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Nicky J. Willis Dr. Christopher D. Bray 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9160-9173
ortho‐Quinone methides (o‐QMs) are emerging as highly useful intermediates, the inherent reactivity of which can be used in linchpin reactions for the construction of complex natural products. This review encompasses the major contributions in this field, exemplifying the major strategies and reactivity modes which can be applied. 相似文献
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Catalytic Asymmetric Cycloaddition of In Situ‐Generated ortho‐Quinone Methides and Azlactones by a Triple Brønsted Acid Activation Strategy 下载免费PDF全文
Xiao‐Ye Yu Prof. Dr. Jia‐Rong Chen Qiang Wei Hong‐Gang Cheng Zhi‐Cheng Liu Prof. Dr. Wen‐Jing Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6774-6778
A convergent and highly stereoselective [4+2] cycloaddition of in situ‐generated ortho‐Quinone methides (o‐QMs) and azlactone enols has been successfully developed through a triple Brønsted acid catalysis strategy. This protocol provides an efficient and mild access to various densely functionalized dihydrocoumarins bearing adjacent quaternary and tertiary stereogenic centers in high yields with excellent diastereo‐ and enantioselectivity. 相似文献
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Enantio‐ and Diastereoselective Access to Distant Stereocenters Embedded within Tetrahydroxanthenes: Utilizing ortho‐Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalysis 下载免费PDF全文
M. Sc. Chien‐Chi Hsiao M. Sc. Hsuan‐Hung Liao Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2014,53(48):13258-13263
A protocol for the highly enantioselective synthesis of 9‐substituted tetrahydroxanthenones by means of asymmetric Brønsted acid catalysis has been developed. A chiral binol‐based N‐triflyphosphoramide was found to promote the in situ generation of ortho‐quinone methides and their subsequent reaction with 1,3‐cyclohexanedione to provide the desired products with excellent enantioselectivities. In addition, a highly enantio‐ and diastereoselective Brønsted acid catalyzed desymmetrization of 5‐monosubstituted 1,3‐dicarbonyl substrates with ortho‐quinone methides gives rise to valuable tetrahydroxanthenes containing two distant stereocenters. 相似文献
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Brønsted Acid Catalyzed Asymmetric Hydroamination of Alkenes: Synthesis of Pyrrolidines Bearing a Tetrasubstituted Carbon Stereocenter 下载免费PDF全文
Dr. Jin‐Shun Lin Peng Yu Lin Huang Pan Zhang Prof. Dr. Bin Tan Prof. Dr. Xin‐Yuan Liu 《Angewandte Chemie (International ed. in English)》2015,54(27):7847-7851
The first highly enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes enables the efficient construction of a series of chiral (spirocyclic) pyrrolidines with an α‐tetrasubstituted carbon stereocenter with excellent functional group tolerance. A unique feature of this strategy is the use of a thiourea group acting as both the activating and the directing group through cooperative multiple hydrogen bonding with a Brønsted acid and the double bond. The utility of this method is highlighted by the facile construction of chiral synthetic intermediates and important structural motifs that are widely found in organic synthesis. 相似文献
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Phosphoric Acid Catalyzed Asymmetric 1,6‐Conjugate Addition of Thioacetic Acid to para‐Quinone Methides 下载免费PDF全文
Nan Dong Zhi‐Pei Zhang Dr. Xiao‐Song Xue Prof. Xin Li Prof. Jin‐Pei Cheng 《Angewandte Chemie (International ed. in English)》2016,55(4):1460-1464
An asymmetric 1,6‐conjugate addition of thioacetic acid with para‐quinone methides has been developed by using chiral phosphoric acid catalysis in the presence of water. A series of sulfur‐containing compounds were thus obtained in high yields with good to excellent enantioselectivities. Theoretical studies indicated that the water‐bridged proton transfer is a potentially favorable reaction pathway. An unprecedented O?H???π interaction between water and the aromatic nucleus of chiral phosphoric acid was discovered to contribute significantly to the stereocontrol in the catalysis. 相似文献
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Brønsted Acid Catalyzed Addition of Enamides to ortho‐Quinone Methide Imines—An Efficient and Highly Enantioselective Synthesis of Chiral Tetrahydroacridines 下载免费PDF全文
M. Sc. Martin Kretzschmar M. Sc. Tomáš Hodík Prof. Dr. Christoph Schneider 《Angewandte Chemie (International ed. in English)》2016,55(33):9788-9792
The direct and highly enantioselective synthesis of tetrahydroacridines was achieved through the phosphoric acid catalyzed addition of enamides to in situ generated ortho‐quinone methide imines and subsequent elimination. This novel one‐step process constitutes a very efficient, elegant, and selective synthetic approach to valuable N‐heterocycles with a 1,4‐dihydroquinoline motif. By subsequent highly diastereoselective hydrogenation and N‐deprotection the reaction products were easily converted into free hexahydroacridines with a total of three new stereogenic centers. 相似文献
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Brønsted Acid‐Catalyzed Three‐Component 1,3‐Dipolar Cycloadditions of 1,2‐Disubstituted Alkynes with Aldehyde‐Generated Azomethine Ylides 下载免费PDF全文
Wei Tan Bai‐Xiang Du Lu Guo Mei Li Gui‐Juan Xing Feng Shi 《Journal of heterocyclic chemistry》2015,52(4):1055-1061
The first 1,3‐dipolar cycloadditions (1,3‐DCs) of 1,2‐disubstituted alkynes with aldehyde‐generated azomethine ylides have been established, leading to the efficient synthesis of poly‐substituted 2,5‐dihydropyrroles.The Brønsted acid‐catalyzed three‐component 1,3‐DCs of but‐2‐ynedioates, aldehydes, and diethyl 2‐aminomalonate tolerate a wide range of substrates, offering structurally diverse poly‐substituted 2,5‐dihydropyrroles in high yields. This protocol not only provides an easy and efficient approach to poly‐substituted 2,5‐dihydropyrroles but also greatly enriches the chemistry of 1,3‐DCs, especially alkyne‐involved 1,3‐DCs. 相似文献
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Perfluoroalkylation of Unactivated Alkenes with Acid Anhydrides as the Perfluoroalkyl Source 下载免费PDF全文
Dr. Shintaro Kawamura Prof. Dr. Mikiko Sodeoka 《Angewandte Chemie (International ed. in English)》2016,55(30):8740-8743
An efficient perfluoroalkylation of unactivated alkenes with perfluoro acid anhydrides was developed. Copper salts play a crucial role as a catalyst to achieve allylic perfluoroalkylation with the in situ generated bis(perfluoroacyl) peroxides. Furthermore, carboperfluoroalkylation of alkene bearing an aromatic ring at an appropriate position on the carbon side chain was found to proceed under metal‐free conditions to afford carbocycles or heterocycles bearing a perfluoroalkyl group. This method, which makes use of readily available perfluoroalkyl sources, offers a convenient and powerful tool for introducing a perfluoroalkyl group onto an sp3 carbon to construct synthetically useful skeletons. 相似文献
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Biming Mao Honglei Liu Zhengyang Yan Yi Xu Jiaqing Xu Wei Wang Yongjun Wu Hongchao Guo 《Angewandte Chemie (International ed. in English)》2020,59(28):11316-11320
A palladium‐catalyzed asymmetric [4+2] cycloaddition of 2‐methylidenetrimethylene carbonate with alkenes derived from pyrazolones, indandione, or barbiturate has been successfully developed, affording pharmacologically interesting chiral tetrahydropyran‐fused spirocyclic scaffolds. The target compounds were generated in good to excellent yields and with high enantioselectivity (up to 99 % ee). Furthermore, this cycloaddition reaction could be efficiently scaled up, and several synthetic transformations were accomplished for the construction of other useful chiral spiropyrazolone and spiroindandione derivatives. 相似文献
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Vibeke H. Lauridsen Lise Ibsen Jakob Blom Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3259-3263
Conjugated cyclic trienes have the potential for different types of cycloaddition reactions. In the present work, we will, in a novel asymmetric cycloaddition reaction, demonstrate that the organocatalytic reaction of 2‐acyl cycloheptatrienes with azomethine ylides proceeds as a [3+2] cycloaddition, which is in contrast to the Lewis acid‐catalyzed reaction, in which a [3+6] cycloaddition takes place. In the presence of a chiral organosuperbase, 2‐acyl cycloheptatrienes react in a highly enantioselective manner in the [3+2] cycloaddition with azomethine ylides, providing the 1,3‐dipolar cycloaddition product in high yields and up to 99 % ee. It is also shown that the diene formed by the reaction can undergo stereoselective dihydroxylation, bromination, and cycloaddition reactions. Finally, based on experimental observations, some mechanistic considerations are discussed. 相似文献
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Kinetic Resolution of Azomethine Imines by Brønsted Acid Catalyzed Enantioselective Reduction 下载免费PDF全文
Amanda Bongers Patrick J. Moon Prof. Dr. André M. Beauchemin 《Angewandte Chemie (International ed. in English)》2015,54(51):15516-15519
Azomethine imines are valuable substrates in asymmetric catalysis, and can be precursors to β‐amino carbonyl compounds and complex hydrazines. However, their utility is limited because complex and enantioenriched azomethine imines are often unavailable. Reported herein is a kinetic resolution of N,N′‐cyclic azomethine imines by enantioselective reduction (s=13–43). This resolution was accomplished using a Brønsted acid catalyst, and represents the first example of the asymmetric reduction of azomethine imines. The pyrazolidinone product (up to 86 % ee) and the recovered azomethine imine (up to 99 % ee) can both be used to access the opposite enantiomers of valuable products. 相似文献