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Cycloaddition of trifluoromethyl azafulvenium methides: synthesis of new triflu...
Nunes, Cláudio M.; Silva, Manuela Ramos; Beja, Ana Matos; Fausto, Rui; Melo, Teresa M.V.D. Pinho eThe chemistry of trifluoromethyl azafulvenium methides was explored leading to a new route to trifluoromethylpyrrole-annulated systems. The first evidence of azafulvenium methides acting as 1,3-dipoles is reported. These azafulvenium methides showed site selectivity in the reaction with strong electron-deficient dipolarophiles leading exclusively to 1,3-cycloadducts. In the cycloaddition with less-activated dip...
4-Halo-1,3-oxazoles: Unambiguous structural assignment of 2-halo-2-benzoyl-2H-a...
Lopes, Susy; Nunes, Cláudio M.; Fausto, Rui; Melo, Teresa M. V. D. Pinho ehttp://www.sciencedirect.com/science/article/B6TGS-4T9CD1T-2/2/97ced5a20f3a7c031b52a8483cc8ee76
Spectroscopic and theoretical investigation of the conformational space of a py...
Nunes, Cláudio M.; Lopes, Susy; Melo, Teresa M. V. D. Pinho e; Fausto, Ruihttp://www.sciencedirect.com/science/article/B6TGS-4V88FW3-1/2/a0eb253493e1ccafe49b75247f2ded74
Chemistry of Diazafulvenium Methides in the Synthesis of Functionalized Pyrazoles
Melo, Teresa M. V. D. Pinho e; Nunes, Cláudio M.; Soares, Maria I. L.; Paixão, José A.; Beja, Ana Matos; Silva, Manuela RamosThe chemistry of diazafulvenium methides generated by the thermal extrusion of sulfur dioxide from 2,2-dioxo-1H,3H-pyrazolo[1,5-c] [1,3]thiazoles is described. The diazafulvenium methides unsubstituted at C-7 participate in [8π + 2π] cycloadditions giving pyrazolo-annulated heterocycles resulting from the addition across the 1,7-position. 1-Methyl-diazafulvenium methides and 7,7-dimethyl-diazafulvenium methides...
1,3-Dipolar cycloaddition of azomethine ylides generated from aziridines in sup...
Gomes, Paulo J. S.; Nunes, Cláudio M.; Pais, Alberto A. C. C.; Melo, Teresa M. V. D. Pinho e; Arnaut, Luis G.The 1,3-dipolar cycloaddition of azomethine ylides with DMAD in supercritical carbon dioxide is reported. The photolysis reaction conditions were optimized with a suitable adjustment of pressure, temperature, irradiation time and co-solvent concentration leading to a more efficient reaction than in neat acetonitrile. Similar results were observed using thermal reaction conditions. Supercritical carbon dioxide w...
On the photophysical behaviour of 4-halo-5-phenylisoxazoles
Fonseca, Sofia M.; Burrows, Hugh D.; Nunes, Cláudio M.; Melo, Teresa M. V. D. Pinho e; Gonsalves, António M. d'A. RochaDetailed spectral and photophysical properties of 4-halo-5-phenylisoxazoles in cyclohexane solutions are presented, including measurements of energies of lowest excited singlet and triplet states, fluorescence quantum yields, lifetimes, phosphorescence and triplet-singlet difference absorption spectra. Upon addition of ethanol, loss of vibrational structure is observed in fluorescence spectra and attributed to ...
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