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The Divergent Synthesis of Nitrogen Heterocycles by Rhodium(II)‐Catalyzed Cycloadditions of 1‐Sulfonyl 1,2,3‐Triazoles with 1,3‐Dienes 下载免费PDF全文
Dr. Hai Shang Yuanhao Wang Dr. Yu Tian Juan Feng Prof. Dr. Yefeng Tang 《Angewandte Chemie (International ed. in English)》2014,53(22):5662-5666
The first rhodium(II)‐catalyzed aza‐[4+3] cycloadditions of 1‐sulfonyl 1,2,3‐triazoles with 1,3‐dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5‐dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza‐[3+2] cycloadditions, thus leading to 2,3‐dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza‐heterocycles from common rhodium(II) iminocarbene intermediates. 相似文献
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Dr. Rong Zhou Kai Zhang Ling Han Yusong Chen Prof. Dr. Ruifeng Li Prof. Dr. Zhengjie He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5883-5887
An unusual formal [1+4] annulation of α‐dicarbonyl compounds with 1,1‐dicyano‐1,3‐dienes has been realized, leading to facile syntheses of cyclopentenimines and cyclopentenones in a unique manner. Mechanistic investigation implies that this reaction takes place through a P(NMe2)3‐mediated cyclopropanation followed by a base‐catalyzed cyclopropane rearrangement. It therefore represents an unprecedented [1+4] annulation mode involving Kukhtin–Ramirez adducts. 相似文献
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Stefan A. Künzi Dr. Juan Manuel Sarria Toro Dr. Tim den Hartog Prof. Dr. Peter Chen 《Angewandte Chemie (International ed. in English)》2015,54(36):10670-10674
Nickel was identified as a catalyst for the cyclopropanation of unactivated olefins by using in situ generated lithiomethyl trimethylammonium triflate as a methylene donor. A mechanistic hypothesis is proposed in which the generation of a reactive nickel carbene explains several interesting observations. Additionally, our findings shed light on a report by Franzen and Wittig published in 1960 that had been retracted later owing to irreproducibility, and provide a rational basis for the systematic development of the reaction for preparative purposes as an alternative to diazomethane or Simmons–Smith conditions. 相似文献
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Expedient Synthesis of Fused Azepine Derivatives Using a Sequential Rhodium(II)‐Catalyzed Cyclopropanation/1‐Aza‐Cope Rearrangement of Dienyltriazoles 下载免费PDF全文
Erica E. Schultz Vincent N. G. Lindsay Prof. Richmond Sarpong 《Angewandte Chemie (International ed. in English)》2014,53(37):9904-9908
A general method for the formation of fused dihydroazepine derivatives from 1‐sulfonyl‐1,2,3‐triazoles bearing a tethered diene is reported. The process involves an intramolecular cyclopropanation of an α‐imino rhodium(II) carbenoid, leading to a transient 1‐imino‐2‐vinylcyclopropane intermediate which rapidly undergoes a 1‐aza‐Cope rearrangement to generate fused dihydroazepine derivatives in moderate to excellent yields. The reaction proceeds with similar efficiency on gram scale. The use of catalyst‐free conditions leads to the formation of a novel [4.4.0] bicyclic heterocycle. 相似文献
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Gold(I)‐Catalyzed Desymmetrization of 1,4‐Dienes by an Enantioselective Tandem Alkoxylation/Claisen Rearrangement 下载免费PDF全文
Hongmiao Wu Dr. Weiwei Zi Prof. Dr. Guigen Li Prof. Dr. Hongjian Lu Prof. Dr. F. Dean Toste 《Angewandte Chemie (International ed. in English)》2015,54(29):8529-8532
An enantioselective alkoxylation/Claisen rearrangement reaction was achieved by a strategic desymmetrization of 1,4‐dienes under the catalysis of (S)‐DTBM‐Segphos(AuCl)2/AgBF4. This reaction system was highly selective for the formation of 3,3‐rearrangement products, providing cycloheptenes with various substitutions in good yield and good to excellent enantioselectivity. This transformation was further extended to bicyclic ring substrates, providing the opportunity to easily assemble 5,6‐ and 6,7‐fused ring systems. 相似文献
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Reversal of the Regiochemistry in the Rhodium‐Catalyzed [4+3] Cycloaddition between Vinyldiazoacetates and Dienes 下载免费PDF全文
Dr. Pablo E. Guzmán Dr. Yajing Lian Prof. Dr. Huw M. L. Davies 《Angewandte Chemie (International ed. in English)》2014,53(48):13083-13087
A regio‐, diastereo‐, and enantioselective [4+3] cycloaddition between vinylcarbenes and dienes has been achieved using the dirhodium tetracarboxylate catalyst [Rh2(S‐BTPCP)4]. This methodology provides facile access to 1,4‐cycloheptadienes that are regioisomers of those formed from the tandem cyclopropanation/Cope rearrangement reaction of vinylcarbenes with dienes. 相似文献
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Fabio P. Cal Alois Fürstner 《Angewandte Chemie (International ed. in English)》2020,59(33):13900-13907
The heteroleptic dirhodium paddlewheel catalyst 7 with a chiral carboxylate/acetamidate ligand sphere is uniquely effective in asymmetric [2+1] cycloadditions with α‐diazo‐α‐trimethylstannyl (silyl, germyl) acetate. Originally discovered as a trace impurity in a sample of the homoleptic parent complex [Rh2((R)‐TPCP)4] ( 5 ), it is shown that the protic acetamidate ligand is quintessential for rendering 7 highly enantioselective. The ‐NH group is thought to lock the ensuing metal carbene in place via interligand hydrogen bonding. The resulting stannylated cyclopropanes undergo “stereoretentive” cross coupling, which shows for the first time that even chiral quarternary carbon centers can be made by the Stille–Migita reaction. 相似文献
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Rhodium‐Catalyzed Regioselective N2‐Alkylation of Benzotriazoles with Diazo Compounds/Enynones via a Nonclassical Pathway 下载免费PDF全文
Kai Wang Ping Chen Danqing Ji Prof. Dr. Xinhao Zhang Guangyang Xu Prof. Dr. Jiangtao Sun 《Angewandte Chemie (International ed. in English)》2018,57(38):12489-12493
A novel rhodium‐catalyzed highly selective N2‐alkylation of benzotriazoles with diazo compounds/enynones is achieved, providing N2‐alkylated benzotriazoles in good to excellent yields and with excellent N2 selectivities. Importantly, different to traditional carbene insertion into X?H (X=N, O etc) bonds, DFT calculations disclose that this selective N2‐alkylation probably proceeds through a formal 1,3‐ rather than 1,2‐H shift to give the final products. 相似文献
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Rhodium‐Catalyzed Synthesis of 4‐Bromo‐1,2‐dihydroisoquinolines: Access to Bromonium Ylides by the Intramolecular Reaction of a Benzyl Bromide and an α‐Imino Carbene 下载免费PDF全文
Jun He Yinping Shi Wanli Cheng Zengming Man Dongdong Yang Prof. Dr. Chuan‐Ying Li 《Angewandte Chemie (International ed. in English)》2016,55(14):4557-4561
Highly functionalized 4‐bromo‐1,2‐dihydroisoquinolines were synthesized from readily available 4‐(2‐(bromomethyl)phenyl)‐1‐sulfonyl‐1,2,3‐triazoles. A bromonium ylide is proposed as the key intermediate, which can be formed by the intramolecular nucleophilic attack of the benzyl bromide on the α‐imino rhodium carbene formed in the presence of the rhodium catalyst. 相似文献
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Bowen Zhang Huw M. L. Davies 《Angewandte Chemie (International ed. in English)》2020,59(12):4937-4941
The reaction of 2‐siloxycyclo‐1,3‐dienes with E‐vinyldiazoacetates in the presence of the bulky chiral dirhodium tetracarboxylate catalyst, Rh2(R‐p‐PhTPCP)4 results in an enantioselective [4+2] cycloaddition, in which three new stereogenic centers are formed. The [4+2] cycloadducts are generated as single diastereomers with high enantiocontrol (95–98 % ee). When the diene contains an additional stereogenic center, effective kinetic resolution can be achieved. 相似文献
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Rhodium(II)‐Catalyzed Intramolecular Cycloisomerizations of Methylenecyclopropanes with N‐Sulfonyl 1,2,3‐Triazoles 下载免费PDF全文
Kai Chen Zi‐Zhong Zhu Yong‐Sheng Zhang Dr. Xiang‐Ying Tang Prof. Min Shi 《Angewandte Chemie (International ed. in English)》2014,53(26):6645-6649
A novel rhodium(II)‐catalyzed tandem cycloisomerization of methylenecyclopropanes (MCPs) with N‐sulfonyl 1,2,3‐triazoles is disclosed. The reaction produces a series of highly functionalized polycyclic N heterocycles via a rhodium imino carbene intermediate. A distinct feature of this divergent synthesis is that different types of substrates control the reaction pathways. Moreover, several interesting transformations of these products to construct diazabicyclo[3.2.1]octane derivatives are also reported. 相似文献
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Concise Stereoselective Synthesis of Oxaspirocycles with 1‐Tosyl‐1,2,3‐triazoles: Application to the Total Syntheses of (±)‐Tuberostemospiroline and (±)‐Stemona‐lactam R 下载免费PDF全文
Junkai Fu Hongjuan Shen Yuanyuan Chang Prof. Dr. Chuangchuang Li Dr. Jianxian Gong Prof. Dr. Zhen Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12881-12888
A 4‐substituted‐1‐tosyl‐1,2,3‐triazole‐based stereoselective synthesis of structurally diverse oxaspirocycles is reported. The synthesis involves Rh‐catalyzed loss of nitrogen from 4‐substituted‐1‐tosyl‐1,2,3‐triazoles, Grignard reaction, and a ring‐closing metathesis reaction as key steps. By employing readily available and stable 4‐substituted‐1‐tosyl‐1,2,3‐triazoles as surrogates of diazo compounds and nitrogen sources, two types of oxaspirocycles were obtained. The latter compounds, which contain adjacent nitrogen stereocenters, could serve as the core structures of many natural products. This chemistry has been successfully applied to the total syntheses of (±)‐tuberostemospiroline and (±)‐stemona‐lactam R. 相似文献
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Dr. Sen Wai Kwok Dr. Li Zhang Dr. Neil P. Grimster Prof. Dr. Valery V. Fokin 《Angewandte Chemie (International ed. in English)》2014,53(13):3452-3456
A convenient one‐pot asymmetric synthesis of 2,3‐dihydropyrroles from in situ generated triflated triazoles and olefins is described that further expands the utility of azavinyl carbene chemistry and provides access to an important class of cyclic enamides. Mechanistic investigations support the involvement of triflated cyclopropylaldimine intermediates in the formation of 2,3‐dihydropyrrole. To the best of our knowledge, this is the first example of a chiral Brønsted acid catalyzed rearrangement of cyclopropylimines into enantioenriched 2,3‐dihydropyrroles. 相似文献