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1.
Organocatalytic Cascade Reactions: Towards the Diversification of Hydroisochromenes and Chromenes through Two Different Activation Modes 下载免费PDF全文
Dr. David Cruz Cruz Rasmus Mose Dr. Clarisa Villegas Gómez Stine V. Torbensen Martin S. Larsen Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11331-11335
The organocatalytic enantioselective syntheses of functionalized hydroisochromenes and chromenes by trienamine‐mediated [4+2]‐cycloaddition/nucleophilic ring‐closing and iminium‐ion/aminal‐mediated oxa‐Michael/Michael/nucleophilic ring‐closing with 2‐nitroallylic alcohols are presented. The corresponding cycloadducts, with up to five stereocenters, are formed in good yield and excellent enantioselectivities. The synthetic applications of the obtained products have been demonstrated. 相似文献
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Yan Zhang Jia-Hui Yang Ying-Qi Xia Lin Dong Fen-Er Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6183-6186
An efficient asymmetric Mannich/cyclization cascade strategy was established from 2-benzothiazolimines with N-acylpyrazoles to provide optical active benzothiazolopyrimidine derivatives using a copper-based complex. The mild cascade process constructed various structurally diverse products with broad scope of substrates together with excellent enantioselectivities (up to 99 % ee) and diastereoselectivities (up to 99:1 d.r.). 相似文献
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《化学:亚洲杂志》2017,12(24):3119-3122
A palladium‐catalyzed asymmetric redox‐relay Heck reaction of 4H ‐chromenes and arylboronic acids has been successfully developed. The reaction proceeded in moderate to good yields with good to high enantioselectivities. The resulting product is an advanced intermediate of bio‐active compound BW683C. 相似文献
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Abhijeet Singh Jagmeet Singh Prof. Dr. Mahendra Nath 《European journal of organic chemistry》2023,26(4):e202201319
A facile synthetic strategy for the synthesis of a new series of β,β’-fused 2-arylpyrimido[4,5-b]porphyrins has been developed by using condensation cyclization reaction with ammonia. 2-Aroylamino-3-formylporphyrins were synthesized from 2-aroylaminoporphyrins under Vilsmeier–Haack reaction conditions, which were then efficiently converted to the corresponding 2-arylpyrimido[4,5-b]-5,10,15,20-tetrakis(4-chlorophenyl)-porphyrins via a condensation cyclization reaction. The nickel(II), copper(II), free-base and zinc(II) analogues of 2-arylpyrimido[4,5-b]porphyrins were successfully synthesized in 65–72 % yields and structurally characterized on the basis of spectral data analysis. On photophysical evaluation, 2-arylpyrimido[4,5-b]porphyrins demonstrated a 12–19 nm bathochromic shift in their electronic absorption spectra and up to 10 nm red shift in their emission spectra as compared to the simple meso-(tetrakis(4-chlorophenyl))porphyrins due to the extended π-conjugation. 相似文献
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Dan Du Dr. Qin Xu Xiao‐Ge Li Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4733-4737
On the basis of asymmetric regioselective [3+2] or [3+2]/[4+2] cascade reaction of 3‐isothiocyanato oxindoles with C=C and C=N bonds of α,β‐unsaturated methanesulfonamides, diversified S‐containing heterocyclic spirooxindole derivatives could be obtained in high yields along with good to excellent diastereo‐ and enantioselectivities under mild conditions in the presence of cinchona alkaloid‐derived organocatalysts. 相似文献
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以2-氯-5-氯甲基吡啶(CCMP)、无水乙二胺和硝基胍为原料,运用串联反应方法合成了吡虫啉[化学名:1-(6-氯-3-吡啶甲基)-N-硝基-2-咪唑啉亚胺]。该方法反应中间体无需纯化处理,操作简单,同时解决了活性中间体进一步进行副反应的难题。通过单因素实验,探讨了pH、反应溶剂、温度以及时间等因素对产物收率的影响,得到的优化工艺条件为:以乙腈为溶剂,nCCMP∶n无水乙二胺∶n硝基胍=1∶5∶1,于30℃反应120min,产率可达96.35%。其结构经1H NMR、13C NMR、IR表征。 相似文献
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Hao Wu Li‐Li Zhang Zhi‐Qing Tian Dr. Yao‐Dong Huang Prof. Yong‐Mei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1747-1753
Bispirooxindole derivatives containing three stereocenters, including two spiro quaternary centers, were synthesized in a high‐yielding, atypically rapid, and stereocontrolled cascade Michael–cyclization reaction between methyleneindolinones and isothiocyanato oxindoles catalyzed by a bi‐ or multifunctional organocatalyst. Mild conditions were used to construct bispirooxindoles with excellent enantio‐ and diastereomeric purities within less than 1 min. Catalyst reconfiguration offered access to the opposite enantiomer. This exceptionally highly efficient procedure will allow diversity‐oriented syntheses of this intriguing class of compounds with potential biological activities. 相似文献
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Chenguang Yu He Huang Xiangmin Li Prof. Dr. Yueteng Zhang Hao Li Prof. Dr. Wei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9240-9246
In this study, we report the harnessing of new reactivity of N,O‐acetals in an aminocatalytic fashion for organic synthesis. Unlike widely used strategies requiring the use of acids and/or elevated temperatures, direct replacement of the amine component of the N,O‐acetals by carbon‐centered nucleophiles for C?C bond formation is realized under mild reaction conditions. Furthermore, without necessary preformation of the N,O‐acetals, an amine‐catalyzed in situ formation of N,O‐acetals is developed. Coupling both reactions into a one‐pot operation enables the achievement of a catalytic process. We demonstrate the employment of simple anilines as promoters for the cyclization–substitution cascade reactions of trans‐2‐hydroxycinnamaldehydes with various carbonic nucleophiles including indoles, pyrroles, naphthols, phenols, and silyl enol ethers. The process offers an alternative approach to structurally diverse, “privileged” 2‐substituted 2H‐chromenes. The synthetic power of the new process is furthermore shown by its application in a 2‐step synthesis of the natural product candenatenin E and for the facile installation of 2‐substituted 2H‐chromene moieties into biologically active indoles. 相似文献
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Chuan‐Gang Zhao Zhi‐Tao Feng Guo‐Qiang Xu Ang Gao Jing‐Wei Chen Zhu‐Yin Wang Peng‐Fei Xu 《Angewandte Chemie (International ed. in English)》2020,59(8):3058-3062
We herein report a general organocatalytic enantioselective strategy for the construction of highly strained spiro[2,3]hexane skeletons from methylenecyclopropanes and a broad selection of α,β‐unsaturated aldehydes. The reaction proceeds through a Michael addition followed by ring expansion of methylenecyclopropanes and nucleophilic attack of an enamine to realize the construction of spiro[2,3]hexanes. Key to the success of this approach are the utilization of an electron‐deficient difluoro‐substituted secondary amine catalyst and the intrinsic reactivity of methylenecyclopropanes. 相似文献
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A formal [4+2] propargylic annulation of indoles and pyrrole with ethynyl benzoxazinanones was described. This protocol provides a concise synthesis of tetrahydro‐5H‐indolo[2,3‐b]quinolines and tetrahydro‐3H‐pyrrolo[3,2‐b]quinoline, the core structures of alkaloid frameworks, featuring excellent yields, high diastereoselectivity, mild conditions and wide substrate scope. 相似文献
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A facile synthesis of benzofuro[2,3‐c]pyridines has been achieved under mild conditions by using ammonium acetate as the nitrogen source through intramolecular cascade annulation. This reaction could efficiently construct pyridine ring and furan ring in one step. Moreover, the key annulation step was demonstrated through dihydrobenzofuran intermediates. 相似文献
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《Helvetica chimica acta》2018,101(2)
Phaitanthrin E was biomimetically synthesized from methyl indole‐3‐carboxylate and methyl anthranilate or anthranilic acid using the ester group as an activating group. The reaction proceeds through NCS‐mediated dearomatization/TFA‐catalyzed protonation of indolenine/C(2) amination/Et3N‐promoted aromatization and cyclization in one‐pot procedure. This method is capable of converting simple biomass materials to phaitanthrin E. The synthesis not only allows assessment of antiproliferative activity, but also affords experimental support for the hypothetical biosynthetic pathway of phaitanthrin E. The resulting phaitanthrin E derivatives were evaluated for in vitro antiproliferative activity against human colorectal cancer cells (DLD‐1). The biogenetic intermediate of phaitanthrin E showed higher antiproliferative activity than the natural product, phaitanthrin E. Furthermore, a concise synthesis of tryptanthrin is also accomplished from indole‐3‐carbaldehyde and methyl anthranilate using the aldehyde group as an activating group. 相似文献
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Rahim Hekmatshoar Yahya S. Beheshtiha Monire Kheirkhah Farnoosh Faridbod 《Monatshefte für Chemie / Chemical Monthly》2002,133(5):669-672
Summary. Protonation of the highly reactive 1:1-intermediate produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate
by naphthols lead to vinyl triphenylphosphonium salts which undergo an aromatic electrophilic substitution reaction with the
conjugated base to produce the title compounds.
Received August 14, 2001. Accepted November 22, 2001 相似文献
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Enantioselective Cascade Michael Addition/Cyclization Reactions of 3‐Nitro‐2H‐Chromenes with 3‐Isothiocyanato Oxindoles: Efficient Synthesis of Functionalized Polycyclic Spirooxindoles 下载免费PDF全文
Fen Tan Dr. Liang‐Qiu Lu Qing‐Qing Yang Wei Guo Qiao Bian Prof. Dr. Jia‐Rong Chen Prof. Dr. Wen‐Jing Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3415-3420
An unprecedented Zn(OTf)2‐catalyzed asymmetric Michael addition/cyclization cascade of 3‐nitro‐2H‐chromenes with 3‐isothiocyanato oxindoles has been disclosed. This transformation provides an efficient access to various synthetically important polycyclic spirooxindoles in a highly stereoselective manner under mild conditions (72–99 % yields, up to >95:5 d.r. and >99 % ee). The reaction leads to the formation of three consecutive stereocenters, including 1,3‐nonadjacent tetrasubstituted carbon stereocenters, in a single operation. A bifunctional activation model of the chiral Zn(OTf)2/bis(oxazoline) complex was proposed based on control experiments, wherein the ZnII moiety serves as a Lewis acid and the N atom of the free NH group acts as a Lewis base by a hydrogen‐bonding interaction. 相似文献
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2,7-Diazabicyclo[3.3.0]octan-4-ol (1) and 2,7-diazabicyclo[3.3.0]oct-4-ene (2) are synthesized by the desulfonylation using Mg-HgCl2(cat.) of β-hydroxy sulfone derivatives which have been prepared via cyclization of sulfone ester derivative. 相似文献