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1.
We report herein the first example of asymmetric hydroazidation of α-substituted vinyl ketones by using chiral primary amines as the catalysts.A simple chiral primary-tertiary diamine catalyst derived from lphenylalanine was found to readily promote this aza-Michael addition reaction with enamine protonation as the key stereogenic step,thus enabling the effective synthesis of α-chiral β-azido ketones with good yields and moderate enantioselectivities. 相似文献
2.
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
3.
Catalytic Asymmetric Construction of 3,3′‐Spirooxindoles Fused with Seven‐Membered Rings by Enantioselective Tandem Reactions 下载免费PDF全文
Yang Wang Prof. Dr. Feng Shi Xi‐Xi Yao Meng Sun Liang Dong Prof. Shu‐Jiang Tu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15047-15052
The first catalytic asymmetric construction of a spirooxindole scaffold incorporated with a seven‐membered benzodiazepine moiety has been established by a three‐component (isatin, 1,2‐phenylenediamine, cyclohexane‐1,3‐dione) tandem reaction catalyzed by a chiral phosphoric acid. Structurally complex spirobenzodiazepine oxindoles with one quaternary stereogenic center are obtained in high yield with excellent enantioselectivity (up to 99 % yield, enantiomeric ratio>99.5:0.5). This approach takes advantage of organocatalytic asymmetric tandem reactions to efficiently construct the structurally rigid spirobenzodiazepine oxindole architecture with high enantiopurity in a single transformation, which involves a cascade enamine–imine formation/intramolecular Mannich reaction sequence. 相似文献
4.
Dong Xing Xiaotian Qi Daniel Marchant Peng Liu Guangbin Dong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4410-4414
Herein, we describe an intermolecular direct branched‐selective α‐alkylation of cyclic ketones with simple alkenes as the alkylation agents. Through an enamine‐transition metal cooperative catalysis mode, the α‐alkylation is realized in an atom‐ and step‐economic manner with excellent branched selectivity for preparing β‐branched ketones. Employment of a pair of bulky Brønsted acid and base as additives is responsible for enhanced efficiency. Promising enantioselectivity (74 % ee) has been obtained. Experimental and computational mechanistic studies suggest that a pathway through alkene migratory insertion into the Ir?C bond followed by C?H reductive elimination is involved for the high branched selectivity. 相似文献
5.
Longji Li Yao Li Niankai Fu Long Zhang Sanzhong Luo 《Angewandte Chemie (International ed. in English)》2020,59(34):14347-14351
Asymmetric catalysis with benzyne remains elusive because of the highly fleeting and nonpolar nature of benzyne intermediates. Reported herein is an electrochemical approach for the oxidative generation of benzynes (cyclohexyne) and its successful merging with chiral primary aminocatalysis, formulating the first catalytic asymmetric enamine–benzyne (cyclohexyne) coupling reaction. Cobalt acetate was identified to stabilize the in situ generated arynes and facilitate its coupling with an enamine. This catalytic enamine‐benzyne protocol provides a concise method for the construction of diverse α‐aryl (α‐cyclohexenyl) quaternary carbon stereogenic centers with good stereoselectivities. 相似文献
6.
Qing‐Xia Zhang Yao Li Jie Wang Chen Yang Cheng‐Jun Liu Xin Li Jin‐Pei Cheng 《Angewandte Chemie (International ed. in English)》2020,59(11):4550-4556
The enantioselective ketimine–ene reaction is one of the most challenging stereocontrolled reaction types in organic synthesis. In this work, catalytic enantioselective ketimine–ene reactions of 2‐aryl‐3H‐indol‐3‐ones with α‐methylstyrenes were achieved by utilizing a B(C6F5)3/chiral phosphoric acid (CPA) catalyst. These ketimine–ene reactions proceed well with low catalyst loading (B(C6F5)3/CPA=2 mol %/2 mol %) under mild conditions, providing rapid and facile access to a series of functionalized 2‐allyl‐indolin‐3‐ones with very good reactivity (up to 99 % yield) and excellent enantioselectivity (up to 99 % ee). Theoretical calculations reveal that enhancement of the acidity of the chiral phosphoric acid by B(C6F5)3 significantly reduces the activation free energy barrier. Furthermore, collective favorable hydrogen‐bonding interactions, especially the enhanced N?H???O hydrogen‐bonding interaction, differentiates the free energy of the transition states of CPA and B(C6F5)3/CPA, thereby inducing the improvement of stereoselectivity. 相似文献
7.
Origins of the Enantio‐ and N/O Selectivity in the Primary‐Amine‐Catalyzed Hydroxyamination of 1,3‐Dicarbonyl Compounds with In‐Situ‐Formed Nitrosocarbonyl Compounds: A Theoretical Study 下载免费PDF全文
Dr. Long Zhang Changming Xu Prof. Dr. Xueling Mi Prof. Dr. Sanzhong Luo 《化学:亚洲杂志》2014,9(12):3565-3571
Chemoselective control over N/O selectivity is an intriguing issue in nitroso chemistry. Recently, we reported an unprecedented asymmetric α‐amination reaction of β‐ketocarbonyl compounds that proceeded through the catalytic coupling of enamine carbonyl groups with in‐situ‐generated carbonyl nitroso moieties. This process was facilitated by a simple chiral primary and tertiary diamine that was derived from tert‐leucine. This reaction featured high chemoselectivity and excellent enantioselectivity for a broad range of substrates. Herein, a computational study was performed to elucidate the origins of the enantioselectivity and N/O regioselectivity. We found that a bidentate hydrogen‐bonding interaction between the tertiary N+? H and nitrosocarbonyl groups accounted for the high N selectivity, whilst the enantioselectivity was determined by Si‐facial attack on the (E)‐ and (Z)‐enamines in a Curtin–Hammett‐type manner. The bidentate hydrogen‐bonding interaction with the nitrosocarbonyl moieties reinforced the facial selectivity in this process. 相似文献
8.
Merging Aerobic Oxidation and Enamine Catalysis in the Asymmetric α‐Amination of β‐Ketocarbonyls Using N‐Hydroxycarbamates as Nitrogen Sources 下载免费PDF全文
Changming Xu Dr. Long Zhang Prof. Dr. Sanzhong Luo 《Angewandte Chemie (International ed. in English)》2014,53(16):4149-4153
We describe herein an unprecedented asymmetric α‐amination of β‐ketocarbonyls under aerobic conditions. The process is enabled by a simple chiral primary amine through the coupling of a catalytic enamine ester intermediate and a nitrosocarbonyl (generated in situ) derived from N‐hydroxycarbamate. The reaction features high chemoselectivity and excellent enantioselectivity for a broad range of substrates. 相似文献
9.
Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation 下载免费PDF全文
Dr. Chao Xu Calum W. Muir Dr. Andrew G. Leach Dr. Alan R. Kennedy Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2018,57(35):11374-11377
The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N‐heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular asymmetric proton transfer from the ion‐paired prochiral intermediate. 相似文献
10.
Base‐Free Conditions for Rhodium‐Catalyzed Asymmetric Arylation To Produce Stereochemically Labile α‐Aryl Ketones 下载免费PDF全文
Dr. Xiaowei Dou Prof. Dr. Yixin Lu Prof. Dr. Tamio Hayashi 《Angewandte Chemie (International ed. in English)》2016,55(23):6739-6743
The asymmetric arylation of 2,2‐dialkyl cyclopent‐4‐ene‐1,3‐diones with aryl boronic acids was found to be efficiently catalyzed by a chiral diene–rhodium μ‐chloro dimer, [{RhCl((R)‐diene*)}2], in the absence of bases in toluene/H2O to give 2,2‐dialkyl 4‐aryl cyclopentane‐1,3‐diones in high yields with high enantioselectivity. Such compounds can not be obtained with high enantiomeric purity under the standard basic conditions used for rhodium‐catalyzed asymmetric arylation because the α‐aryl ketone products undergo racemization under the basic conditions. 相似文献
11.
Density functional theory calculations are used to study the reaction mechanism and origins of high stereoselectivity in chiral guanidine‐catalyzed asymmetric 1,4‐addition of 5H‐oxazol‐4‐ones. The reaction involves proton abstraction of 5H‐oxazol‐4‐one, C—C bond formation, and proton transfer. N1 atom of chiral guanidine exchanges its character as base and acid to activate 5H‐oxazol‐4‐one and to facilitate the product formation. The role of N2—H2 is not only H‐bond donor for 5H‐oxazol‐4‐one but also electron accepter for N1. The enantioselectivity related with rate‐limiting step 1 and Z/E selectivity determined in step 2 are primarily influenced by a five to six‐membered ring link in the backbone of chiral guanidine. The reaction proceeds along the favorable path with smaller rotations of the linked bonds. The enantioselectivity is improved with guanidine involving an electron‐deficient and bulky substituent. With methyl ether‐protected hydroxy in structure, the catalytic ability and enantioselective control of guanidine are extraordinarily low, affording the opposite enantiomer as major product. Z‐isomers are preferred in all cases. © 2013 Wiley Periodicals, Inc. 相似文献
12.
Dr. Sandip Murarka Zhi‐Jun Jia Dr. Christian Merten Dr. Constantin‐G. Daniliuc Dr. Andrey P. Antonchick Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(26):7653-7656
We report a rhodium(II)‐catalyzed highly enantioselective 1,3‐dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α‐diazoketone‐derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. 相似文献
13.
Calum McLaughlin Alexandra M. Z. Slawin Andrew D. Smith 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(42):15255-15263
An isothiourea‐catalyzed enantioselective Michael addition of aryl ester pronucleophiles to vinyl bis‐sulfones via C(1)‐ammonium enolate intermediates has been developed. This operationally simple method allows the base‐free functionalization of aryl esters to form α‐functionalized products containing two contiguous tertiary stereogenic centres in excellent yield and stereoselectivity (all ≥99:1 er). Key to the success of this methodology is the multifunctional role of the aryloxide, which operates as a leaving group, Brønsted base, Brønsted acid and Lewis base within the catalytic cycle. Comprehensive mechanistic studies, including variable time normalization analysis (VTNA) and isotopologue competition experiments, have been carried out. These studies have identified (i) orders of all reactants; (ii) a turnover‐limiting Michael addition step, (iii) product inhibition, (iv) the catalyst resting state and (v) catalyst deactivation through protonation. 相似文献
14.
Arun Suneja Henning Jakob Loui Christoph Schneider 《Angewandte Chemie (International ed. in English)》2020,59(14):5536-5540
We describe herein a highly diastereo‐ and enantioselective [4+3]‐cycloannulation of ortho‐quinone methides and carbonyl ylides to furnish functionalized oxa‐bridged dibenzooxacines with excellent yields and stereoselectivity in a single synthetic step. The combination of rhodium and chiral phosphoric acid catalysis working in concert to generate both transient intermediates in situ provides direct access to complex bicyclic products with two quaternary and one tertiary stereogenic centers. The products may be further functionalized into valuable and enantiomerically highly enriched building blocks. 相似文献
15.
Rhodium‐catalyzed Asymmetric Hydrogenation of α‐Dehydroamino Ketones: A General Approach to Chiral α‐amino Ketones 下载免费PDF全文
Rhodium/DuanPhos‐catalyzed asymmetric hydrogenation of aliphatic α‐dehydroamino ketones has been achieved and afforded chiral α‐amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β‐amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α‐amino ketones and chiral β‐amino alcohols. 相似文献
16.
Chiral C3‐symmetric trialkyl phosphites, derivatives, of (−)‐(1R,2S,5R)‐menthol, and (−)‐di‐O‐isopropylidene‐1,2:5,6‐α‐D ‐glucofuranose, have been studied as starting reagents for the preparation of chiral organophosphorus compounds. The reactions involve induction at the α‐carbon atom of substituted α‐alkylphosphonates. The stereoselectivity of the reaction depends on the structure of the starting compounds and the reaction conditions. The configurations of the alkylphosphonates were defined by means of NMR spectroscopy and by transformation into corresponding alkylphosphonic acids. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:138–143, 2000 相似文献
17.
18.
Timothy B. Wright Ben W. H. Turnbull P. Andrew Evans 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9991-9995
An enantioselective rhodium‐catalyzed allylic alkylation of β,γ‐unsaturated α‐amino nitriles is described. This protocol provides a novel approach for the construction of β‐stereogenic carbonyl derivatives via the catalytic asymmetric alkylation of a homoenolate equivalent. The particularly challenging nature of this transformation is highlighted by the fact that three modes of selectivity must be manipulated, namely regio‐ and enantioselectivity, in addition to geometrical control. The γ‐stereogenic cyanoenamine products can be readily hydrolyzed in situ to afford the β‐substituted carboxylic acids, which in turn provide expedient access to a number of related carbonyl derivatives. Additionally, control experiments indicate that the chiral rhodium‐allyl intermediate facilitates the selective formation of the E‐cyanoenamine products, which is critical since the Z‐isomer affords significantly lower enantiocontrol. 相似文献
19.
Yu‐Hua Deng Jin‐Quan Chen Dr. Long He Dr. Tai‐Ran Kang Prof. Quan‐Zhong Liu Prof. Shi‐Wei Luo Prof. Wei‐Chen Yuan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7143-7150
Highly enantioselective cross‐aldol reactions between acetaldehyde and activated acyclic ketones are reported for the first time. Various acyclic ketones, such as saturated and unsaturated keto esters, reacted with acetaldehyde in the presence of a chiral primary amine and a Brønsted acid to afford optically enriched tertiary alcohols in good yields and with excellent enantioselectivities. Trifluoromethyl ketones were tolerable under the reaction conditions, thereby affording the trifluoromethyl carbinol in good‐to‐excellent yields and enantioselectivities. Structural modification of the chiral amines from the same chiral source switched the stereoselectivity of the products. The utility of aldol chemistry was demonstrated in the brief synthesis of functionally enriched δ‐lactones. Theoretical calculations on the transition‐state structure indicated that the protonated tertiary amine could effectively activate the carbonyl group of a keto ester to promote the addition process through hydrogen‐bonding interaction and, simultaneously, provide an appropriate attacking pattern for the approach of the keto ester to the enamine, which is formed from acetaldehyde and the chiral catalyst, on a particular face, resulting in high enantioselectivity. 相似文献
20.
Catalyst‐Controlled Switch in Chemo‐ and Diastereoselectivities: Annulations of Morita–Baylis–Hillman Carbonates from Isatins 下载免费PDF全文
Gu Zhan Ming‐Lin Shi Qing He Wei‐Jia Lin Dr. Qin Ouyang Dr. Wei Du Prof. Dr. Ying‐Chun Chen 《Angewandte Chemie (International ed. in English)》2016,55(6):2147-2151
Regulating both the chemo‐ and diastereoselectivity, divergently, of a reaction is highly attractive but extremely challenging. Presented herein is a catalyst‐controlled switch in the chemo‐ and diastereodivergent annulation reactions of Morita–Baylis–Hillman carbonates, derived from isatins and 2‐alkylidene‐1H‐indene‐1,3(2H)‐diones, in exclusive α‐regioselectivity. α‐Isocupreine efficiently catalyzed [2+1] reactions to access cyclopropane derivatives, and the diastereodivergent [3+2] annulations were accomplished by employing either a chiral phosphine or a DMAP‐type molecule. All reactions exhibited excellent chemoselectivities, and good to remarkable stereoselectivities were furnished, thus leading to a collection of compounds with skeletal and stereogenic diversity. Moreover, DFT computational calculations elucidated the catalyst‐based switch in mechanism. 相似文献