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Synthesis of tricyclic isoindoles and thiazolo[3,2-c][1,3]benzoxazines
Pinho e Melo, Teresa M. V. D.; Santos, Catarina I. A.; Rocha Gonsalves, António M. dA.; Paixão, José A.; Beja, Ana M.The thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in Ac2O led to novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles and chiral (9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindoles were obtained on FVP. Starting from -cysteine methyl ester (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazines were obtained as single stereoisomers. The t...
Oxidation of Δ4- and Δ5-Steroids with Hydrogen Peroxide Catalyzed by Porphyrin ...
Rebelo, Susana L. H.; Simões, Mário M. Q.; Neves, M. Graça P. M. S.; Silva, Artur M. S.; Cavaleiro, José A. S.; Peixoto, Andreia F.In this paper we describe a new environmentally friendly method to promote the stereoselective epoxidation of Delta4- and Delta5-steroids. Metalloporphyrins efficiently catalyze the epoxidation reactions of 17beta-acetoxy-4-androstene (1), 4-cholestene (2) and 3beta-acetoxy-5-cholestene (3) in the presence of H2O2 as oxygen donor. Modeling the molecular structure of the porphyrin as well as the central metal al...
Novel Asymmetric Wittig Reaction: Synthesis of Chiral Allenic Esters
Melo, Teresa M. V. D. Pinho e; Cardoso, Ana L.; Gonsalves, António M. d'A. Rocha; Pessoa, João Costa; Paixão, José A.; Beja, Ana M.Wittig reactions between 10-(phenylsulfonyl)isobornyl (triphenylphosphoranylidene)acetates (1 and 6) and ketenes resulted in asymmetric induction, with the selective synthesis of allenes with axial chirality. Use of the (1R)-(-)-10-(phenylsulfonyl)isoborneol unit allows the synthesis of allenes with S configuration, whereas use of the (1S)-(+)-10-(phenylsulfonyl)isoborneol unit produces allenes with R configura...
Synthesis of novel tricyclic isoindole derivatives
Melo, Teresa M. V. D. Pinho e; Santos, Catarina I. A.; Gonsalves, António M. d'A. Rocha; Paixão, José A.; Beja, Ana M.; Silva, Manuela RamosNovel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles were prepared from the thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in acetic anhydride. The structure of 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindole 6a was determined by X-ray crystallography. ; http://www.sciencedirect.com/science/article/B6THS-49PXCD9-X/1/45bd0f04f44115a1e7b644d727569da1
Contribution to the synthesis of chiral allenic esters
Melo, Teresa M. V. D. Pinho e; Cardoso, Ana L.; Gonsalves, António M. D'A. Rocha; Storr, Richard C.; Pessoa, João Costa; Paixão, José A.; Beja, Ana M.A phosphorus ylide bearing a 10-phenylsulfonylisoborneol unit reacted with ketenes, generated in situ from acid chlorides and triethylamine, to give allenic compounds. The reaction with methylketene led to asymmetric induction with the selective synthesis of an allene with axial chirality corresponding to an S configuration. The structure of the chiral allene 10-phenylsulfonylisobornyl penta-2,3-dienoate was de...
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...
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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