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Patrick G. Isenegger Dr. Florian Bächle Prof. Dr. Andreas Pfaltz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17595-17599
An efficient protocol for the evaluation of catalysts for the asymmetric Morita–Baylis–Hillman (MBH) reaction was developed. By mass spectrometric back‐reaction screening of quasi‐enantiomeric MBH products, an efficient bifunctional phosphine catalyst was identified that outperforms literature‐known catalysts in the MBH reaction of methyl acrylate with aldehydes. The close match between the selectivities measured for the forward and back reaction and kinetic measurements provided strong evidence that the aldol step and not the subsequent proton transfer is rate‐ and enantioselectivity‐determining. 相似文献
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Filipe J. S. Duarte Dipl.‐Chem. Eurico J. Cabrita Prof. Dr. Gernot Frenking Prof. Dr. A. Gil Santos Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(7):1734-1746
A rationalization of stereoselectivity : The mechanisms of proline‐catalyzed and imidazole‐co‐catalyzed intramolecular Baylis–Hillman reactions have been studied by using density functional theory methods. The computational data has allowed us to rationalize the experimental outcome, validating some of the mechanistic steps proposed in the literature, as well as to propose new ones that considerably change and improve our understanding of the full reaction path (see scheme).
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Jian‐Fen Fan Chun‐Hong Yang Liang‐Jun He 《International journal of quantum chemistry》2009,109(6):1311-1321
B3LYP/6‐311++G** calculations have been carried out to study the role of methanol solvent in the trimethylamine‐catalyzed Morita‐Baylis‐Hillman reaction between acraldehyde and formaldehyde with CPCM solvent method and supramolecular model with one explicit CH3OH solvent molecule, respectively. The optimized geometries and energies of the reactant complexes, intermediates, transition states, and products of the two reaction channels (corresponding to the scenarios of syn‐ and anti‐acraldehyde, respectively) were obtained, and the relative energy profiles were completed. The results reveal that CH3OH solvent molecules can stabilize the zwitterionic intermediates and largely reduce the barrier of H transfer process by taking part in the formation of the transition state in this process. C? C bond formation step is the rate‐determining step of the whole reaction cycle. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
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Shlomy Arava Sourav K. Santra Gulab K. Pathe Raja Kapanaiah Alex M. Szpilman 《Angewandte Chemie (International ed. in English)》2020,59(35):15171-15175
Herein we report on the umpolung of Morita–Baylis–Hillman type intermediates and application to the α‐functionalization of enone C?H bonds. This reaction gives direct access to α‐chloro‐enones, 1,2‐diketones and α‐tosyloxy‐enones. The latter are important intermediates for cross‐coupling reaction and, to the best of our knowledge, cannot be made in a single step from enones in any other way. The proposed mechanism is supported by spectroscopic studies. The key initial step involves conjugate attack of an amine (DABCO or pyridine), likely assisted by hypervalent iodine acting as a Lewis acid leading to formation of an electrophilic β‐ammonium‐enolonium species. Nucleophilic attack by acetate, tosylate, or chloride anion is followed by base induced elimination of the ammonium species to give the noted products. Hydrolysis of α‐acetoxy‐enones lead to formation of 1,2‐diketones. The α‐tosyl‐enones participate in Negishi coupling reactions under standard conditions. 相似文献
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Bidyut Kumar Senapati Dr. Geum‐Sook Hwang Prof. Dr. Sungil Lee Do Hyun Ryu Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(24):4398-4401
A catalytic route toward chiral Morita–Baylis–Hillman esters by asymmetric coupling between α,β‐acetylenic esters, aldehydes, and trimethylsilyl iodide has been developed (see scheme). The reaction proceeds with high to excellent enantioselectivities, and the products can be transformed into β‐branched derivatives in a single step and with excellent retention of configuration. TMS=trimethylsilyl
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Organocatalytic One‐Pot Synthesis of Highly Substituted Pyridazines from Morita–Baylis–Hillman Carbonates and Diazo Compounds 下载免费PDF全文
Zhongkai Tang Prof. Dr. Hongwen Hu Prof. Dr. Chengjian Zhu Prof. Dr. Yixiang Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2454-2458
A biologically inspired organocatalytic one‐pot synthesis of highly functionalized pyridazines, which are ubiquitous structural units in a number of biologically active compounds, has been developed by starting from readily available diazo compounds and Morita–Baylis–Hillman (MBH) carbonates. Under mild reaction conditions, this synthetic route tolerated significant substrate variation to deliver a broad range of substituted products, including CF3‐substituted pyridazines derivatives. Moreover, the introduction of trifluoromethyl groups into the ring of pyridazine could be completed conveniently from 2,2,2‐trifluorodiazoethane. 相似文献
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Hai‐Lei Cui Jing Peng Xin Feng Wei Du Kun Jiang Ying‐Chun Chen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(7):1574-1577
The first highly enantioselective allylic–allylic alkylation of α,α‐dicyanoalkenes and Morita–Baylis–Hillman carbonates by dual catalysis of (DHQD)2AQN and (S)‐BINOL has been investigated. Excellent stereoselectivities have been achieved for a broad spectrum of substrates (d.r. > 99:1, up to 99 % ee). The multifunctional allylic products could be efficiently converted to a range of complex chiral cyclic frameworks. EWG=electron‐withdrawing group, (DHQD)2AQN=hydroquinidine (anthraquinone‐1,4‐diyl) diether, (S)‐BINOL =(S)‐(?)‐1,1′‐bi‐2‐naphthol.
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Novel Organocatalytic Activation of Unmodified Morita–Baylis–Hillman Alcohols for the Synthesis of Bicyclic α‐Alkylidene‐Ketones 下载免费PDF全文
Dr. Julian Stiller Dorota Kowalczyk Dr. Hao Jiang Prof. Dr. Karl Anker Jørgensen Dr. Łukasz Albrecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13108-13112
The organocatalytic activation of Morita–Baylis–Hillman alcohols via H‐bonding‐iminium‐ion formation is demonstrated for the first time. This activation strategy enables the Morita‐Baylis–Hillman alcohols to undergo a formal SN2′ reaction. In combination with the well‐established enamine reactivity, this creates a new reactivity pattern. The application of this new activation mode for the synthesis of bicyclic α‐alkylidene‐ketones is demonstrated. The developed reaction sequence proceeds efficiently affording nature‐inspired target products with four contiguous stereogenic centers in a highly stereoselective manner. 相似文献
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The saccharide‐based chiral bifunctional thiourea‐phosphines were developed as chiral organocatalysts for the intramolecular Morita‐Baylis‐Hillman reaction of ω‐formyl‐enones. With only 2 mol% of thiourea‐phosphine catalyst 3c , chiral functionalized cyclohexenes were achieved under mild reaction conditions with excellent yields and enantioselectivities. 相似文献
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Elusive Reaction Intermediates in Solution Explored by ESI‐MS: Reverse Periscope for Mechanistic Investigations 下载免费PDF全文
Dr. Claudio Iacobucci Dr. Samantha Reale Prof. Francesco De Angelis 《Angewandte Chemie (International ed. in English)》2016,55(9):2980-2993
Just as periscopes allow a submarine to visually search for objects above the surface of the sea, in a reversed periscope fashion electrospray mass spectrometry (ESI‐MS) can analyze the compounds at the gas phase/liquid phase interface for chemical entities which may exist in solution. The challenge is the identification and structural characterization of key elusive reaction intermediates in chemical transformations, intermediates which are able to explain how chemical processes occur. This Minireview summarizes recent selected publications on the use of ESI‐MS techniques for studying solution intermediates of homogeneous chemical reactions. 相似文献
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Francesca Nunzi Dr. Antonio Sgamellotti Prof. Filippo De Angelis Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(16):4182-4189
Breaking barriers : In agreement with experimental evidence, it was found by means of high‐level DFT calculations that the Cr(CO)3 metal fragment considerably reduces the reaction energy barrier—for both the concerted and stepwise reaction mechanisms (see graphic)—of the Diels–Alder reaction of butadiene on (5,5) carbon nanotubes.
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Dr. Sílvia Osuna Dr. Alpay Dermenci Prof. Scott J. Miller Prof. K. N. Houk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14245-14253
The stereoselective Rauhut–Currier (RC) reaction catalyzed by a cysteine derivative has been explored computationally with density functional theory (M06‐2X). Both methanethiol and a chiral cysteine derivative were studied as nucleophiles. The complete reaction pathway involves rate‐determining elimination of the thiol catalyst from the Michael addition product. The stereoselective Rauhut–Currier reaction, catalyzed by a cysteine derivative as a nucleophile, has also been studied in detail. This reaction was experimentally found to be extremely sensitive to the reaction conditions, such as the number of water equivalents and the effect of potassium counterion. The E1cB process for catalyst elimination has been explored computationally for the eight possible stereoisomers. The effect of explicit water solvation and the presence of counterion (either K+ or Na+) has been studied for the lowest energy enantiomer pair (1S, 2R, 3S)/(1R, 2S, 3R). 相似文献
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Senmiao Xu Dr. Zheng Wang Prof. Dr. Yuxue Li Prof. Dr. Xumu Zhang Prof. Dr. Haiming Wang Kuiling Ding Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(10):3021-3035
The mechanism of the chiral phosphoric acid catalyzed Baeyer–Villiger (B–V) reaction of cyclobutanones with hydrogen peroxide was investigated by using a combination of experimental and theoretical methods. Of the two pathways that have been proposed for the present reaction, the pathway involving a peroxyphosphate intermediate is not viable. The reaction progress kinetic analysis indicates that the reaction is partially inhibited by the γ‐lactone product. Initial rate measurements suggest that the reaction follows Michaelis–Menten‐type kinetics consistent with a bifunctional mechanism in which the catalyst is actively involved in both carbonyl addition and the subsequent rearrangement steps through hydrogen‐bonding interactions with the reactants or the intermediate. High‐level quantum chemical calculations strongly support a two‐step concerted mechanism in which the phosphoric acid activates the reactants or the intermediate in a synergistic manner through partial proton transfer. The catalyst simultaneously acts as a general acid, by increasing the electrophilicity of the carbonyl carbon, increases the nucleophilicity of hydrogen peroxide as a Lewis base in the addition step, and facilitates the dissociation of the OH group from the Criegee intermediate in the rearrangement step. The overall reaction is highly exothermic, and the rearrangement of the Criegee intermediate is the rate‐determining step. The observed reactivity of this catalytic B–V reaction also results, in part, from the ring strain in cyclobutanones. The sense of chiral induction is rationalized by the analysis of the relative energies of the competing diastereomeric transition states, in which the steric repulsion between the 3‐substituent of the cyclobutanone and the 3‐ and 3′‐substituents of the catalyst, as well as the entropy and solvent effects, are found to be critically important. 相似文献
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Liu Liu Shuangyan Zhang Dr. Hu Chen Ye Lv Dr. Jun Zhu Prof. Dr. Yufen Zhao 《化学:亚洲杂志》2013,8(11):2592-2595
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Liang‐Hua Zou Dr. Adam Johannes Johansson Dr. Erik Zuidema Prof. Dr. Carsten Bolm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8144-8152
An efficient catalytic system for Sonogashira–Hagihara‐type reactions displaying ligand acceleration in the copper‐catalyzed formation of C(sp2)? C(sp) bonds is described. The structure of the ligand plays a key role for the coupling efficiency. Various copper sources show excellent catalytic activity, even in sub‐mol % quantities. A wide variety of substituents is tolerated in the substrates. Mechanistic details have been revealed by kinetic measurements and DFT calculations. 相似文献
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Yangxue Liu Sultan Ahmed Xiao‐Yan Qin Hossein Rouh Guanzhao Wu Guigen Li Bo Jiang 《化学:亚洲杂志》2020,15(7):1125-1131
An effective chiral GAP methodology for preparing α‐aminomethyl enaminones through a (R)‐CSA‐catalyzed asymmetric aza‐Baylis‐Hillman reaction is reported. Excellent yields and high diastereoselectivity could be obtained under mild conditions and convenient GAP techniques. The confirmations of the absolute configuration of N‐phosphonyl imine and chiral enaminone by X‐ray diffraction provides an explicit explanation of the chirality mechanism for GAP chemistry. 相似文献