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1.
Enantioselective Desymmetrization of Cyclobutanones Enabled by Synergistic Palladium/Enamine Catalysis 下载免费PDF全文
Meng Wang Jun Chen Zongjia Chen Changxu Zhong Prof. Dr. Ping Lu 《Angewandte Chemie (International ed. in English)》2018,57(10):2707-2711
The enantioselective intramolecular α‐arylation of cyclobutanones has been established by combining palladium and enamine catalyst systems. Two different enantioselective control strategies have been developed for cyclobutanone substrates bearing O‐ or N‐tethered aryl bromides. Further synthetic applications are also reported. 相似文献
2.
Dr. María D. Díaz‐de‐Villegas Dr. José A. Gálvez Dr. Ramón Badorrey Dr. M. Pilar López‐Ram‐de‐Víu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(44):13920-13935
Desymmetrization of diols is a powerful tool to the synthesis of chiral building blocks. Among the different approaches to perform discrimination between both enantiotopic hydroxyl groups, the organocatalytic approach has gained importance in the last years. A diverse range of organocatalysts has been used to efficiently promote this enantioselective transformation and this Minireview examines the different contributions in this field. 相似文献
3.
Highly Enantioselective Construction of Tricyclic Derivatives by the Desymmetrization of Cyclohexadienones 下载免费PDF全文
Sandra del Pozo Dr. Alejandro Parra Dr. Sergio Díaz‐Tendero Dr. Rubén Mas‐Ballesté Dr. Silvia Cabrera Dr. José Alemán 《Angewandte Chemie (International ed. in English)》2014,53(31):8184-8189
The asymmetric synthesis of tricyclic compounds by the desymmetrization of cyclohexadienones is presented. The reaction tolerated a large variety of substituents at different positions of the cyclohexadienone, and heterocyclic rings of different sizes were accessible. Density functional theory calculations showed that the reaction proceeds through an asynchronous [4+2] cycloaddition. 相似文献
4.
Enantioselective Desymmetrization of Prochiral Cyclohexanones by Organocatalytic Intramolecular Michael Additions to α,β‐Unsaturated Esters 下载免费PDF全文
Adam D. Gammack Yamagata Dr. Swarup Datta Kelvin E. Jackson Linus Stegbauer Dr. Robert S. Paton Prof. Dr. Darren J. Dixon 《Angewandte Chemie (International ed. in English)》2015,54(16):4899-4903
A new catalytic asymmetric desymmetrization reaction for the synthesis of enantioenriched derivatives of 2‐azabicyclo[3.3.1]nonane, a key motif common to many alkaloids, has been developed. Employing a cyclohexanediamine‐derived primary amine organocatalyst, a range of prochiral cyclohexanone derivatives possessing an α,β‐unsaturated ester moiety linked to the 4‐position afforded the bicyclic products, which possess three stereogenic centers, as single diastereoisomers in high enantioselectivity (83–99 % ee) and in good yields (60–90 %). Calculations revealed that stepwise C? C bond formation and proton transfer via a chair‐shaped transition state dictate the exclusive endo selectivity and enabled the development of a highly enantioselective primary amine catalyst. 相似文献
5.
Stereocontrol of All‐Carbon Quaternary Centers through Enantioselective Desymmetrization of Meso Primary Diols by Organocatalyzed Acyl Transfer 下载免费PDF全文
Christèle Roux Dr. Mathieu Candy Prof. Dr. Jean‐Marc Pons Dr. Olivier Chuzel Dr. Cyril Bressy 《Angewandte Chemie (International ed. in English)》2014,53(3):766-770
The symmetry breaking of meso primary diols bearing a tetrahydropyran ring was employed, using catalytic asymmetric acyl transfer, to control all‐carbon quaternary stereocenters. The planar chiral Fu DMAP catalyst was used in this reaction to reach a high degree of enantioselectivity (up to 97:3 e.r.) through a synergic effect combining a desymmetrization step and a kinetic resolution. Moreover, a beneficial effect was exhibited by C6F6 solvent, yielding the first example of an organocatalyzed asymmetric acyl transfer. The desymmetrized monoesters were then used to obtain, after a straightforward ring opening sequence, complex polyketide building blocks bearing all‐carbon quaternary stereocenters. 相似文献
6.
Ren-Zhe Li Hua Tang Dr. Ke R. Yang Li-Qiang Wan Xia Zhang Jie Liu Zhengyan Fu Prof. Dawen Niu 《Angewandte Chemie (International ed. in English)》2017,56(25):7213-7217
A copper/borinic acid dual catalytic reaction enabled the enantioselective propargylation of aliphatic polyols. Readily available reagents and catalysts were used in this transformation, which displayed good to excellent chemo- and stereoselectivity for a broad array of substrates. The method was also applicable to the desymmetrization of meso 1,2-diols to furnish products with three stereogenic centers and a terminal alkyne group in one operation. 相似文献
7.
Dr. Chenikkayala Siva Sankara Dr. Shweta Bhagat Dr. Ajeet Chandra Prof. Dr. Irishi N. N. Namboothiri 《European journal of organic chemistry》2023,26(15):e202300069
An enantioselective desymmetrization of curcumins with 3-olefinic oxindoles involving a cascade double-Michael addition strategy provides direct access to spirocyclohexanone-oxindoles with complete regio- and diastereoselectivities and excellent enantioselectivities, besides good to excellent yields. The products possess three contiguous chiral centers and multiple reactive functionalities. The observed selectivities were rationalized by transitions state energy calculations at B3LYP//6-31g(d) level of DFT. 相似文献
8.
Sandra Rodriguez Uxue Uria Efraim Reyes Luisa Carrillo Toms Tejero Pedro Merino Jose L. Vicario 《Angewandte Chemie (International ed. in English)》2020,59(17):6780-6784
The enantioselective synthesis of tropanols has been accomplished through chiral phosphoric acid catalyzed pseudotransannular ring opening of 1‐aminocyclohept‐4‐ene‐derived epoxides. The reaction proceeds together with the desymmetrization of the starting material and leads to the direct formation of the 8‐azabicyclo[3.2.1]octane scaffold with excellent stereoselectivity. The synthetic applicability of the reaction was demonstrated by the enantioselective synthesis of the two natural products (?)‐α‐tropanol and (+)‐ferruginine. 相似文献
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10.
Dr. Konstantin I. Galkin Bogdan Ya. Karlinskii Dr. Alexander Yu. Kostyukovich Dr. Evgeniy G. Gordeev Prof. Dr. Valentine P. Ananikov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(39):8567-8571
This work reveals ambident nucleophilic reactivity of imidazolium cations towards carbonyl compounds at the C2 or C4 carbene centers depending on the steric properties of the substrates and reaction conditions. Such an adaptive behavior indicates the dynamic nature of organocatalysis proceeding via a covalent interaction of imidazolium carbenes with carbonyl substrates and can be explained by generation of the H-bonded ditopic carbanionic carbenes. 相似文献
11.
12.
Palladium‐Catalyzed Desymmetrization of Silacyclobutanes with Alkynes to Silicon‐Stereogenic Silanes: A Density Functional Theory Study 下载免费PDF全文
Jin Zhang Jin‐Zhou Xu Dr. Zhan‐Jiang Zheng Dr. Zheng Xu Dr. Yu‐Ming Cui Dr. Jian Cao Prof. Dr. Li‐Wen Xu 《化学:亚洲杂志》2016,11(20):2867-2875
The palladium‐catalyzed desymmetrization of silacyclobutanes using electron‐deficient alkynes proceeds with high enantioselectivity in the presence of a chiral P ligand; this provides a facile approach for the synthesis of novel silicon‐stereogenic silanes. In this work, we used hybrid density functional theory (DFT) to elucidate the mechanism of the palladium‐catalyzed desymmetrization of silacyclobutanes with dimethyl acetylenedicarboxylate. Full catalytic cycle including two different initiation modes that were proposed to be a possible initial step to the formation of the 1‐pallada‐2‐silacyclopentane/alkyne intermediate—the oxidative addition of the palladium complex to the silacyclobutane Si?C bond (cycle MA) or coordination of the Pd0 complex with the alkyne C≡C bond (cycle MB)—have been studied. It was found that the ring‐expansion reaction began with cycle MB is energetically more favorable. The formation of a seven‐membered metallocyclic PdII intermediate was found to be the rate‐determining step, whereas the enantioselectivity‐determining step, oxidative addition of silacyclobutane to the three‐membered metallocyclic PdII intermediate, was found to be quite sensitive to the steric repulsion between the chiral ligand and silacyclobutane. 相似文献
13.
Termaten AT Schakel M Ehlers AW Lutz M Spek AL Lammertsma K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3577-3582
The novel phosphinidene complex [Cp*(NHC)Ir=PMes*] (3; NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) was prepared in high yield from [Cp*(NHC)IrCl(2)] (2) and [LiPHMes*].3 THF. It represents the first example of an NHC ligated transition metal phosphinidene complex. The X-ray crystal structure for 3 is also reported. DFT calculations on the N-heterocyclic carbene containing parent complexes [Cp(NHC)Ir=E] (E=PH, NH, CH(2)) show that the NHC ligand acts as good sigma-donor/weak pi-acceptor ligand and forms strong Ir-C(NHC) single bonds. The Ir=E double bonds result from strong triplet-triplet interactions between [Cp(NHC)Ir] and E. 相似文献
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15.
Albert Farre Kaline Soares Rachel A. Briggs Dr. Angelica Balanta Dr. David M. Benoit Dr. Amadeu Bonet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17552-17556
The generation of in situ sp2–sp3 diboron adducts has revolutionised the synthesis of organoboranes. Organocatalytic diboration reactions have represented a milestone in terms of unpredictable reactivity of these adducts. However, current methodologies have limitations in terms of substrate scope, selectivity and functional group tolerance. Here a new methodology based on the use of simple amines as catalyst is reported. This methodology provides a completely selective transformation overcoming current substrate scope and functional/protecting group limitations. Mechanistic studies have been included in this report. 相似文献
16.
Paul M. Zimmerman Ankan Paul Dr. Zhiyong Zhang Dr. Charles B. Musgrave Prof. 《Angewandte Chemie (International ed. in English)》2009,48(12):2201-2205
Enders' N‐heterocyclic carbene (NHC) dehydrogenates ammonia–borane with a relatively low barrier, producing NH2BH2 and NHC–(H)2. The nickel NHC catalyst present in the reaction media can activate the NHC–(H)2 produced to regenerate the free NHC and release H2. The release of free NHC enables further dehydrogenation of ammonia–borane.
17.
Enantioselective Synthesis of Tertiary Propargylic Alcohols under N‐Heterocyclic Carbene Catalysis 下载免费PDF全文
Eduardo Sánchez‐Díez Dr. Maitane Fernández Dr. Uxue Uria Prof. Efraim Reyes Prof. Luisa Carrillo Prof. Jose L. Vicario 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8384-8388
A straightforward procedure to carry out the enantioselective benzoin reaction between aldehydes and ynones by employing a chiral N‐heterocyclic carbene (NHC) as catalyst was developed. Under the optimized reaction conditions, these ynones undergo a clean and selective 1,2‐addition with the catalytically generated Breslow intermediate, not observing any byproduct arising from competitive Stetter‐type reactivity. This procedure allows the preparation of tertiary alkynyl carbinols as highly enantioenriched materials, which have the remarkable potential to be used as chiral building blocks in organic synthesis. 相似文献
18.
Dr. David L. Cramer Srikrishna Bera Prof. Dr. Armido Studer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7403-7407
The utility of oxidative NHC catalysis for both the regioselective and chemoselective functionalization of carbohydrates is explored. Chiral NHCs allow for the highly regioselective oxidative esterification of various carbohydrates using aldehydes as acylation precursors. The transformation was also shown to be amenable to both cis/trans diol isomers, free amino groups, and selective for specific sugar epimers in competition experiments. Efficiency and regioselectivity of the acylation can be improved upon using two different NHC catalysts that act cooperatively. The potential of the method is documented by the regioselective acylation of an amino‐linked neodisaccharide. 相似文献
19.
Dr. Suman De Sarkar Anup Biswas Ramesh C. Samanta Prof. Dr. Armido Studer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4664-4678
This Concept article discusses the potential of oxidative carbene catalysis in synthesis and comprehensively covers pioneering studies as well as recent developments. Oxidative carbene catalysis can be conducted by using inorganic and organic oxidants. Applications in cascade processes, in enantioselective catalysis, and also in natural product synthesis are discussed. 相似文献
20.
Marion N Carlqvist P Gealageas R de Frémont P Maseras F Nolan SP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(22):6437-6451
The [(NHC)AuI]-catalyzed (NHC=N-heterocyclic carbene) formation of alpha,beta-unsaturated carbonyl compounds (enones and enals) from propargylic acetates is described. The reactions occur at 60 degrees C in 8 h in the presence of an equimolar mixture of [(NHC)AuCl] and AgSbF6 and produce conjugated enones and enals in high yields. Optimization studies revealed that the reaction is sensitive to the solvent, the NHC, and, to a lesser extent, to the silver salt employed, leading to the use of [(ItBu)AuCl]/AgSbF6 in THF as an efficient catalytic system. This transformation proved to have a broad scope, enabling the stereoselective formation of (E)-enones and -enals with great structural diversity. The effect of substitution at the propargylic and acetylenic positions has been investigated, as well as the effect of aryl substitution on the formation of cinnamyl ketones. The presence or absence of water in the reaction mixture was found to be crucial. From the same phenylpropargyl acetates, anhydrous conditions led to the formation of indene compounds via a tandem [3,3] sigmatropic rearrangement/intramolecular hydroarylation process, whereas simply adding water to the reaction mixture produced enone derivatives cleanly. Several mechanistic hypotheses, including the hydrolysis of an allenol ester intermediate and SN2' addition of water, were examined to gain an insight into this transformation. Mechanistic investigations and computational studies support [(NHC)AuOH], produced in situ from [(NHC)AuSbF6] and H2O, instead of cationic [(NHC)AuSbF6] as the catalytically active species. Based on DFT calculations performed at the B3LYP level of theory, a full catalytic cycle featuring an unprecedented transfer of the OH moiety bound to the gold center to the C[triple chemical bond]C bond leading to the formation of a gold-allenolate is proposed. 相似文献