Oxidation of Delta(4)- and Delta(5)-steroids with hydrogen peroxide catalyzed by porphyrin complexes of Mn-III and Fe-III

• Tipo: Artigo em Revista Científica Internacional
• Data: 2004

Autores

Susana L H Rebelo (Autor) Outra; Simoes, MMQ (Autor) Outra; Neves, MGPMS (Autor) Outra; Silva, AMS (Autor) Outra; Cavaleiro, JAS (Autor) Outra; Peixoto, AF (Autor) FCUP; Pereira, MM (Autor) Outra; Silva, MR (Autor) Outra; Paixao, JA (Autor) Outra; Beja, AM (Autor) Outra

Revista

Título: European Journal of Organic Chemistry

Vol. 2004

Páginas: 4778-4787

ISSN: 1434-193X

Editora: Wiley-Blackwell

Indexação

ISI Web of Knowledge - 34 Citações

Scopus - 35 Citações

Outras Informações

ID Authenticus: P-000-7NR

DOI: 10.1002/ejoc.20040461

Abstract (EN): In this paper we describe a new environmentally friendly method to promote the stereoselective epoxidation of Delta(4)- 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 allows the control of the preferential formation of alpha- or beta-epoxides. Porphyrins with bulky, electron-withdrawing groups in the ortho positions of the meso phenyls and with Mn-III as the central metal ion, such as [Mn(TDCPP)C1], gave preferentially the beta-epoxide of Delta4- and Delta5-steroids. [Fe(TPFPP)C1] catalyzes preferentially the alpha-epoxidation of Delta(4)-steroids and also increases the stereoselectivity for the alpha-epoxide in Delta(5)-steroids, similar to the results obtained with m-CPBA (m-chloroperbenzoic acid) as oxidant. The substrate structure strongly influences the chemo selectivity of the reactions. The X-ray structures of two main products were determined, and two-dimensional NMR techniques allowed the full assignment of H-1 and C-13 NMR resonances as well as the stereochemistry of these products. A mechanistic proposal involving oxo species for the beta-approach and peroxy species for the a-approach is proposed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 10