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Cycloaddition reactions of 3-aryl-5-phenyl-5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-...
Melo, Teresa M. V. D. Pinho e; Gomes, Clara S. B.; Gonsalves, António M. d'A. Rocha; Paixão, José A.; Beja, Ana M.; Silva, Manuela RamosIntermolecular 1,3-dipolar cycloaddition of (5R)- and (5S)-3,5-diphenyl-5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olates, (5R)- and (5S)-3-(p-methoxyphenyl)-5-phenyl-5H,7H-thiazolo-[3,4-c]oxazol-4-ium-1-olates with a range of dipolarophiles is described. New chiral 5-aryl-3-phenyl-1H,3H-pyrrolo[1,2-c]thiazoles with R and S configuration were obtained. The structure of methyl (3R)-3-phenyl-5-(p-methoxyphenyl)-1H,3H-py...
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...
Reactivity of 2-Halo-2H-azirines. 1. Reactions with Nucleophiles
Melo, Teresa M. V. D. Pinho e; Lopes, Cláudia S. J.; Gonsalves, António M. d'A. Rocha; Beja, Ana M.; Paixão, José A.; Silva, Manuela R.Nucleophilic substitution reactions of 2-halo-2H-azirines 1a, 1b, 1d, and 1e with potassium phthalimide and aniline allowed the preparation of new substituted 2H-azirines 2−5. The reactions of 2-bromo-2H-azirine 1a with methylamine led to the synthesis of α-diimines 7 and 8. 2-Halo-2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 1...
(R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine: an N-aryl pyrrolidine lig...
Gonsalves, António Manuel d'Albuquerque Rocha; Serra, Maria Elisa da Silva; Silva, Manuela Ramos; Beja, Ana Matos; Paixão, José AntónioThe N-aryl pyrrolidine diphosphine (R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine was obtained from natural tartaric acid. Contrary to our preliminary expectations, this new chiral ligand proved to be less selective than the corresponding N-benzyl pyrrolidine diphosphine. An attempted explanation of the observed behaviour based on the stereochemistry of the ligand as shown by X-ray crystallography is pres...
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...
Crystal structure of hydrated diphenylguanidinium hexafluoroferrate (III)
Silva, Manuela Ramos; Beja, Ana Matos; Costa, Benilde F. O.; Paixão, José A.; Veiga, Luiz Alte daThe crystal structure of 3C13H14N3+FeF63-·3.5H2O was determined. Both phenyl rings of the diphenylguanidine cation are oriented syn to the central C=NH2 group. The anions and cations are held together by a three-dimensional network of hydrogen bonds. In the synthesis of this compound, a second phase (iron trifluoride trihydrate) was formed and identified by powder diffraction data. Mössbauer results show two di...
A New Route to Cross-Conjugated Bis(enamines) and an Unusual Reaction with DDQ
Melo, Teresa M. V. D. Pinho e; Cabral, Ana M. T. D. P. V.; Gonsalves, António M. d'A. Rocha; Beja, Ana M.; Paixão, José A.; Silva, Manuela R.http://dx.doi.org/10.1021/jo9901384
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