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Journal articles on the topic '[4+21 Cycloaddition reaction'

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Published: 5 June 2025

Last updated: 1 August 2025

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1

Mausumi, Bandyopadhyay, Datta Kalyani, and Mal Dipakranjan. "Anionic [4+2]cycloaddition-Retro[4+2]cycloaddition strategy in the synthesis of psoralen and its isoster." Journal of Indian Chemical Society Vol. 76, Nov-Dec 1999 (1999): 551–56. https://doi.org/10.5281/zenodo.5862056.

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Department of Chemistry, Indian Institute of Technology, Kharagpur-721 302, India <em>Manuscript received 27 July 1999</em> Furan-1,4-dipolar agents 7 and 16e, prepared in few steps from commercially available furoates, have been annotated with bicyclopentadienone 2 to provide pentacyclic frameworks 8 and 17 respectively. Subsequent transformations of 8 and 17 through retro-Diels-Aider reaction and indenol-indanone rearrangement have furnished psoralen precursors 14 and 19. Similarly, oxaindacenone 23 has been prepared in good yield from 21.

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2

Cameron, Donald W., and Ross M. Heisey. "Reaction of Terminally Alkyl-Substituted Oxy Dienes with Tetracyanoethylene and Other Acceptors." Australian Journal of Chemistry 53, no. 3 (2000): 161. http://dx.doi.org/10.1071/ch00035.

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The 4,4-dimethyl-substituted oxy dienes (4), (19) and (20) did not undergo cycloaddition to 1,4-quinonoid dienophiles, for steric reasons, but all reacted with tetracyanoethylene to give [4+2]- or [2+2]-adducts. Unlike the 1-oxy diene (4), the 2- and 3-oxy systems (19) and (20) did not show hydrogen-transfer chemistry towards quinones. The individual components of isomeric pairs of dienes (8), (9) and (19), (21) were differentiated by differing reactivity towards cycloaddition.

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3

Suman, Kalyan Panja, Maiti Sourav, and Bandyopadhyay Chandrakanta. "Synthesis of 8,8' -(polymethylene-/ o-xylyl-dioxy)di(pyrano[ 4,3-b ]-1-benzopyran- 10H-10-one) and its conversion to corresponding diacrolein derivative." Journal of Indian Chemical Society Vol. 88, Oct 2011 (2011): 1577–80. https://doi.org/10.5281/zenodo.5790659.

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Department of Chemistry, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata-700 118, India <em>E-mail</em> : kantachandra@rediffmail.com <em>Manuscript received 29 November 2010, accepted 21 March 2011</em> 6,6'-Tethered-di(4-oxo-4H-1-benzopyran-3-carboxaldehyde) undergoes inverse electron demand [4+ 2] cycloaddition reaction with ethoxyethene to produce endo-di(pyrano[4,3-b]-1-benzopyran), which produces diacrolein when treated with NaOMe in methanol.

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4

Regitz, Manfred, Klaus Urgast, and Gerhard Maas. "Phosphorverbindungen ungewöhnlicher Koordination, 3 [1] Vergleich des Cycloadditonsverhaltens von Diphenylketen und Triphenylphosphen / Phosphorus Compounds with Unusual Coordination, 3 [1] Comparison of the Cycloaddition Behaviour of Diphenylketene and Triphenylphosphene." Zeitschrift für Naturforschung B 40, no. 1 (1985): 67–76. http://dx.doi.org/10.1515/znb-1985-0115.

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Triphenylphosphene (3b), generated thermally or photochemically from 1b, undergoes olefination reaction with 4.5-benzotropone (6) to yield 1-(diphenylmethylen)-4.5-benzocycloheptatriene (9); the oxaphosphetane 7b is assumed to be the intermediate of this reaction. In an analogous way, 4-pyrone (15) is transformed into 4-(diphenylmethylen)pyrane (16). Corresponding olefination behaviour is observed in the reactions of 6 and 15 with diphenylketene.In the reaction of tetracyclone (20) with diphenylketene (3a), the olefination sequence leads to the formation of (diphenylmethylen)tetraphenylcyclope

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5

Seitz, Gunther, and Johanna Siegl. "Synthese neuer Pyridin-C-nukleoside der 2 ,3 -Didesoxyribose durch „inverse“ [4+2]-Cycloaddition Synthesis of Novel Pyridine-C-nucleosides of 2,3-Dideoxyribose by „Inverse“ [4+2]-Cycloaddition." Zeitschrift für Naturforschung B 52, no. 7 (1997): 851–58. http://dx.doi.org/10.1515/znb-1997-0715.

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The anomeric imido esters 5 and 6, appropriate precursors for C-nucleoside synthesis, were prepared and utilized as heterodienophiles in a Diels-Alder reaction with inverse electron demand to yield the novel, protected 1.2.4-triazine C-nucleosides 8 and 9. They could be deprotected by treatment with 70% trifluoroacetic acid to furnish the free C-nucleosides 10 and 11. The triazine „aglycon“ of 8 contains an electron deficient diazadiene system, highly activated to react with various electron rich dienophiles such as enamines, enol ethers and several cyclic ketene acetals in an „inverse“ [4+2]-

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6

Susanta, K. Borthakur, Boruah Paran, and N. Goswami Birendra. "[4+2] Cycloaddition reaction: Synthesis and antifungal activities of 2-substituted 1,2,4-triazolo[3,2-c][1,3,5]thiadiazine-3,3-dioxides." Journal of Indian Chemical Society Vol. 90, Jul 2013 (2013): 1005–8. https://doi.org/10.5281/zenodo.5774794.

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Department of Chemistry, Arya Vidyapeeth College, P.O. Gopinath Nagar, Guwahati-781 016, Assam, India <em>E-mail</em> : skbthakur@yahoo.co.in Medicinal Aromatic and Economic Plant Division, Formerly of Synthetic Organic Chemistry Division, North East Institute of Science and Technology, Jorhat-785 006, Assam, India <em>Manuscript received online 06 August 2012, revised 09 August 2012, accepted 16 August 2012</em> 3-Benzylidineamino-1,2,4-triazole undergoes [4+2] cycloaddition reaction with sulfene resulting in good yield of [1,2,4]-triazolo[3,2-<em>c</em>][1,3,5]-thiadiazine-3,3-dioxide deriva

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7

Auner, Norbert, and Claus-Rüdiger Heikenwälder. "Silaheterocyclen, XXXIII [1, 2]: Cycloadditions-Reaktionen des 1.1-Dichlor-2-neopentyIsilaethens mit Pentafulvenen / Silaheterocycles, XXXIII [1, 2]: C y clo ad d itio n Reactions of 1.1-Dichloro-2 -neopentylsilene with Pentafulvenes." Zeitschrift für Naturforschung B 52, no. 4 (1997): 500–514. http://dx.doi.org/10.1515/znb-1997-0412.

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The reaction between in situ formed 1.1-dichloro-2-neopentyl-1-silene, Cl2Si=CHCH2tBu (2), and 1,1-dimethylpentafulvene (5) leads to the formation of exo/endo-isomeric [4+2] cycloadducts 9 and [2+2] stereoisomers 10 in good yields. NMR spectroscopic investigations of the product mixture prove the different modes of the silene cycloaddition reactions ([4+2] vs [2+2] addition).Treatment of 9 and 10 with LiAlH4 and LiMe yield the stereo- and regioisomeric derivatives (LiAlH4: 16, 17: MeLi: 18. 19). whereas PhMgBr reacts with 10 to give only the mono substitution, the [4+2] compound 20. and the di

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8

Pyne, Stephen G., Javad Safaei-G., Karl Schafer, Abdollah Javidan, Brian W. Skelton, and Allan H. White. "Diastereoselective 1,3-Dipolar Cycloadditions and Michael Reactions of Azomethine Ylides to (2R)-3-Benzoyl-4-methylidene-2-phenyloxazolidin-5-one and (2S)-3-Benzoyl-2-t-butyl-4-methylideneoxazolidin-5-one." Australian Journal of Chemistry 51, no. 2 (1998): 137. http://dx.doi.org/10.1071/c97072.

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The 1,3-dipolar cycloaddition reactions of (1) and (11) with the azomethine ylides derived from N-benzylidene α-amino acid esters (2) proceed with good to high exo-diastereoselectivity giving the cycloadducts (4) and (12), respectively. The cycloaddition adducts can be converted to highly functionalised prolines (14), (15) and (17) in high enantiomeric purities. The Michael addition adducts of (1) and (11) with the azomethine ylides derived from the N-(disubstituted methylidene) α-amino acid esters (18), (19) and (33) allow for a practical synthesis of all four stereoisomers of 4-benzamidopyro

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9

Collins, DJ, TC Hughes, and WM Johnson. "Regiospecific Syntheses of the Monomethylated 3-Phenyldihydro-1,2,4-triazin-6(1H)-ones." Australian Journal of Chemistry 49, no. 4 (1996): 463. http://dx.doi.org/10.1071/ch9960463.

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Unambiguous syntheses of four unreported monomethylated derivatives of 3-phenyldihydro-1,2,4-triazin-6(1H)-ones, namely, the 1-methyl (2), 2-methyl (3), 4-methyl (4) and the imidic O-methyl derivative (5), are described. Regioselectivity was achieved for the synthesis of (2) by addition of ethyl glycinate to the 1,3-dipolar nitrile imine derived from N- methylbenzohydrazonoyl bromide hydrobromide (8). The key step for the synthesis of (3) was addition of benzyl 3-methylcarbazate (14) to ethyl N-[ chloro (phenyl) methylene ] glycinate (15b). The 4-methyl compound (4) was prepared by cycloadditi

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10

Seitz, Gunther, та Jens Lachmann. "Synthese neuer Pyridin-, Pyrindin- bzw. Isochinolin-substituierter α- und β-C-Nukleoside der 2-Desoxy-D-ribose / Synthesis of Novel Pyridine-, Pyrindine- and Isoquinoline-Substituted α- and β-C-Nucleosides of 2-Deoxy-D-ribose". Zeitschrift für Naturforschung B 54, № 4 (1999): 549–58. http://dx.doi.org/10.1515/znb-1999-0420.

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The novel imido esters of 2-deoxy-α- and -β-D-ribose 8 and 9 have been synthesized and successfully transformed to the protected 1,2,4-triazine-C -nucleosides 11 and 12 using an inverse type Diels-Alder reaction with the 1,2,4,5-tetrazine 10. The electron deficient diazadiene system of both C -nucleosides 11 and 12 proved to be highly reactive in a consecutive [4 + 2] cycloaddition with inverse electron demand towards several electron rich dienophiles yielding after successful deprotection the novel pyridine-, pyrindine- and isoquinoline-C-nucleosides 15, 18 and 21 of 2 -deoxy-α-D-ribose and 2

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11

Saeed, Aamer, Najim A. Al-Masoudi, Amjed A. Ahmed, and Christophe Pannecouque. "New Substituted Thiazol-2-ylidene-benzamides and Their Reaction with 1-Aza-2-azoniaallene Salts. Synthesis and anti-HIV Activity." Zeitschrift für Naturforschung B 66, no. 5 (2011): 512–20. http://dx.doi.org/10.1515/znb-2011-0512.

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A series of N-(3-(substituted-alkyl- or halophenyl)-4-methylthiazol-2(3H)-ylidene)-substituted alkyl- or halo-benzamides 21 - 40 were prepared by base-catalyzed cyclization of the corresponding 1-(substituted-alkyl- or halo-benzoyl)-3-(substituted-halophenyl)thioureas 1 - 20. Substituted pyrazolo[ 4,3-d]thiazol-5(6aH)-ylidene)benzamides 45a - d were synthesized by cycloaddition of compound 45 with the reactive cumulene intermediates 42a - d. All compounds were evaluated for their antiviral activity against the replication of HIV-1 and HIV-2 in MT-4. Compounds 35 and 39 showed an IC50 of 2.02 μ

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12

Vidadala, Ramasubbarao, and Madhusudana Rao J. "Isolation, characterization and semi-synthesis of natural products dimeric amide alkaloids." Journal of Natural Products and Natural Products Synthesis 1, no. 1 (2021): 1–14. http://dx.doi.org/10.55124/jnns.v1i1.17.

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Isolation, characterization of natural products dimeric amide alkaloids from roots of the Piper chaba Hunter. The synthesis of these products using intermolecular [4+2] cycloaddition reaction has been described. Obtained products were characterized using IR, 1HNMR, 13CNMR and Mass Spectroscopy. Introduction The awesome structural diversity and complexity of natural products inspire many chemists to consider how nature creates these molecules. Nature’s biosynthetic enzymes offer a powerful and practical route to many organic compounds, and synthetic chemists sometimes seek to imitate the effici

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13

Mojica, Martha, Francisco Méndez, Julio A. Alonso, Arlette Richaud, and María J. López. "(Invited) Effect of the Electron-Donating and Electron-Withdrawing Substituent on the Diels-Alder Cycloaddition Reaction of Hemifullerenes with 1,3-Butadiene." ECS Meeting Abstracts MA2023-01, no. 12 (2023): 1274. http://dx.doi.org/10.1149/ma2023-01121274mtgabs.

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In the search for an efficient method to synthesize C60, the dimerization strategy of two C30H12 fragments has been considered (1,2). Scott et. al. (3) have demonstrated that the Diels-Alder cycloaddition reaction in the bay regions of a polycyclic aromatic hydrocarbon (PAH) can occur at low temperatures (below 150ᵒC), they have also shown that the use of nitroethylene as masked-acetylene in a DA reaction over the bay regions of perylene and 7,14-dimesitylbisanthene leads to a rapid conversion of the bay regions of the PAH to new unsubstituted benzene rings (4) .This findings allow us to think

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14

Menzek, A., and M. Balci. "Cycloheptatriene Norcaradiene Equilibrium in Dimethyl trans-3,8-Dihydroheptalene-3,8-dicarboxylate." Australian Journal of Chemistry 46, no. 10 (1993): 1613. http://dx.doi.org/10.1071/ch9931613.

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Diels-Alder cycloadditions of dienophiles , such as 4-phenyl-1,2,4-triazoline-3,5-dione, dimethyl acetylenedicarboxylate, dimethyl fumarate , diethyl azodicarboxylate , maleic anhydride, benzyne and p-benzoquinone, to dimethyl trans-3,8-dihydrohexalene-3,8-dicarboxylate (4) have been investigated, and monoaddition products (9)-(16) have been isolated. It has been shown that a second addition to this system occurs only with singlet oxygen and with benzyne. Furthermore, it has been established that the second addition is retarded because of the strain in the cycloheptatriene molecule. The anti b

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15

Stepanova, Elena V., and Andrei I. Stepanov. "SYNTHESIS AND REACTIVITY OF 4-NITRO-3-(TETRAZOL-5-YL) FURAZAN WITH N- AND O-NUCLEOPHILES." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, no. 5 (2017): 21. http://dx.doi.org/10.6060/tcct.2017605.5523.

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A rational four-stages scheme for the synthesis of 4-nitro-3-(tetrazol-5-yl)furazane is proposed. The synthesis starts from the stage of 3-amino-4-(1,2,4-oxadiazol-3-yl)-furazan preparation by condensation of amidoxime of 4-aminofurazan-3-carboxylic acid with triethyl orthoformate, further reductive ring opening of 1,2,4-oxadiazole cycle. The action of hydrazine results in amidrazone of 4-aminofurazan-3-carboxylic acid formation. On the next step the diazotization of the resulting compound with sodium nitrite in acetic acid gives 3-amino-4-(tetrazol-5-yl)furazane. At last stage the titled 4-ni

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16

Vidadala, Ramasubbarao. "Study and optimization of Diels-Alder reaction of piperine in aqueous ionic solutions using Gn.HCl as a catalyst." Journal of Green Chemistry and Chemical Engineering 1, no. 1 (2021): 1–7. http://dx.doi.org/10.55124/jgce.v1i1.18.

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V. Rama Subbaraoa* aNatural Products Laboratory, Organic Chemistry Division-I, Indian Institute of Chemical Technology, Habsiguda, Hyderabad 500007, India. Study and optimization of Diels-Alder reaction of piperine in aqueous ionic solutions using Gn.HCl as a catalyst. The semi-synthesis of these products using intermolecular [4+2] cycloaddition reaction has been described. Obtained products were characterized using IR, HNMR, CNMR and Mass Spectroscopy. Introduction An outsized number of phenomena concern to and are conducted in liquid phase involving ionic species (Mil

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17

Rybickajasinska, Katarzyna, Zuzanna Szeptuch, Hubert Kubiszewski, and Agnieszka Kowaluk. "Electrochemical Cycloaddition Reactions of Alkene Radical Cations – a Route Towards Cyclopropanes and Cyclobutanes." ECS Meeting Abstracts MA2023-01, no. 41 (2023): 2325. http://dx.doi.org/10.1149/ma2023-01412325mtgabs.

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New methods to promote single-electron transfer reactions play an increasingly important role in driving modern organic chemistry. Significant advances have been made in the field of photoredox catalysis1 and synthetic organic electrochemistry2 to expand the utility of radicals in organic synthesis.3 While the initial developments in synthetic organic electrochemistry date as far back as the early 19th century, only recently has it undergone an explosive revival and it is now an important part of synthetic organic chemistry.4 Undeniably, it provides a green alternative to known and new reactiv

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18

Möhrle, Hans, and Thomas Berkenkemper. "Oxidation von Methylpiperidin-Derivaten unter Berücksichtigung der Chiralität / Oxidation of Methylpiperidine Derivatives with Regard to Chirality." Zeitschrift für Naturforschung B 62, no. 12 (2007): 1514–24. http://dx.doi.org/10.1515/znb-2007-1208.

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When 2-(2-methyl-1-piperidinyl)ethanol derivatives 3a and 3b were dehydrogenated with Hg(II)- EDTA, an iminium function involving the tertiary α-carbon atom of the piperidine ring is formed regioselectively. Cyclization of these intermediates yielded diastereomeric mixtures of oxazolidines 7a and 7b, in solutions of which hydroxy-enamine species 8a/9a and 8b/9b, respectively, could be detected by NMR spectroscopy. A hydroxy-enamine derived from 7a could be trapped by cycloaddition to tetrazine 10. Protonation of the oxazolidines generated the iminium salts 6a/6b・X with loss of a chirality cent

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19

Sato, Masayuki, Chikara Kaneko, Yoshito Abe, Toshio Furuya, and Noriyoshi Inukai. "Synthesis of 1,3-Dioxin-4-ones and Their Use in Synthesis. 21. Intramolecular Photo[2+2]cycloaddition Reactions of Chiral Spirocyclic Dioxinones Having w-Alkenyl Groups at 3-Position." HETEROCYCLES 30, no. 1 (1990): 217. http://dx.doi.org/10.3987/com-89-s6.

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20

Song, Jin, and Liuzhu Gong. "RhII/ZnII Catalyzed Asymmetric [4+3] Cycloaddition Reaction." Chinese Journal of Organic Chemistry 40, no. 1 (2020): 245. http://dx.doi.org/10.6023/cjoc202000004.

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21

Benallou, Abdelilah, Habib El Alaoui El Abdallaoui, and Hocine Garmes. "An electron localization function analysis of the molecular mechanism and the C–O bond formation in the [3+2] cycloaddition reaction involving zwitterionic type between a nitrone and an electron deficient ethyne." Progress in Reaction Kinetics and Mechanism 45 (October 14, 2019): 146867831982574. http://dx.doi.org/10.1177/1468678319825742.

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The mechanistic nature of a [3+2] cycloaddition reaction involving zwitterionic species has been investigated, and the changes of electron density related to the O–C and C–C bond formation along the intrinsic reaction coordinate have been characterized. This polar [3+2] cycloaddition reaction, which takes place through a non-concerted two-stage one-step mechanism, proceeds with a moderate Gibbs free activation energy of 21 kcal mol−1. The reaction begins by the creation of a pseudoradical centre at the central carbon, first on the dimethyl acetylenedicarboxylate, and second on the nitrone fram

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22

Burger, Klaus, Eva Höß, Norbert Sewald, Klaus Geith, Jürgen Riede, and Peter Bissinger. "Zum Cycloadditionsverhalten von 5-Azido-4-trifluormethyl-1,3-azolen / Cycloaddition Reactions with 5-Azido-4-trifluoromethyl-1,3-azoles." Zeitschrift für Naturforschung B 45, no. 12 (1990): 1695–708. http://dx.doi.org/10.1515/znb-1990-1217.

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[3+2] Cycloaddition reactions of 5-azido-4-trifluoromethyl-1,3-azoles with various CC multiple bond systems are described. On reaction of 5-azido-4-trifluoromethylthiazoles 2 with 2,3-dimethylbuta-1,3-diene no [3+2] cycloaddition products could be isolated, 5,6-dihydro-2 H-pyrane 19 was formed exclusively. Photolysis of 1,2,3-triazoles 23, 24, obtained from 2 and electron deficient alkynes, yields imidazo[5,1-b]thiazoles 28. This photoreaction can be interpreted mechanistically as a “Thio-Cornforth-Reaction”.

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23

Li, Jian, Shangrong Zhu, Qiuneng Xu, Li Liu, and Shenghu Yan. "Brønsted acid mediated intramolecular cyclopropane ring expansion/[4 + 2]-cycloaddition." Organic & Biomolecular Chemistry 17, no. 47 (2019): 10004–8. http://dx.doi.org/10.1039/c9ob02379h.

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A cascade reaction of 3-hydroxy-2-phenylisoindolin-1-one and cyclopropyl ketone has been developed via BrØnsted acid-promoted ring-opening/intramolecular cross-cycloaddition/[4 + 2]-cycloaddition process.

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24

Yan, Yan-Mei, Hao-Yang Li, Min Zhang, et al. "One-Pot Synthesis of [1,2,3]Triazolo[1,5-a]quinoxalin-4(5H)-ones by a Metal-Free Sequential Ugi-4CR/Alkyne–Azide Cycloaddition Reaction." Synlett 31, no. 01 (2019): 73–76. http://dx.doi.org/10.1055/s-0037-1610737.

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A convenient and one-pot approach to prepare [1,2,3]triazolo[1,5-a]quinoxalin-4(5H)-ones by a metal-free sequential Ugi-4CR/alkyne–azide cycloaddition reaction has been developed. The reaction of 2-azidobenzenamines, aldehydes, propiolic acids, and isocyanides produced the Ugi adducts, which were transformed to the [1,2,3]triazolo[1,5-a]quinoxalin-4(5H)-ones in moderate to good yields via alkyne–azide cycloaddition reaction.

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25

Dvořák, Dalimil, David Šaman, Zdeněk Arnold, Ivana Císařová, and Václav Petříček. "Cycloaddition Reactions of Arylmethylenemalonaldehydes with Olefins." Collection of Czechoslovak Chemical Communications 57, no. 11 (1992): 2337–58. http://dx.doi.org/10.1135/cccc19922337.

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A series of 2,4-disubstituted 3,4-dihydro-2H-pyran-5-carboxaldehydes II-XIX was prepared by reaction of substituted arylmethylenemalonaldehydes I with 2-methylpropane, 1,1-diphenylethylene, styrene, ethyl vinyl ether, 1,1-dimethoxyethylene and 1,1-bis(methylthio)ethylene. In the case of the reaction with ethyl vinyl ether the dependence of the ratio of the arising cis- and trans- 2-ethoxy-4-aryl-3,4-dihydropyran-5-carboxaldehydes VII-XIV on the substitutent on the aromatic nucleus was studied. Information on the mechanism of this reaction was obtained and conformational equilibria of 2-ethoxy-

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26

Hostetler, Katherine J., James S. Poole, and Phillip E. Fanwick. "4-{[3,5-Bis(methoxycarbonyl)-4,5-dihydro-1H-pyrazol-5-yl]methylamino}pyridine 1-oxide monohydrate." Acta Crystallographica Section E Structure Reports Online 62, no. 7 (2006): o3015—o3016. http://dx.doi.org/10.1107/s1600536806021970.

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The title compound, C13H16N4O5·H2O, was isolated following the cycloaddition reaction of 4-azidopyridine 1-oxide with an excess of methyl acrylate. The compound arises from a reaction sequence whereby the expected triazoline product undergoes rearrangement and a second cycloaddition reaction to yield the title pyrazoline product without the presence of a strong base which is usually required for such transformations.

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27

Tsui, Jordan A., Timothy M. Bolton, and Brian T. Sterenberg. "Tungsten coordination chemistry of 1,4-bisdiphenylphosphinobutadiyne — Synthesis of coordination macrocycles and factors controlling diyne cycloaddition." Canadian Journal of Chemistry 87, no. 1 (2009): 197–204. http://dx.doi.org/10.1139/v08-123.

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The 1:1 reaction of [W(CO)4(2-picoline)2] (1) with Ph2PCtriple bondC-Ctriple bondCPPh2 (2) led to {[cis-W(CO)4]2(µ-Ph2PC4PPh2)2} (3), in which two bis(diphenylphosphino)butadiyne ligands bridge two tetracarbonyltungsten centres. Reaction of 1 with excess 2 led to [cis-W(CO)4(Ph2PC4PPh2-κ1-P)2] (4), in which two dangling bis-phosphines are coordinated to one metal centre, and reaction of 2 with two equivalents of 1 led to {[W(2-picoline)(CO)4]2(µ-Ph2PC4PPh2)} (5), in which one ligand bridges two tungsten centres. Combination of 4 and 5 led to the trimeric complex {[cis-W(CO)4]3(µ-Ph2PC4PPh2)3}

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28

Vernekar, Sanjeev Kumar V., Li Qiu, Jeana Zacharias, Robert J. Geraghty, and Zhengqiang Wang. "Synthesis and antiviral evaluation of 4′-(1,2,3-triazol-1-yl)thymidines." Med. Chem. Commun. 5, no. 5 (2014): 603–8. http://dx.doi.org/10.1039/c4md00039k.

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The Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) of 4′-azidothymidine (5) generated a series of 1,2,3-triazole analogues (9) with moderate anti-HIV activities, while a similar cycloaddition reaction catalyzed by Ru(ii) failed.

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29

Jasiński, Radomir, Michał Rzyman, and Andrzej Barański. "Conjugated nitroalkenes in cycloaddition reactions. Part 2. Diels–Alder reactions of E-2-aryl-1-cyano-1-nitroethenes with cyclopentadiene." Collection of Czechoslovak Chemical Communications 75, no. 9 (2010): 919–29. http://dx.doi.org/10.1135/cccc2009562.

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The reaction between E-2-aryl-1-cyano-1-nitroethenes 1a–1e and cyclopentadiene (2) occurs according to the carbodiene [4+2]cycloaddition scheme and leads to the corresponding 6-endo-aryl-5-endo-cyano-5-exo-nitronorbornenes 3a–3e and 6-exo-aryl-5-exo-cyano-5-endo-nitronorbornenes 4a–4e as the only reaction products. The attempts to detect the products of heterodiene [4+2]cycloaddition in the reaction environment were not successful.

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30

Stefańska, Karolina, Anna Szafraniec, Marek P. Szymański, Michał Wierzbicki, Agnieszka Szumna, and Waldemar Iwanek. "Chiral chromane[4]arenes synthesised by cycloaddition reactions ofo-quinomethine resorcin[4]arenes." New Journal of Chemistry 43, no. 6 (2019): 2687–93. http://dx.doi.org/10.1039/c8nj06179c.

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The synthesis of cavity-extended cyclochiral heterocyclic derivatives of chromane[4]arenes by a cycloaddition reaction between theo-quinomethine derivative of resorcin[4]arene and various styrenes is described.

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31

Cai, Wangshui, Junxian Wu, Haowei Zhang, Hitesh B. Jalani, Guigen Li, and Hongjian Lu. "Rh-Catalyzed Chemoselective [4 + 1] Cycloaddition Reaction toward Diverse 4-Methyleneprolines." Journal of Organic Chemistry 84, no. 17 (2019): 10877–91. http://dx.doi.org/10.1021/acs.joc.9b01466.

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32

Caraculacu, Adrian A., Elena Scorţanu, and Georgeta Caraculacu. "New Parabanate Products by 1, 3-Dipolar Cycloaddition Reaction (‘Criss-Cross’ Cycloaddition)." High Performance Polymers 11, no. 4 (1999): 477–82. http://dx.doi.org/10.1088/0954-0083/11/4/311.

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33

Harmata, Michael, Chaofeng Huang, Parham Rooshenas, and Peter R Schreiner. "An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes." Angewandte Chemie International Edition 47, no. 45 (2008): 8696–99. http://dx.doi.org/10.1002/anie.200803487.

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34

Harmata, Michael, Chaofeng Huang, Parham Rooshenas, and Peter R Schreiner. "An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes." Angewandte Chemie 120, no. 45 (2008): 8824–27. http://dx.doi.org/10.1002/ange.200803487.

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35

Bors, István, Mihály Purgel, Péter Pál Fehér, et al. "Unexpected radical mechanism in a [4+1] cycloaddition reaction." New Journal of Chemistry 45, no. 19 (2021): 8440–44. http://dx.doi.org/10.1039/d1nj00660f.

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The mechanism of the cheletropic reaction of monoimines with PPh<sub>3</sub>via unexpected radical intermediates resulting in oxazaphospholes has been discussed based on EPR, UV-vis and DFT calculations.

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36

Leblanc, Yves, Brian J. Fitzsimmons, James P. Springer, and Joshua Rokach. "[4 + 2] Cycloaddition reaction of dibenzyl azodicarboxylate and glycals." Journal of the American Chemical Society 111, no. 8 (1989): 2995–3000. http://dx.doi.org/10.1021/ja00190a037.

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37

Kametani, Tetsuji, Hajime Takeda, Yukio Suzuki, and Toshio Honda. "Synthesis of Quinoline Derivatives by [4+2]Cycloaddition Reaction." Synthetic Communications 15, no. 6 (1985): 499–505. http://dx.doi.org/10.1080/00397918508063833.

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38

Harmata, Michael, Chandra B. Gamlath, and Charles L. Barnes. "Relative stereocontrol in an intramolecular 4+3 cycloaddition reaction." Tetrahedron Letters 34, no. 2 (1993): 265–68. http://dx.doi.org/10.1016/s0040-4039(00)60563-4.

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39

Korenchenko, O. V., A. Yu Aksinenko, V. B. Sokolov, A. N. Pushin, and I. V. Martynov. "Alkoxycarbonylimines of hexafluoroacetone in reaction of [2+4]-cycloaddition." Russian Chemical Bulletin 44, no. 9 (1995): 1740–44. http://dx.doi.org/10.1007/bf01151302.

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40

Nallamala, Sirisha, Srikumar Mannem, and Raghunathan Raghavachary. "Highly Efficient Construction of Sugar-Fused Spirochromanono Pyrrolidines/Pyrrolizidines/Thiolizidines via 1,3-Dipolar Cycloaddition of Azomethine Ylides." SynOpen 01, no. 01 (2017): 0063–67. http://dx.doi.org/10.1055/s-0036-1588520.

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A variety of sugar-fused chromanono pyrrolidines/pyrrolizidines/thiolizidines have been synthesized by intermolecular 1,3-dipolar cycloaddition reaction of azomethine ylides (generated from glucose aldehyde and different secondary amino acids) with various 3-arylidene chroman-4-ones as dipolarophiles. The solvent effect on the 1,3-dipolar cycloaddition reaction is also studied.

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41

Hunnur, Raveendra K., Prashant R. Latthe, and Bharati V. Badami. "1,3-Dipolar Cycloaddition Reactions in Heterocyclic Synthesis. Synthesis of [1-[4-(thiazolyl/imidazothiazolyl/triazolyl)phenyl]-1H-pyrazole-3,4-dicarboxylate esters from 3-(4-acetylphenyl)sydnone." Journal of Chemical Research 2005, no. 9 (2005): 592–94. http://dx.doi.org/10.3184/030823405774308907.

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Cycloaddition of 3-(4-acetylphenyl)sydnone (1) with DMAD gave dimethyl 1-(4-acetylphenyl)-1H-pyrazole-3,4-dicarboxylate (2), which on bromination yielded the corresponding monobromoacetyl (3) and dibromoacetyl (4) derivatives. Both compounds 3 and 4 on reaction with thiourea and thioacetamide afforded the 2-amino- (5) and the 2-methyl- (6) thiazole derivatives respectively, while compound 3 on reaction with 2-aminothiazole gave the imidazothiazole 7. Compound 3 was converted into its azide (8), which on 1,3-dipolar cycloaddition with DMAD afforded the 1,2,3-triazole-4,5-dicarboxylate (9).

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42

Heravi, Majid M., and Vaezeh Fathi Vavsari. "Recent applications of intramolecular Diels–Alder reaction in total synthesis of natural products." RSC Advances 5, no. 63 (2015): 50890–912. http://dx.doi.org/10.1039/c5ra08306k.

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43

Fudickar, Werner, and Torsten Linker. "Intermediates in the Formation and Thermolysis of Peroxides from Oxidations with Singlet Oxygen." Australian Journal of Chemistry 67, no. 3 (2014): 320. http://dx.doi.org/10.1071/ch13423.

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Herein we describe the recent mechanistic understandings of the singlet oxygen ene reaction to give hydroperoxides and the [4+2] cycloaddition affording endoperoxides. Both experimental findings and theoretical work conclude in the formation of intermediates structurally similar to perepoxides during the ene reaction. Such intermediates mainly control the regio- and stereoselectivities of this reaction class. For the [4+2] cycloaddition, both a synchronous concerted reaction (benzene, naphthalenes) and a stepwise reaction with a non-symmetric zwitterionic intermediate (larger acenes) have been

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44

Wu, Di, Rakesh Ganguly, Yongxin Li, Sin Ni Hoo, Hajime Hirao, and Rei Kinjo. "Reversible [4 + 2] cycloaddition reaction of 1,3,2,5-diazadiborinine with ethylene." Chemical Science 6, no. 12 (2015): 7150–55. http://dx.doi.org/10.1039/c5sc03174e.

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45

Li, Yan, та Shiwen Du. "Understanding the mechanisms, regioselectivies and enantioselectivities of the DMAP-catalyzed [2 + 4] cycloaddition of γ-methyl allenoate and phenyl(phenyldiazenyl)methanone". RSC Advances 6, № 87 (2016): 84177–86. http://dx.doi.org/10.1039/c6ra16321a.

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46

Wingert, Horst, and Manfred Regitz. "Synthesen mit Cyclobutadienen, 14 [1]. Tetra-tert-butylprismane durch Dewarbenzol-Isomerisierung / Syntheses with Cyclobutadienes, 14 [1]. Tetra-tert-butylprismanes by Dewarbenzene-Isomerization." Zeitschrift für Naturforschung B 41, no. 10 (1986): 1306–10. http://dx.doi.org/10.1515/znb-1986-1018.

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The kinetically stabilized cyclobutadiene 2 undergoes [4+2]-cycloaddition reaction at elevated temperature with the acetylenecarboxylate 3 to yield the regioisomeric dewarbenzenes 5 and 6. They are transformed into the prismanes 7 and 8 by a photochemical intramolecular [2+2]- cycloaddition process. Under thermal conditions (150 °C) this isomerization reaction is reversible (7→5, 8→6).

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47

Tsutsui, Ayumi, Ambara R. Pradipta, Elena Saigitbatalova, Almira Kurbangalieva, and Katsunori Tanaka. "Exclusive formation of imino[4 + 4]cycloaddition products with biologically relevant amines: plausible candidates for acrolein biomarkers and biofunctional modulators." MedChemComm 6, no. 3 (2015): 431–36. http://dx.doi.org/10.1039/c4md00383g.

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48

Sleziak, Róbert, and Alžbeta Krutošíková. "Cycloaddition Reactions of Furo[2,3-b]pyrroles." Collection of Czechoslovak Chemical Communications 64, no. 2 (1999): 321–28. http://dx.doi.org/10.1135/cccc19990321.

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Reactions of furo[2,3-b]pyrroles with dimethyl butynedioate and ethyl propynoate were investigated. The reaction course is influenced by the substituents on the fused system. Products of [4+2]cycloaddition to the furan ring leading to indole derivatives have been observed. In the case of the reaction of methyl 6H-furo[2,3-b]pyrrole-5-carboxylate (1a) with dimethyl butynedioate, products of [4+2]cycloaddition to the furan ring as well as of Michael addition to the pyrrole ring leading to N-substituted indole derivative 3 have been observed.

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49

Gonçalves, Azambuja, Davi, et al. "Ethyl 6-Methyl-2-oxo-4-{4-[(1-phenyl-1H-1,2,3-triazol-4-yl)methoxy]phenyl}-1,2,3,4-tetrahydropyrimidine-5-carboxylate." Molbank 2019, no. 3 (2019): M1076. http://dx.doi.org/10.3390/m1076.

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The Biginelli reaction is an acid-catalyzed, three-component reaction between an aldehyde, a hydrogen methylene active compound, and urea (or its analogue) and constitutes a rapid and easy synthesis of highly functionalized heterocycles. Synthesis of ethyl 6-methyl-2-oxo-4-{4-[(1-phenyl-1H-1,2,3-triazol-4-yl)methoxy]phenyl}-1,2,3,4-tetrahydropyrimidine-5-carboxylate, identified by our laboratory code LaSOM® 293, was achieved using the Biginelli reaction as the key step, followed by the Huisgen 1,3-dipolar cycloaddition in a convergent four-step route. The product LaSOM® 293 was obtained with a

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50

Kumar, Raju Suresh, Dhaifallah M. Al-thamili, Abdulrahman I. Almansour, Natarajan Arumugam, and Necmi Dege. "[Bmim]Br Accelerated One-Pot Three-Component Cascade Protocol for the Construction of Spirooxindole–Pyrrolidine Heterocyclic Hybrids." Molecules 25, no. 20 (2020): 4779. http://dx.doi.org/10.3390/molecules25204779.

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Our synthetic approach for the assembly of structurally complex spirooxindole heterocyclic hybrids was based on an ionic liquid, [bmim]Br mediated one-pot three-component cascade reaction strategy involving 1,3-dipolar cycloaddition reaction of N-1-(2-pyridinylmethyl)-3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones and azomethine ylide generated in situ from isatin and L-phenyl alanine, affording a series of spirooxindole–pyrrolidine heterocyclic hybrids in good-to-excellent yields. In addition to serving as the reaction medium, [bmim]Br also functioned as a catalyst in this cycloaddi

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