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1.
Theoretical study on the reaction mechanisms and stereoselectivities of DABCO‐catalyzed Rauhut–Currier/cyclization reaction of methyl acrylate with 2‐benzoyl‐3‐phenyl‐acrylonitrile
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With the aid of density functional theory (DFT) calculations, we have investigated the mechanisms and stereoselectivities of the tandem cross Rauhut–Currier/cyclization reaction of methyl acrylate R1 with (E)‐2‐benzoyl‐3‐phenyl‐acrylonitrile R2 catalyzed by a tertiary amine DABCO. The results of the DFT calculations indicate that the favorable mechanism (mechanism A) includes three steps: the first step is the nucleophilic attack of DABCO on R1 to form intermediates Int1 and Int1‐1, the second step is the reaction of Int1 and Int1‐1 with R2 to generate intermediate Int2(SS,RR,SR&RS), and the last step is an intramolecular SN2 process to give the final product P(SS,RR,SR&RS) and release catalyst DABCO. The SN2 substitution is computed to be the rate‐determining step, whereas the second step is the stereoselectivity‐determining step. The present study may be helpful for understanding the reaction mechanism of similar tandem reactions. 相似文献
2.
Highly Enantioselective Intermolecular Cross Rauhut–Currier Reaction Catalyzed by a Multifunctional Lewis Base Catalyst
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Xuelin Dong Ling Liang Erqing Li Prof. Dr. You Huang 《Angewandte Chemie (International ed. in English)》2015,54(5):1621-1624
The highly enantioselective intermolecular cross Rauhut–Currier reaction of different active olefins catalyzed by a multifunctional chiral Lewis base was reported. The RC products were obtained in excellent yields (up to 98 %), high chemo‐ and enantioselectivity (up to 96 % ee). The reaction could be performed on a gram scale using 1 mol % of the multifunctional phosphine catalyst. 相似文献
3.
Jalal Z. A. Laloo Dr. Lydia Rhyman Prof. Dr. Ponnadurai Ramasami Prof. Dr. F. Matthias Bickelhaupt Dr. Abel de Cózar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4431-4439
The ion‐pair SN2 reactions of model systems MnFn?1+CH3Cl (M+=Li+, Na+, K+, and MgCl+; n=0, 1) have been quantum chemically explored by using DFT at the OLYP/6‐31++G(d,p) level. The purpose of this study is threefold: 1) to elucidate how the counterion M+ modifies ion‐pair SN2 reactivity relative to the parent reaction F?+CH3Cl; 2) to determine how this influences stereochemical competition between the backside and frontside attacks; and 3) to examine the effect of solvation on these ion‐pair SN2 pathways. Trends in reactivity are analyzed and explained by using the activation strain model (ASM) of chemical reactivity. The ASM has been extended to treat reactivity in solution. These findings contribute to a more rational design of tailor‐made substitution reactions. 相似文献
4.
Phosphine‐Catalyzed β,γ‐Umpolung Domino Reaction of Allenic Esters: Facile Synthesis of Tetrahydrobenzofuranones Bearing a Chiral Tetrasubstituted Stereogenic Carbon Center
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Dr. Shinobu Takizawa Kenta Kishi Dr. Yasushi Yoshida Steffen Mader Dr. Fernando Arteaga Arteaga Shoukou Lee Dr. Manabu Hoshino Prof. Dr. Magnus Rueping Prof. Dr. Makoto Fujita Prof. Dr. Hiroaki Sasai 《Angewandte Chemie (International ed. in English)》2015,54(51):15511-15515
An enantio‐, diastereo‐, regio‐, and chemoselective phosphine‐catalyzed β,γ‐umpolung domino reaction of allenic esters with dienones has been developed for the first time. The designed sequence, involving oxy‐Michael and Rauhut–Currier reactions, produced highly functionalized tetrahydrobenzofuranones, bearing a chiral tetrasubstituted stereogenic center, in up to 96 % ee. 相似文献
5.
Chiral Sulfinamide Bisphosphine Catalysts: Design,Synthesis, and Application in Highly Enantioselective Intermolecular Cross‐Rauhut–Currier Reactions
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Wei Zhou Xiao Su Mengna Tao Chaoze Zhu Dr. Qingjie Zhao Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2015,54(49):14853-14857
A novel type of highly efficient chiral sulfinamide bisphosphine catalysts (Wei‐Phos) were developed. These could be easily prepared from commercially available starting materials. Wei‐Phos has shown good performance in the very challenging intermolecular cross‐Rauhut–Currier reactions of vinyl ketones and 3‐acyl acrylates or 2‐ene‐1,4‐diones, leading to the R‐C products in high yields with up to 99 % ee under 2.5–5 mol% catalyst loading. The highly regio‐ and enantio‐selective cross‐Rauhut–Currier reactions of 2‐ene‐1,4‐diones and vinyl ketone have yet reported so far. 相似文献
6.
Xingxing Wu Liejin Zhou Rakesh Maiti Chengli Mou Lutai Pan Yonggui Robin Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(2):487-491
A carbene and sulfinate co‐catalyzed intermolecular Rauhut–Currier reaction between enals and nitrovinyl indoles is disclosed. The carbene catalyst activates the enal and the sulfinate co‐catalyst activates the nitrovinyl indole. Both activation processes are realized via the formation of covalent bonds between the catalysts and substrates to generate catalyst‐bound intermediates. The dual catalytic reaction affords azepino[1,2‐a]indole products with excellent stereoselectivity. Our study demonstrates the unique involvement of sulfinate as an effective nucleophilic catalyst in activating electron‐deficient alkenes for asymmetric reactions. This dual catalytic approach should also encourage future explorations of both sulfinate and carbene catalysts for new reactions. 相似文献
7.
Ion‐Pair SN2 Reaction of OH− and CH3Cl: Activation Strain Analyses of Counterion and Solvent Effects
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Jalal Z. A. Laloo Dr. Lydia Rhyman Dr. Olatz Larrañaga Prof. Dr. Ponnadurai Ramasami Prof. Dr. F. Matthias Bickelhaupt Dr. Abel de Cózar 《化学:亚洲杂志》2018,13(9):1138-1147
We have theoretically studied the non‐identity SN2 reactions of MnOH(n?1)+CH3Cl (M+=Li+, Na+, K+, and MgCl+; n=0, 1) in the gas phase and in THF solution at the OLYP/6‐31++G(d,p) level using polarizable continuum model (PCM) implicit solvation. We want to explore and understand the effect of the metal counterion M+ and solvation on the reaction profile and the stereoselectivity of these processes. To this end, we have explored the potential energy surfaces of the backside (SN2‐b) and frontside (SN2‐f) pathways. To explain the computed trends, we have carried out analyses with an extended activation strain model (ASM) of chemical reactivity that includes the treatment of solvation effects. 相似文献
8.
Enantioselective Organocatalytic Reduction of β‐Trifluoromethyl Nitroalkenes: An Efficient Strategy for the Synthesis of Chiral β‐Trifluoromethyl Amines
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Elisabetta Massolo Prof. Maurizio Benaglia Manuel Orlandi Dr. Sergio Rossi Giuseppe Celentano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3589-3595
An efficient organocatalytic stereoselective reduction of β‐trifluoromethyl‐substituted nitroalkenes, mediated by 3,5‐dicarboxylic ester‐dihydropyridines (Hantzsch ester type), has been successfully developed. A multifunctional thiourea‐based (S)‐valine derivative was found to be the catalyst of choice, promoting the reaction in up to 97 % ee. The methodology has been applied to a wide variety of substrates, leading to the formation of differently substituted precursors of enantiomerically enriched β‐trifluoromethyl amines. The mechanism of the reaction and the mode of action of the metal‐free catalytic species were computationally investigated; on the basis of DFT transition‐state (TS) analysis, a model of stereoselection was also proposed. 相似文献
9.
Discrepancies between chiroptical data from the literature and our determination of the structure of the title compounds (+)‐ 5 and (+)‐ 9a were resolved by an unambiguous assignment of their absolute configuration. Accordingly, the dextrorotatory cis‐3‐hydroxy esters have (3R,4R)‐ and the laevorotatory enantiomers (3S,4S)‐configuration. The final evidences were demonstrated on both enantiomers (+)‐ and (?)‐ 5 by biological reduction of 4 by bakers' yeast and stereoselective [RuII(binap)]‐catalyzed hydrogenations of 4 (Scheme 2), by the application of the NMR Mosher method on (+)‐ and (?)‐ 5 (Scheme 3), as well as by the transformation of (+)‐ 5 into a common derivative and chiroptical correlation (Scheme 4). 相似文献
10.
Starting from simple aromatic aldehydes and acetylfuran, (E)‐1‐(furan‐2‐yl)‐3‐arylprop‐2‐en‐1‐ones ( 2 ) were synthesized in high yields. Cyclopropanation of the C?C bond with trimethylsulfoxonium iodide (Me3SO+I?) furnished (furan‐2‐yl)(2‐arylcyclopropyl)methanones 3 in 90–97% yields. Selective conversion of cyclopropyl ketones to their (E)‐ and (Z)‐oxime ethers 5 and oxazaborolidine‐catalyzed stereoselective reduction of the C?N bond followed by separation of the formed diastereoisomers, furnished (2‐arylcyclopropyl)(furan‐2‐yl)methanamines 6 in optically pure form and high yield. Oxidation of the furan ring of (S,S,S)‐, (S,R,R)‐, (R,S,S)‐, and (R,R,R)‐ 6a afforded the four stereoisomers of α‐(2‐phenylcyclopropyl) glycine ( 1a ). 相似文献
11.
Wei Zhou Xiao Su Mengna Tao Chaoze Zhu Qingjie Zhao Junliang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(49):15066-15070
A novel type of highly efficient chiral sulfinamide bisphosphine catalysts (Wei‐Phos) were developed. These could be easily prepared from commercially available starting materials. Wei‐Phos has shown good performance in the very challenging intermolecular cross‐Rauhut–Currier reactions of vinyl ketones and 3‐acyl acrylates or 2‐ene‐1,4‐diones, leading to the R‐C products in high yields with up to 99 % ee under 2.5–5 mol% catalyst loading. The highly regio‐ and enantio‐selective cross‐Rauhut–Currier reactions of 2‐ene‐1,4‐diones and vinyl ketone have yet reported so far. 相似文献
12.
Reinhold Zimmer Vjekoslav Dekaris Markus Knauer Luise Schefzig Hans-Ulrich Reissig 《合成通讯》2013,43(6):1012-1026
The Mukaiyama aldol reaction of 2-styryl-oxazole-4-carbaldehyde (1) as model substrate with S-ketene silyl acetal 2 catalyzed by poly(ethylene glycol)-supported binaphthyl-derived chiral titanium(IV) complexes afforded the corresponding aldol product in good to excellent yields and enantioselectivities up to 94% ee. The chemical yields and/or the enantioselectivities are enhanced by generating the active catalyst from Ti(OiPr)4, polymer-supported ligands (R)-6 or (R)-8, and chiral or achiral promoters. Pyrrolidine derivative (S)-13 and trifluoromethyl-substituted phenol 12 are the most efficient additives found. 相似文献
13.
A Stereoselective Aldol Approach for the Total Syntheses of Two 6‐Alkylated 2H‐Pyran‐2‐ones
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Singanaboina Rajaram Dasari Ramesh Udugu Ramulu Peddikotla Prabhakar Yenamandra Venkateswarlu 《Helvetica chimica acta》2014,97(1):112-121
A simple and highly efficient stereoselective total synthesis of the 6‐alkylated pyranones (6R)‐6‐[(1E,4R,6R)‐4,6‐dihydroxy‐10‐phenyldec‐1‐en‐1‐yl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 1 ) and (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one ( 2 ) was developed using Crimmins' aldol reaction, SmI2 reduction, Grubbs‐II‐catalyzed olefin cross‐metathesis, and Still's modified Horner? Wadsworth? Emmons reaction. 相似文献
14.
Biswanath Das Katta Venkateswarlu Maddeboina Krishnaiah Harish Holla Anjoy Majhi 《Helvetica chimica acta》2006,89(7):1417-1421
Treatment of Baylis–Hillman adducts 1 with bromo(dimethyl)sulfonium bromide, Br(Me2)S+Br?, in MeCN was found to stereoselectively afford (Z)‐ and (E)‐allyl bromides 2 . The reaction is rapid at room temperature, high‐yielding, and highly stereoselective. 相似文献
15.
Competitive Gold‐Promoted Meyer–Schuster and oxy‐Cope Rearrangements of 3‐Acyloxy‐1,5‐enynes: Selective Catalysis for the Synthesis of (+)‐(S)‐γ‐Ionone and (−)‐(2S,6 R)‐cis‐γ‐Irone
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Dr. Serena Bugoni Dr. Valentina Merlini Dr. Alessio Porta Dr. Sylvain Gaillard Prof. Giuseppe Zanoni Prof. Dr. Steven P. Nolan Prof. Giovanni Vidari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14068-14074
We report a simple, highly stereoselective synthesis of (+)‐(S)‐γ‐ionone and (‐)‐(2S,6R)‐cis‐γ‐irone, two characteristic and precious odorants; the latter compound is a constituent of the essential oil obtained from iris rhizomes. Of general interest in this approach are the photoisomerization of an endo trisubstituted cyclohexene double bond to an exo vinyl group and the installation of the enone side chain through a [(NHC)AuI]‐catalyzed Meyer–Schuster‐like rearrangement. This required a careful investigation of the mechanism of the gold‐catalyzed reaction and a judicious selection of reaction conditions. In fact, it was found that the Meyer–Schuster reaction may compete with the oxy‐Cope rearrangement. Gold‐based catalytic systems can promote either reaction selectively. In the present system, the mononuclear gold complex [Au(IPr)Cl], in combination with the silver salt AgSbF6 in 100:1 butan‐2‐one/H2O, proved to efficiently promote the Meyer–Schuster rearrangement of propargylic benzoates, whereas the digold catalyst [{Au(IPr)}2(μ‐OH)][BF4] in anhydrous dichloromethane selectively promoted the oxy‐Cope rearrangement of propargylic alcohols. 相似文献
16.
José Luis García Ruano Prof. Ana M. Martín‐Castro Prof. Francisco Tato Dr. Esther Torrente Ana M. Poveda Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(21):6317-6325
Enantiomerically enriched α,α‐disubstituted phenylacetonitriles have been readily prepared by stereoselective quaternization of 2‐alkyl‐2‐[2‐(p‐tolylsulfinyl)phenyl]acetonitriles with different alkylating electrophiles in the presence of bases. The use of potassium hexamethyldisilazane (KHMDS)/[18]crown‐6 ether and NHMDS with alkyl halides afforded S,SS and R,SS diastereoisomers, respectively, in high enantiomeric purities, thus providing stereodivergent processes for synthesizing both isomers. The dependence of the stereochemical course of the reactions on the experimental conditions (mainly on the counterion) has been rationalized by assuming a planar or pyramidal structure for the benzylic carbanions. This hypothesis has been supported by NMR spectroscopic studies, which permit one to assign a chelated pyramidal structure to the sodium benzylic carbanions and an almost planar naked carbanionic structure to the potassium benzylic carbanions generated in the presence of [18]crown‐6 ether. 相似文献
17.
Asymmetric Pentafulvene Carbometalation—Access to Enantiopure Titanocene Dichlorides of Biological Relevance
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Dr. Melchior Cini Prof. Dr. Tracey D. Bradshaw Prof. Dr. Simon Woodward Dr. William Lewis 《Angewandte Chemie (International ed. in English)》2015,54(47):14179-14182
Unprecedented asymmetric copper‐catalyzed addition of ZnEt2 (ZnBu2) to the exocyclic C?C bond of pentafulvenes C5H4(?CHAr) (Ar=2‐MeOPh and related species) results in enantiomerically enriched (up to 93:7 e.r.) cyclopentadienyl ligands (C5H4CHEtAr; abbreviated CpR). Copper catalyst promotion with both chiral phosphoramidite ligands and a phosphate additive is vital in realizing both acceptable enantioselectivities and reaction rates. Enantiomeric CpR2TiCl2 complexes have been prepared; the (S,S) isomer is twice as active towards pancreatic, breast, and colon cancer cell lines as its (R,R) enantiomer at 24 h. 相似文献
18.
Stereoselectivity of reductive amination of (R)-1-hydroxy-1-phenylpropan-2-one by methylamine was studied. From the four isomers possible, only two are produced by this
reaction. These are marked as (−)-(1R,2S)-ephedrine (desired product) and (+)-(1S,2R)-ephedrine. The reaction stereoselectivity depends both on the type of the catalyst and reaction conditions. The most suitable
type is the supported platinum. However, this catalyst rapidly deactivates. With a decreasing activity of Pt catalyst, the
stereoselectivity decreases. It is also decreased during the production of the second liquid phase (water) in the reaction
mixture. 相似文献
19.
Nandini Savoo Jalal Z. A. Laloo Lydia Rhyman Ponnadurai Ramasami F. Matthias Bickelhaupt Jordi Poater 《Journal of computational chemistry》2020,41(4):317-327
We have computationally studied the bimolecular nucleophilic substitution (SN2) reactions of MnNH2(n−1) + CH3Cl (M+ = Li+, Na+, K+, and MgCl+; n = 0, 1) in the gas phase and in tetrahydrofuran solution at OLYP/6-31++G(d,p) using polarizable continuum model implicit solvation. We wish to explore and understand the effect of the metal counterion M+ and of solvation on the reaction profile and the stereochemical preference, that is, backside (SN2-b) versus frontside attack (SN2-f). The results were compared to the corresponding ion-pair SN2 reactions involving F− and OH− nucleophiles. Our analyses with an extended activation strain model of chemical reactivity uncover and explain various trends in SN2 reactivity along the nucleophiles F−, OH−, and , including solvent and counterion effects. © 2019 Wiley Periodicals, Inc. 相似文献
20.
Fei Ye Dr. Zhan‐Jiang Zheng Wen‐Hui Deng Long‐Sheng Zheng Dr. Yuan Deng Prof. Chun‐Gu Xia Prof. Dr. Li‐Wen Xu 《化学:亚洲杂志》2013,8(9):2242-2253
In this work, we have successfully synthesized a new family of chiral Schiff base–phosphine ligands derived from chiral binaphthol (BINOL) and chiral primary amine. The controllable synthesis of a novel hexadentate and tetradentate N,O,P ligand that contains both axial and sp3‐central chirality from axial BINOL and sp3‐central primary amine led to the establishment of an efficient multifunctional N,O,P ligand for copper‐catalyzed conjugate addition of an organozinc reagent. In the asymmetric conjugate reaction of organozinc reagents to enones, the polymer‐like bimetallic multinuclear Cu? Zn complex constructed in situ was found to be substrate‐selective and a highly excellent catalyst for diethylzinc reagents in terms of enantioselectivity (up to >99 % ee). More importantly, the chirality matching between different chiral sources, C2‐axial binaphthol and sp3‐central chiral phosphine, was crucial to the enantioselective induction in this reaction. The experimental results indicated that our chiral ligand (R,S,S)‐ L1 ‐ and (R,S)‐ L4 ‐based bimetallic complex catalyst system exhibited the highest catalytic performance to date in terms of enantioselectivity and conversion even in the presence of 0.005 mol % of catalyst (S/C=20 000, turnover number (TON)=17 600). We also studied the tandem silylation or acylation of enantiomerically enriched zinc enolates that formed in situ from copper‐ L4 ‐complex‐catalyzed conjugate addition, which resulted in the high‐yield synthesis of chiral silyl enol ethers and enoacetates, respectively. Furthermore, the specialized structure of the present multifunctional N,O,P ligand L1 or L4 , and the corresponding mechanistic study of the copper catalyst system were investigated by 31P NMR spectroscopy, circular dichroism (CD), and UV/Vis absorption. 相似文献