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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
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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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N‐Heterocyclic Carbene Catalyzed Cyclocondensation of α,β‐Unsaturated Carboxylic Acids: Enantioselective Synthesis of Pyrrolidinone and Dihydropyridinone Derivatives 下载免费PDF全文
Xiang‐Yu Chen Zhong‐Hua Gao Chun‐Yu Song Chun‐Lin Zhang Prof. Dr. Zhi‐Xiang Wang Prof. Dr. Song Ye 《Angewandte Chemie (International ed. in English)》2014,53(43):11611-11615
The catalytic cyclocondensation of in situ activated α,β‐unsaturated carboxylic acids was developed. N‐heterocyclic carbenes efficiently catalyzed the generation of α,β‐unsaturated acyl azolium intermediates from α,β‐unsaturated carboxylic acids via in situ generated mixed anhydrides for the enantioselective [3+2] and [3+3] cyclocondensation with α‐amino ketones and alkyl(aryl)imines, respectively. The corresponding pyrrolidinones and dihydropyridinones were isolated in good yields with high to excellent enantioselectivities. 相似文献
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Organocatalytic Enantioselective Cross‐Vinylogous Rauhut–Currier Reaction of Methyl Coumalate with Enals 下载免费PDF全文
Qiwen Liu Prof. Dr. Liansuo Zu 《Angewandte Chemie (International ed. in English)》2018,57(30):9505-9509
The organocatalytic enantioselective intermolecular cross‐vinylogous Rauhut–Currier (RC) reaction of methyl coumalate with α,β‐unsaturated aldehydes is reported, and the enals are activated by iminium catalysis to serve as the Michael acceptors and methyl coumalate is used as an activated diene to generate a latent enolate. The excellent selectivity is driven by the aromaticity of methyl coumalate, and the post transformation of this heterocyclic structure into other electron‐deficient arenes and heterocycles have addressed, in part, the challenging selectivity issues of the intermolecular cross‐RC reactions and the limited scope of iminium catalysis. 相似文献
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Phosphine‐Catalyzed Asymmetric Umpolung Addition of Trifluoromethyl Ketimines to Morita–Baylis–Hillman Carbonates 下载免费PDF全文
Peng Chen Zhenting Yue Junyou Zhang Xi Lv Lei Wang Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2016,55(42):13316-13320
A novel phosphine‐catalyzed, highly enantioselective umpolung addition of trifluoromethyl ketimines to Morita–Baylis–Hillman carbonates was developed and it provides facile access to optically active trifluoromethyl amines with a chiral tertiary stereocenter under mild reaction conditions. The salient features of this reaction include general substrate scope, mild reaction conditions, good yields, high enantioselectivity, ease of scale‐up to gram scale, and further transformations of the products. 相似文献
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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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Highly Diastereo‐ and Enantioselective Palladium‐Catalyzed [3+2] Cycloaddition of Vinyl Aziridines and α,β‐Unsaturated Ketones 下载免费PDF全文
Chao‐Fan Xu Bao‐Hui Zheng Jia‐Jia Suo Dr. Chang‐Hua Ding Prof. Dr. Xue‐Long Hou 《Angewandte Chemie (International ed. in English)》2015,54(5):1604-1607
A palladium‐catalyzed asymmetric [3+2] cycloaddition reaction of vinylaziridines with α,β‐unsaturated ketones, wherein the alkenes have a single activator, is realized in high diastereo‐ and enantioselectivity, thus affording 3,4‐disubstituted pyrrolidines in high yields with excellent ee values. The introduction of a methyl group at C1 of the vinyl group the vinylaziridines greatly improves the stereochemistry of the reaction. A plausible transition state is proposed. 相似文献