共查询到20条相似文献,搜索用时 15 毫秒
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Xiaoming Ma Xiaofeng Zhang Guoshu Xie John Mark Awad Wei Zhang 《Tetrahedron letters》2019,60(40):151127
The one-pot synthesis of tetrahydro-epiminobenzo[b]azocines through a sequential 1,3-dipolar cycloaddition and intramolecular Staudinger-aza-Wittig reaction sequence is reported. This methodology provides a new and efficient approach for medium-sized and bridged nitrogen heterocyclic molecules. 相似文献
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《Tetrahedron》2019,75(40):130571
An efficient asymmetric [3 + 2]-cycloaddition reaction of 3-isothiocyanato oxindoles and formaldimines in-situ generated from 1,3,5-trisubstituted-hexahydro-1,3,5-triazines with a cinchona alkaloid-derived thiourea as the catalyst has been developed. A range of biologically important spiro-imidazolidinethione-oxindoles were obtained in excellent yields with good enantioselectivities (up to 99% yield and 93% ee). 相似文献
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The s mall heterocyclic ring of the 1,2,3‐triazole module is one of the most widely investigated compounds in numerous applications of biological, medicinal, pharmaceutical and materially important molecules. In this regard, a large number of synthetic methodologies and approaches have already been reported to construct such a heterocyclic core structure in a selective manner. However, the vinyl‐substituted 1,2,3‐triazole moiety is another privileged segment in heterocyclic chemistry. The selective introduction of simple vinyl and functionalized vinyl groups onto the three different positions of the 1,2,3‐triazole framework can significantly improve the properties of the molecule. Accordingly, high‐yielding efficient approaches for the selective construction of vinyl‐containing 1,2,3‐triazoles becomes a promising branch of chemistry among practitioners of industry and academia. In this minireview, we have discussed recent advances in the construction of highly selective three different vinyl‐containing 1,2,3‐triazoles. In addition, representative synthetic methodologies and approaches for the corresponding three different classes of vinyl‐1,2,3‐triazoles and their applications have been described as well in this review. 相似文献
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O. V. Korenchenko A. Yu. Aksinenko V. B. Sokolov A. N. Pushin I. V. Martynov 《Russian Chemical Bulletin》1995,44(9):1740-1744
The [2+4]-cycloadditions of alkoxycarbonylimines of hexafluoroacetone to cyclopentadiene andN-nitriles have been studied. Alkoxycarbonylimines of hexafluoroacetone may be considered as both dienophiles and 1,3-heterodienes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1809–1813, September, 1995. 相似文献
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Dr. Swamy Peraka Mohammed Anif Pasha Dr. Guguloth Thirupathi Prof. Dr. Dhevalapally B. Ramachary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14036-14041
Lawsones were transformed into the functionally rich framework of methanodibenzo[a,f]azulenes and methanobenzo[f]azulenes in a single- or two-pot operation through five organocatalytic sequential reactions in very good yields with excellent selectivities. These resultant molecules are basic skeletons of important antibiotics, which highlights the value of this formal intramolecular [3+2]-cycloaddition as a key protocol. 相似文献
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Catalyst-Free [3+2] Cycloaddition of Isoquinolinium/Pyridinium Ylides and Electron-Deficient Alkenes
Xueting Zhou Jun Shi Jun-Rong Song Prof. Dr. Wei-Dong Pan Prof. Dr. Hai Ren Prof. Dr. Wei Wu 《European journal of organic chemistry》2023,26(37):e202300563
The development of simple-to-operate methods for the preparation of indolizidine derivatives are of great importance. A mild one-pot protocol for the [3+2] cycloaddition of isoquinolinium/pyridinium ylides and electron-deficient alkenes using NaBH3CN as reductant has been developed. The protocol has a broad substrate scope (more than 40 examples) and provides various novel hexahydroindolizidine derivatives in high yields and excellent diastereoselectivities (up to >20/1). 相似文献
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Twelve kinds of ketene [2+2] cycloadditions have been investigated by ab initio calculations. They are composed of four ketenes
(Y–HC=C=O, Y=H, NH2, Cl, and CN) and three isoelectronic ketenophiles (ethylene, methylenimine, and formaldehyde). All the transition state geometries
obtained here are not different significantly, but the extent of formation of two covalent bonds differs appreciably. The
difference is attributable to the degree of the charge transfer interactions. One is the interaction from the π orbital and/or the lone pair orbital of a ketenophile to the LUMO of a ketene (dominant charge transfer, CT1). The other
is that from the HOMO of the ketene to the π* orbital of the ketenophile (second dominant charge transfer, ct1). CT1 contributes to the formation of only one covalent
bond, and ct1 does to the formation of the other. This independent function is characteristic of ketene [2+2] cycloadditions.
They are not concerned with the orbital phase. We also have examined Fukui's postulate that the deformation of particular
frontier orbitals causes the reaction progress. The role has been verified both by configuration analyses along the intrinsic
reaction coordinate of the ketene-ethylene reaction and by the examination of distortions of frontier-orbital shapes along
the low-frequency vibrational modes.
Received: 25 June 1998 / Accepted: 28 August 1998 / Published online: 11 November 1998 相似文献
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Fernanda M. Ribeiro Laia 《Tetrahedron letters》2009,50(45):6180-2356
The reactivity of buta-2,3-dienoates toward aziridines is reported. Allenoates react as 2π-component in the [3+2] cycloaddition with the azomethine ylide generated from cis-1-benzyl-2-benzoyl-3-phenylaziridine affording 4-methylenepyrrolidines in a site-, regio-, and stereoselective fashion. Under conventional thermolysis, cis- and trans-2-benzoyl-1-cyclohexyl-3-phenylaziridines showed a different reactivity. These aziridines participate in formal [3+2] cycloadditions with allenes via C-N bond cleavage of the three-membered ring leading to functionalized pyrroles. 相似文献
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You-Quan Zou Shu-Wen Duan Xiang-Gao Meng Xiao-Qiang Hu Shuang Gao Jia-Rong Chen Wen-Jing Xiao 《Tetrahedron》2012,68(34):6914-6919
A highly diastereoselective and regioselective [2+2]-cycloaddition reaction of 3-ylideneoxindoles has been accomplished using visible light photocatalysis. This visible light photocatalytic protocol allows an expedient access to diversely functionalized and structurally constrained oxindole derivatives containing two spirocycles and four stereogenic centers, including two all-carbon quaternary centers. 相似文献
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A selective ring-opening [3+2] cyclization reaction of benzo[d]isoxazoles with 2-bromo-propanamides has been developed.The azaoxyallyl cation intermediates are employed as C^O 3-atom synthon to build oxa-heterocycles via the selectivity of suitable cyclization partners.This transformation provides rapid access to highly functionalized 2-hydroxyaryl-oxazolines under mild conditions and excellent regioselectivity. 相似文献
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Dr. A. Suresh Kumar Dr. Guguloth Thirupathi G. Surendra Reddy Prof. Dr. Dhevalapally B. Ramachary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1177-1183
An ideal stereoselective insertion of in situ generated benzynes into lawsones through domino formal [2+2]-cycloaddition followed by rearrangement is disclosed. The reaction allowed for the preparation of biologically important benzannulated bicyclo[3.3.0]octanes in good yields and with excellent selectivities by using simple substrates and conditions. 相似文献
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Andrey B. Koldobskii Ekaterina V. Solodova Ivan A. Godovikov Valery N. Kalinin 《Tetrahedron》2008,64(40):9555-9560
The highly activated acetylenes, ethyl 4-chloro-2-oxobut-3-ynoate and ethyl 4-bromo-2-oxobut-3-ynoate, were prepared from readily available bis(trimethylstannyl)acetylene in two steps with high overall yield. An unusual ability of the former to furnish [2+2]-cycloadducts with 1,1-disubstituted alkenes in the absence of irradiation and catalysts was discovered. The cycloaddition of ethyl 4-chloro-2-oxobut-3-ynoate to the 1,2-disubstituted alkenes was shown to be effectively catalyzed with stannic chloride. 相似文献
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Generally, synthesis of hydantoin derivatives involve use of carbonyl compounds which in turn require multistep synthesis. Here, we report a new approach to assemble spirohydantoins via [2+2+2] cyclotrimerization reaction using commercially available, inexpensive hydantoin as a starting material. 相似文献
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B.A.Bhanu Prasad 《Tetrahedron letters》2004,45(6):1137-1141
An efficient synthesis of 2,4-disubstituted 1H-imidazolines from aziridines and nitriles in the presence of BF3-Et2O or triethyloxonium tetrafluoroborate has been described. The reaction proceeds via a [3+2]-cycloaddition reaction. Most of the nitriles successfully underwent cycloaddition reactions with aziridines even at room temperature in a very short time. 相似文献
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A Pd-catalyzed asymmetric decarboxylative [4+2] cycloaddition of 3-nitroindoles and vinyl benzoxazinanones is developed through a dearomatization approach. The reaction provides an efficient protocol for constructing a series of chiral tetrahydro-5H-indolo[2,3-b]quinolines in high yields and with excellent diastereo- and enantioselectivities. 相似文献
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A. B. Koldobskii E. V. Solodova I. A. Godovikov V. N. Kalinin 《Russian Chemical Bulletin》2008,57(7):1568-1570
Ethyl 4-chloro-2-oxobut-3-ynoate has been synthesized for the first time and its addition to alkyl vinyl ethers of various
structures has been studied.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1537–1539, July, 2008. 相似文献
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In contrast with the reported phosphine‐ and DABCO‐catalyzed [3+2] and [2+2] annulation of allenoates with trifluoromethylketone, the [2+2+2] annulation of allenoates and two molecules of trifluoromethylketone was found under the condition of N‐heterocyclic carbene catalysis. 相似文献