Encontrados 8 documentos, a visualizar página 1 de 1
Nitrogen-Bridged Heterocycles via Cycloaddition of Non-Classical Heterocyclicfu...
Soares, Maria I. L.; Gomes, Clara S. B.; Melo, Teresa M. V. D. Pinho eThe [4π+2π] cycloaddition of non-classical heterocyclic-fused-[c]thiazoles was explored allowing the synthesis of a range of new nitrogen-bridged bi-, tri- and tetracyclic heterocyclic compounds namely, pyrazolo[1,5-a]pyridines, thiazolo[2,3,4-cd]pyrrolizines and indolizines. For the first time, one non-classical pyrrolo[1,2-c]thiazole was isolated and its structure determined by X-ray crystallography.
Microwave-assisted generation and reactivity of aza- and diazafulvenium methide...
Soares, Maria I. L.; Melo, Teresa M. V. D. Pinho eAzafulvenium methides and diazafulvenium methides have been generated under microwave irradiation from 2,2-dioxo-1H,3H-pyrrolo[1,2-c]thiazoles and 2,2-dioxo-1H,3H-pyrazolo[1,5-c]thiazoles, respectively. Pericyclic reactions of these 1,7-dipole intermediates, namely, sigmatropic [1,8]H shifts, 1,7-electrocyclization or [8[pi]+2[pi]] cycloaddition led to the synthesis of a range of pyrrole and pyrazole derivative...
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...
New chemistry of diazafulvenium methides: one way to pyrazoles
Melo, Teresa M. V. D. Pinho e; Soares, Maria I. L.; Gonsalves, António M. d'A. RochaDiazafulvenium methides generated from the solution pyrolysis of pyrazolo[1,5-c][1,3]thiazole-2,2-dioxides participate in [8[pi]+2[pi]] cycloadditions giving pyrazolo[1,5-a]pyridine derivatives. 1-Methyl-diazafulvenium, generated under flash vacuum pyrolysis reaction conditions, undergoes an intramolecular sigmatropic [1,8]H shift giving 1-vinyl-1H-pyrazoles. ; http://www.sciencedirect.com/science/article/B6...
N-Vinyl- and C-Vinylpyrroles from Azafulvenium Methides. Flash Vacuum Pyrolysis...
Melo, Teresa M. V. D. Pinho e; Soares, Maria I. L.; Gonsalves, António M. d'A. Rocha; Paixão, José A.; Beja, Ana Matos; Silva, Manuela Ramos1-Azafulvenium methides, generated from pyrrolo[1,2-c]thiazole-2,2-dioxides' thermal extrusion of sulfur dioxide, led to the synthesis of functionalized pyrroles. The intramolecular trapping of these transient 8π 1,7-dipoles in pericyclic reactions, namely sigmatropic [1,8]H shifts and 1,7-electrocyclization, allowed the synthesis of N-vinylpyrroles and C-vinylpyrroles which, under flash vacuum pyrolysis condit...
Reactivity of azafulvenium methides derived from pyrrolo[1,2-c]thiazole-2,2-dio...
Melo, Teresa M. V. D. Pinho e; Soares, Maria I.L.; Gonsalves, António M. D'A. Rocha; McNab, HamishExtrusion of sulfur dioxide from pyrrolo[1,2-c]thiazole-2,2-dioxides led to the synthesis of functionalised pyrroles via the generation of 1-azafulvenium methides. Sealed tube reaction conditions allowed the synthesis of N- and C-vinylpyrroles whereas from FVP methyl 1,3-dimethyl-5-oxo-5H-pyrrolizine-2-carboxylate and 4-oxo-1,4-dihydro-1-aza-benzo[f]azulene-3-carboxylates were obtained. These last compounds cou...
Synthesis of Chiral Pyrrolo[1,2-c]thiazoles via Intramolecular Dipolar Cycloadd...
Melo, Teresa M. V. D. Pinho e; Soares, Maria I. L.; Gonsalves, António M. d'A. Rocha; Paixão, José A.; Beja, Ana M.; Silva, Manuela RamosIntramolecular dipolar cycloaddition of bicyclic münchnones, 5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olates, derived from cyclodehydration of 2-substituted-N-acylthiazolidine-4-carboxylic acids are reported. A range of new pyrrolo[1,2-c]thiazole derivatives (7, 14, 15, 20, 23, and 26) were obtained as single enantiomers from 2-phenylthiazolidines, 2-benzoylthiazolidines, and 2-methylthiazolidine-4-carboxylates. Pyr...
Intermolecular Dipolar Cycloaddition Reactions of 5H,7H-Thiazolo[3,4-c]oxazol-4...
Melo, Teresa M. V. D. Pinho e; Soares, Maria I. L.; Barbosa, Dália M.; Gonsalves, António M. d'A. Rocha; Beja, Ana Matos; Paixão, José A.(5R)-3-Methyl-5-phenyl-5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olate was generated in the presence of a range of dipolarophiles. The intermolecular 1,3-dipolar cycloaddition of this mesoionic species led to the synthesis of chiral 1H-pyrrolo[1,2-c]thiazole derivatives 7a, 7b, 8, 14, 18, 19 and 20. In the reaction with methyl and ethyl vinyl ketone, spiro compounds 9 and 15 were also obtained. The structure of compo...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||