Author
Gilson DeFreitas-Silva
Other affiliations: Duke University, Federal University of Bahia
Bio: Gilson DeFreitas-Silva is an academic researcher from Universidade Federal de Minas Gerais. The author has contributed to research in topics: Cyclohexanol & Catalysis. The author has an hindex of 12, co-authored 21 publications receiving 462 citations. Previous affiliations of Gilson DeFreitas-Silva include Duke University & Federal University of Bahia.
Topics: Cyclohexanol, Catalysis, Cyclohexane, Manganese, Chemistry
Papers
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TL;DR: A new methodological approach was used to describe the MnP lipophilicity, using the conventional log P(OW) means, for a series of biologically active ortho and meta isomers of Mn(III) N-alkylpyridylporphyrins, which parallels the increased efficacy in several oxidative-stress injury models, particularly those of the central nervous system.
61 citations
TL;DR: In this article, the authors reported the immobilization of different cationic and neutral metalloporphyrins on silica-coated Fe 3 O 4 nanoparticles, obtained by basic hydrolytic sol-gel process.
Abstract: In this paper we report the immobilization of different cationic and neutral metalloporphyrins (MPs) on silica-coated Fe 3 O 4 nanoparticles, obtained by basic hydrolytic sol–gel process. We characterized the MP-immobilized materials by UV–vis spectroscopy (UV–vis), X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We achieved 100% and 2% immobilization of cationic and neutral MPs, respectively. The strong electrostatic interactions between the hydroxylated surface of the silica and the positive charges of the cationic MPs favored immobilization of the charged MPs; the neutral MP probably established a weak bond with the silica and easily leached from the support. We investigated the catalytic activity of the immobilized MPs in the oxidation of cyclooctene, cyclohexene, and cyclohexane using iodosylbenzene as oxygen donor. We used the immobilized MPs in at least five successive cyclooctene oxidation reactions – the yields did not decrease, confirming that the catalyst can be reused. The synthesized catalysts displayed magnetic properties, which allowed their fast separation from the reaction medium using a simple magnet.
56 citations
TL;DR: The revised structure-activity relationships accounting for the critical importance of electrostatics in the Mn porphyrin-based redox modulation systems are presented and it is shown that the design of effective SOD mimics (per se) based on anionic p Morphyrins is greatly hindered by inappropriate Electrostatics.
55 citations
TL;DR: It is shown that the Mn(III)/Mn(II) reduction potentials are inappropriate predictors of P450-type activity of Mn porphyrin-catalyzed oxidations and shows a bell-shaped behavior.
51 citations
TL;DR: This work shows that exceptionally high k(cat) for the O2*- disproportionation can be achieved not only with an N(5)-type coordination motif, as rationalized previously for aza crown ether (cyclic polyamines) complexes, but also with a N(4)-type motif as in the Mn porphyrin case.
44 citations
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666 citations
TL;DR: This critical review focuses on metalloporphyrin-catalysed saturated C-H bond functionalisation reported since the year 2000, including C-O, C-N and C-C bond formation via hydroxylation, amination and carbenoid insertion, respectively, together with a brief description of previous achievements.
Abstract: The recent surge of interest in metal-catalysed C-H bond functionalisation reactions reflects the importance of such reactions in biomimetic studies and organic synthesis. This critical review focuses on metalloporphyrin-catalysed saturated C-H bond functionalisation reported since the year 2000, including C-O, C-N and C-C bond formation via hydroxylation, amination and carbenoid insertion, respectively, together with a brief description of previous achievements in this area. Among the metalloporphyrin-catalysed reactions highlighted herein are the hydroxylation of steroids, cycloalkanes and benzylic hydrocarbons; intermolecular amination of steroids, cycloalkanes and benzylic or allylic hydrocarbons; intramolecular amination of sulfamate esters and organic azides; intermolecular carbenoid insertion into benzylic, allylic or alkane C-H bonds; and intramolecular carbenoid C-H insertion of tosylhydrazones. These metalloporphyrin-catalysed saturated C-H bond functionalisation reactions feature high regio-, diastereo- or enantioselectivity and/or high product turnover numbers. Mechanistic studies suggest the involvement of metal-oxo, -imido (or nitrene), and -carbene porphyrin complexes in the reactions. The reactivity of such metal-ligand multiple bonded species towards saturated C-H bonds, including mechanistic studies through both experimental and theoretical means, is also discussed (244 references).
503 citations
TL;DR: A comprehensive overview of the chemical properties and some in vivo effects observed with various classes of compounds with a special emphasis on porphyrin-based compounds is provided.
Abstract: Oxidative stress has become widely viewed as an underlying condition in a number of diseases, such as ischemia–reperfusion disorders, central nervous system disorders, cardiovascular conditions, cancer, and diabetes. Thus, natural and synthetic antioxidants have been actively sought. Superoxide dismutase is a first line of defense against oxidative stress under physiological and pathological conditions. Therefore, the development of therapeutics aimed at mimicking superoxide dismutase was a natural maneuver. Metalloporphyrins, as well as Mn cyclic polyamines, Mn salen derivatives and nitroxides were all originally developed as SOD mimics. The same thermodynamic and electrostatic properties that make them potent SOD mimics may allow them to reduce other reactive species such as peroxynitrite, peroxynitrite-derived CO3·−, peroxyl radical, and less efficiently H2O2. By doing so SOD mimics can decrease both primary and secondary oxidative events, the latter arising from the inhibition of cellular tra...
434 citations
TL;DR: This review describes most successful mitochondrially-targeted redox-active compounds, Mn porphyrins and MitoQ(10) in detail, and briefly addresses several other compounds that are either catalysts of O(2)(-) dismutation, or its non-catalytic scavengers, and that reportedly attenuate mitochondrial dysfunction.
314 citations
TL;DR: In this paper, the authors discuss the background behind the huge interest in the important class of silica-coated magnetic nanoparticles (SMNPs) as nanocatalysts.
270 citations