Search results for "Diels alder"

Cycloaddition reactions of 1-tert-butyl-4-vinylpyrazole

1989

1-tert-Butyl-4-vinylpyrazole1 a reacts with dimethyl acetylenedicarboxylate (DMAD), methyl propiolate (MP) and N-phenylmaleimide (NPMI) affording the indazole derivatives2,3, and5 as a result of a Diels-Alder ([4 + 2]) cycloaddition. With diethylazodicarboxylate (DEAZD), tetracyanoethylene (TCNE) and 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) the reaction takes place exclusively through the olefinic substituent and the adducts6,7, and9 were isolated. The alkenylpyrazoles1 b–d reacted withDMAD and N-phenylmaleimide to give polymers.

ChemInform Abstract: Diels-Alder Reactions of Methyl- and π-Acceptor-Substituted 2- Vinylindoles with Dimethyl Acetylenedicarboxylate and Tetracyanoe…

2010

The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.

Diels-alder reactions of methyl- and π-acceptor-substituted 2-vinylindoles with dimethyl acetylenedicarboxylate and tetracyanoethylene: Novel functio…

1991

The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.

Understanding the regioselectivity in hetero Diels–Alder reactions. An ELF analysis of the reaction between nitrosoethylene and 1-vinylpyrrolidine

2013

[EN] The regioselectivity in the hetero Diels-Alder reaction between nitrosoethylene 1 and 1-vinylpyrrolidine 2 has been studied by a comparative ELF bonding analysis along the IRC of the endo/ortho and endo/meta regioisomeric channels at the B3LYP/6-31G*. level. Along the most favorable endo/ortho regioisomeric channel, the C-C sigma bond is first formed by coupling of two pseudoradical centers located at the most electrophilic carbon of 1 and the most nucleophilic center of 2. Formation of these relevant pseudoradical centers, which depend on the total charge transfer process along the polar reaction, and not on the approach mode of each reagent, is well characterized by analysis of the a…

Diels-Alder Reactions of Tetraphenylcyclopentadienones in Nanochannels: Fabrication of Nanotubes from Hyperbranched Polyphenylenes

2005

Efficient microwave-mediated synthesis of fullerene acceptors for organic photovoltaics

2014

Two different processes, namely the Bamford–Stevens and [4 + 2] Diels Alder reactions, have been optimized under microwave irradiation for the functionalization of fullerenes. In this manner, all the main C60- and C70-based acceptor derivatives for organic solar cells such as PCBM, DPM, BHN and ICBA, have been prepared in higher yields and shorter reaction times with respect to the reported data. These findings represent a step forward toward the wide production of cheaper organic solar cells as a consequence of the cost abatement of the acceptors given by higher yields, lower waste production, and reduced reaction time which means a strong energy saving.

On the enhancement of stereoselection by cooperation between chiral auxiliaries. Asymmetric diels-alder reactions with fumaric acid bis ((S)-proline …

1989

Abstract Fumaric acid bis ((S)-proline benzyl ester) amide reacts with cyclopentadiene in thermal and Lewis acid catalyzed Diels-Alder reactions to give the cycloadducts with high yields and diastereomeric ratios up to 100:1.

Diels-Alder Reactions ofin situ generated N-benzoylindolo-2,3-quinodimethane with carbodienophiles

1993

The indolo-2,3-quinodimethane (5), generated from 2,3-bis(bromomethyl)indole (4), was trapped with unsymmetrical carbodienophiles or N, N′-p-phenylenedimaleimide to furnish the 1,2,3,4-tetrahydrocarbazoles (6–9). [4 + 2]-Cycloaddition of 5 with tetracyanoethylene gave rise to the tetracyanocarbazole (10) and a subsequent product 11a or 11b. The Diels-Alder reaction of 5 with divinyl sulfone was regiospecific within the detection limits of HPLC analysis. Similarly, the reaction of 5 with N, N′-p-phenylenedimaleimide yielded solely the stereoisomer 9.

A retro Diels–Alder method for the preparation of pyrrolo[1,2-a]pyrimidinediones from diexo-aminooxanorbornenecarboxamide

2006

Abstract Through the reactions of diexo-3-amino-7-oxanorbornene-2-carboxamide 1 with the oxocarboxylic acids: 4-oxopentanoic acid, p-chlorobenzoylpropionic acid or 2-formylbenzoic acid, the pyrrolo[1,2-a]pyrimidinediones 2 and 3 or pyrimido[1,2-a]isoindoledione 4 were formed on cyclization and thermolysis, when the parent cycles decomposed via the loss of furan to give 2–4 in a retro Diels–Alder reaction. With cis-or trans-2-aroylcyclohexanecarboxylic acids as starting compounds, the 1-aroylhexahydroisoindol-3-ones (5–8) were formed; the phenyl-substituted derivatives gave diastereomeric mixtures. The structures of the new compounds were established by NMR spectroscopy and, for 3 and 6, als…

Ionic liquids and microwave irradiation as synergistic combination for polar Diels–Alder reactions using properly substituted heterocycles as dienoph…

2012

For the DA reactions between nitropyrrole derivatives and isoprene, the combination of microwave irradiation and protic ionic liquid, has a notable synergistic effect. DFT calculations suggest that a supplementary energy ranking in the IR region of 1700-1400 cm-1 can favour the structural changes in the reactants to reach the TS. Fil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina Fil: Ormachea, Carla. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa F…