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Hydrogen Peroxide Catalyzed (hydrogen + peroxide_catalyze)

Distribution by Scientific Domains
Chemistry100%
Distribution within Chemistry
Organic Chemistry66%
General & Introductory Chemistry33%

Selected Abstracts

Oxidation of ,4 - and ,5 -Steroids with Hydrogen Peroxide Catalyzed by Porphyrin Complexes of MnIII and FeIII

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2004
Susana L. H. Rebelo
Abstract In this paper we describe a new environmentally friendly method to promote the stereoselective epoxidation of ,4 - and ,5 -steroids. Metalloporphyrins efficiently catalyze the epoxidation reactions of 17,-acetoxy-4-androstene (1), 4-cholestene (2) and 3,-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 ,- or ,-epoxides. Porphyrins with bulky, electron-withdrawing groups in the ortho positions of the meso phenyls and with MnIII as the central metal ion, such as [Mn(TDCPP)Cl], gave preferentially the ,-epoxide of ,4 - and ,5 -steroids. [Fe(TPFPP)Cl] catalyzes preferentially the ,-epoxidation of ,4 -steroids and also increases the stereoselectivity for the ,-epoxide in ,5 -steroids, similar to the results obtained with m -CPBA (m -chloroperbenzoic acid) as oxidant. The substrate structure strongly influences the chemoselectivity of the reactions. The X-ray structures of two main products were determined, and two-dimensional NMR techniques allowed the full assignment of 1H and 13C NMR resonances as well as the stereochemistry of these products. A mechanistic proposal involving oxo species for the ,-approach and peroxy species for the ,-approach is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Highly Selective Oxidation of Organosilanes to Silanols with Hydrogen Peroxide Catalyzed by a Lacunary Polyoxotungstate,

ANGEWANDTE CHEMIE, Issue 47 2009
Ryo Ishimoto
Silanolsynthese: Das lakunare Polyoxowolframat (nBu4N+)4[,-SiW10O34(H2O)2] (I) mit zwei Leerstellen ist ein effizienter Homogenkatalysator für die hoch selektive Oxidation von Organosilanen zu Silanolen mit 30,60,% H2O2. Silane 1 mit Aryl-, Alkyl-, Alkenyl-, Alkinyl- und Alkoxygruppen werden in hohen Ausbeuten chemoselektiv zu den jeweiligen Silanolen 2 umgesetzt, wobei nur ein Äquivalent an wässrigem H2O2 in Bezug auf das Substrat benötigt wird. [source]

ChemInform Abstract: Selective and Mild Oxidation of Thiols to Sulfonic Acids by Hydrogen Peroxide Catalyzed by Methyltrioxorhenium.

CHEMINFORM, Issue 35 2008
Francesco P. Ballistreri
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Baeyer,Villiger Oxidation of Ketones with Hydrogen Peroxide Catalyzed by Sn,Aniline Complex.

CHEMINFORM, Issue 17 2008
Qing Hua Zhang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Enantioselective Oxidation of Sulfides with Hydrogen Peroxide Catalyzed by Vanadium Complex of Sterically Hindered Chiral Schiff Bases.

CHEMINFORM, Issue 13 2005
Yong-Chul Jeong
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Olefin Epoxidation with Hydrogen Peroxide Catalyzed by Lacunary Polyoxometalate [,-SiW10O34(H2O)2]4,

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2007
Keigo Kamata
Abstract The tetra- n -butylammonium (TBA) salt of the divacant Keggin-type polyoxometalate [TBA]4[,-SiW10O34(H2O)2] (I) catalyzes the oxygen-transfer reactions of olefins, allylic alcohols, and sulfides with 30,% aqueous hydrogen peroxide. The negative Hammett ,+ (,0.99) for the competitive oxidation of p -substituted styrenes and the low value of (nucleophilic oxidation)/(total oxidation), XSO=0.04, for I -catalyzed oxidation of thianthrene 5-oxide (SSO) reveals that a strongly electrophilic oxidant species is formed on I. The preferential formation of trans -epoxide during epoxidation of 3-methyl-1-cyclohexene demonstrates the steric constraints of the active site of I. The I -catalyzed epoxidation proceeds with an induction period that disappears upon treatment of I with hydrogen peroxide. 29Si and 183W,NMR spectroscopy and CSI mass spectrometry show that reaction of I with excess hydrogen peroxide leads to fast formation of a diperoxo species, [TBA]4[,-SiW10O32(O2)2] (II), with retention of a ,-Keggin type structure. Whereas the isolated compound II is inactive for stoichiometric epoxidation of cyclooctene, epoxidation with II does proceed in the presence of hydrogen peroxide. The reaction of II with hydrogen peroxide would form a reactive species (III), and this step corresponds to the induction period observed in the catalytic epoxidation. The steric and electronic characters of III are the same as those for the catalytic epoxidation by I. Kinetic, spectroscopic, and mechanistic investigations show that the present epoxidation proceeds via III. [source]