantioselectivity (90–97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)‐pregabalin, (R)‐baclofen, (R)‐rolipram, and (S)‐nebracetam. 相似文献
12.
Visible‐Light‐Promoted Dearomative Fluoroalkylation of β‐Naphthols through Intermolecular Charge Transfer 下载免费PDF全文
Quanping Guo Mengran Wang Hong Liu Prof. Dr. Rui Wang Prof. Dr. Zhaoqing Xu 《Angewandte Chemie (International ed. in English)》2018,57(17):4747-4751
The first visible‐light‐promoted dearomative fluoroalkylation of β‐naphthols was realized without the assistance of any transition‐metal catalysts or external photosensitizers. Inexpensive fluoroalkyl iodides were directly used as efficient fluoroalkylation reagents under very mild reaction conditions. The scope of this process was found to be general and broad, and both trifluoromethyl and perfluoroalkyl groups (‐C4F9, ‐C6F13, and ‐C8F17) were installed in excellent yields. Preliminary mechanistic studies suggest that visible‐light‐promoted intermolecular charge transfer within the naphtholate–fluoroalkyl iodide electron donor–acceptor (EDA) complex induces a single electron transfer in the absence of photocatalysts. 相似文献
13.
Dr. Ikuo Sasaki Jumpei Taguchi Hana Doi Prof. Dr. Hajime Ito Dr. Tatsuo Ishiyama 《化学:亚洲杂志》2016,11(9):1400-1405
A new process has been developed for the iridium(I)‐catalyzed vinylic C?H borylation of α,β‐unsaturated esters with bis(pinacolato)diboron (B2pin2). These reactions proceeded in octane at temperatures in the range of 80–120 °C to afford the corresponding alkenylboronic compounds in high yields with excellent regio‐ and stereoselectivities. The presence of an aryl ester led to significant improvements in the yields of the acyclic alkenylboronates. Crossover experiments involving deuterated substrates as well as a mixture of stereoisomers confirmed that this reaction proceeds via a 1,4‐addition/β‐hydride elimination mechanism. Notably, this reaction was also used to develop a one‐pot borylation/Suzuki–Miyaura cross‐coupling procedure. 相似文献
14.
Julia Pedroni Michele Boghi Dr. Tanguy Saget Prof. Dr. Nicolai Cramer 《Angewandte Chemie (International ed. in English)》2014,53(34):9064-9067
β‐Lactams are very important structural motifs because of their broad biological activities as well as their propensity to engage in ring‐opening reactions. Transition‐metal‐catalyzed C? H functionalizations have emerged as strategy enabling yet uncommon highly efficient disconnections. In contrast to the significant progress of Pd0‐catalyzed C? H functionalization for aryl–aryl couplings, related reactions involving the formation of saturated C(sp3)? C(sp3) bonds are elusive. Reported here is an asymmetric C? H functionalization approach to β‐lactams using readily accessible chloroacetamide substrates. Important aspects of this transformation are challenging C(sp3)? C(sp3) and strain‐building reductive eliminations to for the four‐membered ring. In general, the β‐lactams are formed in excellent yields and enantioselectivities using a bulky taddol phosphoramidite ligand in combination with adamantyl carboxylic acid as cocatalyst. 相似文献
15.
Stereoarrayed CF3‐Substituted 1,3‐Diols by Dynamic Kinetic Resolution: Ruthenium(II)‐Catalyzed Asymmetric Transfer Hydrogenation 下载免费PDF全文
Andrej Emanuel Cotman Dr. Dominique Cahard Dr. Barbara Mohar 《Angewandte Chemie (International ed. in English)》2016,55(17):5294-5298
CF3‐substituted 1,3‐diols were stereoselectively prepared in excellent enantiopurity and high yield from CF3‐substituted diketones by using an ansa‐ruthenium(II)‐catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. The intermediate mono‐reduced alcohol was also obtained in very high enantiopurity by applying milder reaction conditions. In particular, CF3C(O)‐substituted benzofused cyclic ketones underwent either a single or a double dynamic kinetic resolution during their reduction. 相似文献
16.
Yang Yuan Fu‐Peng Wu Jian‐Xing Xu Xiao‐Feng Wu 《Angewandte Chemie (International ed. in English)》2020,59(39):17055-17061
We report here a general four‐component synthetic procedure for the preparation of β‐boryl ketones and β‐boryl vinyl esters. Joint catalyzed by palladium and copper catalysts, borocarbonylative reaction between vinylarenes, aryl halides/triflates, B2Pin2, and carbon monoxide proceed successfully. A variety of synthetically useful β‐boryl ketones were synthesized in good to high yields by using aryl iodides as the substrates. It is noteworthy that when aryl triflates were applied as the starting materials, β‐boryl vinyl esters were synthesized in a similar manner and with broad functional group tolerance. A rational mechanism for this reaction was also proposed. 相似文献
17.
Enantioselective N‐Heterocyclic Carbene Catalysis by the Umpolung of α,β‐Unsaturated Ketones 下载免费PDF全文
Yuji Nakano Prof. Dr. David W. Lupton 《Angewandte Chemie (International ed. in English)》2016,55(9):3135-3139
N‐Heterocyclic carbene‐catalyzed formation of β‐anionic intermediates from enones has been employed in the enantioselective synthesis of 2‐aryl propionates. The reaction was achievable using a homochiral 4‐MeOC6H4 morpholinone catalyst allowing the first example of enantioselective catalysis by umpolung of α,β‐unsaturated ketones. The reaction is high yielding, and shows robustness with reasonable generality. A mechanism is proposed in which the enantiodetermining protonation is achieved using either hexafluoroisopropanol or the formed naphthol product. 相似文献
18.
Ken‐ichi Itoh Takamitsu Utsukihara Kenji Funayama Hiroshi Sakamaki Miyuki Kanamori T. Tomoyoshi Takahashi Yoshikazu Saitoh Masatoshi Matsushita Liangyou He Chikao Hashimoto Takashi Sugiyama C. Akira Horiuchi 《应用有机金属化学》2007,21(12):1029-1032
The reaction of α,β‐unsaturated ketones with cerium (IV) sulfate tetrahydrate [Ce(SO4)2·4H2O, CS] in acetic acid gave the corresponding β‐acetoxy ketones. In the case of 2‐cyclohexen‐1‐one with CS in acetic acid, benzobicyclo[2.2.2]octen‐2‐one was obtained. The reaction mechanism also was proposed. Moreover, we report the aromatization and esterification of (R)‐(?)‐carvone by CS in acetic acid. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
19.
In this paper, eight aryl substituted α, β‐unsaturated acyl hydrazides undergo efficient oxidation to α,β‐unsaturated acyl azo compounds using NaNO2‐acetic anhydride under mild conditions with excellent yields. 相似文献
20.
Catalytic Asymmetric Intramolecular Homologation of Ketones with α‐Diazoesters: Synthesis of Cyclic α‐Aryl/Alkyl β‐Ketoesters 下载免费PDF全文
Dr. Wei Li Fei Tan Xiaoyu Hao Gang Wang Yu Tang Prof. Dr. Xiaohua Liu Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2015,54(5):1608-1611
A catalytic asymmetric intramolecular homologation of simple ketones with α‐diazoesters was firstly accomplished with a chiral N,N′‐dioxide–Sc(OTf)3 complex. This method provides an efficient access to chiral cyclic α‐aryl/alkyl β‐ketoesters containing an all‐carbon quaternary stereocenter. Under mild conditions, a variety of aryl‐ and alkyl‐substituted ketone groups reacted with α‐diazoester groups smoothly through an intramolecular addition/rearrangement process, producing the β‐ketoesters in high yield and enantiomeric excess. 相似文献