Search results for "Cycloaddition"
showing 10 items of 392 documents
Why do Electron-Deficient Dienes React Rapidly in Diels?Alder Reactions with Electron-Deficient Ethylenes? A Density Functional Theory Analysis
2004
The Diels−Alder reaction of the electron-deficient (ED) dimethyl 2,3-dimethylenesuccinate with two electron-rich (ER) and two ED ethylenes has been studied at the B3LYP/6-31G* level of theory. The analysis of the geometry and electronic structure of the transition state of the reaction with the ED dimethyl 2-methylenemalonate along with the analysis of the global and local electrophilicity indices of the reagents provide an explanation of the participation of this ED diene as nucleophile against powerful electrophiles in polar Diels−Alder reactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Density Functional Theory Study of the Cycloaddition Reaction of Furan Derivatives with Masked o-Benzoquinones. Does the Furan Act as a Dienophile in…
2002
The molecular mechanism for the cycloaddition reaction between 2-methylfuran and a masked o-benzoquinone has been characterized using quantum mechanical calculations at the B3LYP/6-31G theory level. An analysis of the results on the reaction pathway shows that the reaction takes place along a polar stepwise mechanism. The first and rate-determining step corresponds to the nucleophilic attack of the furan ring on the doubly conjugated position of the 2,4-dienone system present at the masked o-benzoquinone to give a zwitterionic intermediate. Closure of this intermediate affords the formally [2 + 4] cycloadduct. For the second step two reactive channels have been characterized corresponding t…
Unveiling the Substituent Effects in the Stereochemistry of [3+2] Cycloaddition Reactions of Aryl‐ and Alkyldiazomethylphosphonates with Norbornadien…
2021
Novel bis(tetrahydropyrrolo[3,4-b]carbazoles) linked with aliphatic chains: synthesis and structural aspects
2001
Syntheses of novel bis(tetrahydropyrrolo[3,4-b]carbazoles) by a [4+2]cycloaddition reaction are described. By variation of dienophiles bis(tetrahydropyrrolo[3,4-b]carbazoles) of varying aliphatic spacer length could be obtained in high yields. These conformationally highly flexible molecules represent an interesting class of compounds, believed to have an affinity towards DNA, as potential DNA ligands.
ChemInform Abstract: Tandem Reactions of 1,2,4-Oxadiazoles with Allylamines.
2011
Two novel thermal rearrangements are presented: the addition of allylamine (II) to oxadiazoles proceeds via ring-opening followed by cycloaddition.
ChemInform Abstract: New Studies and a Reinvestigation on (4 + 2) Cycloadditions of (-)- Thebaine: Asymmetrical Diels-Alder Reactions with a Conforma…
2010
Some novel Diels-Alder reactions of the opium alkaloid (−)-thebaine (1) as an electron-rich diene and a reinvestigation of its reactions with cyclic and acyclic dienophiles are described. The π-facial selectivity has been studied on the basis of structural analyses of the cycloadducts. Some related results on [4 + 2] cycloaddition reactions of 1-methoxy-1,3-cyclohexadiene (11) are also reported.
Theoretical Study of the 1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides. A DFT Study of Reaction between Trifluoromethyl Thiomethyl Azometh…
1999
The molecular mechanism for the 1,3-dipolar cycloaddition of trifluoromethyl thiomethyl azomethine ylide with acronitrile has been characterized using density functional theory methods with the B3L...
Intramolecular Cycloaddition Azomethine Ylides and α-(Trifluoromethyl)styrenes as Dipolarophiles
2019
ChemInform Abstract: Water-Soluble Palladium Nanoparticles: Click Synthesis and Applications as a Recyclable Catalyst in Suzuki Cross-Couplings in Aq…
2011
Polyethylene glycol-tagged macrocycle (I) is prepared by a three-fold copper-catalyzed [3 + 2] cycloaddition reaction.
ChemInform Abstract: A Modular Synthesis of Polysubstituted Indolizines.
2013
Title compounds are synthesized by [3 + 2] cycloaddition of nitroalkenes (IV) with pyridinium salts.