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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...

Data: 2004 | Origem: Estudo Geral - Universidade de Coimbra

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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...

Data: 2002 | Origem: Estudo Geral - Universidade de Coimbra

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