Hydroxylation, alkene aromatic

In the same spirit DFT studies on peroxo-complexes in titanosilicalite-1 catalyst were performed [3]. This topic was selected since Ti-containing porous silicates exhibited excellent catalytic activities in the oxidation of various organic compounds in the presence of hydrogen peroxide under mild conditions. Catalytic reactions include epoxidation of alkenes, oxidation of alkanes, alcohols, amines, hydroxylation of aromatics, and ammoximation of ketones. The studies comprised detailed analysis of the activated adsorption of hydrogen peroxide with... 

The reaction is carried out using a titanium silicalite-1 (TS-1) zeolite catalyst [30, 122]. This type of catalyst is known to accelerate the selective oxidation of alcohols, epoxidation of alkenes and hydroxylation of aromatics. These reactions have importance for fine-chemical production. 

Co(ni) alkyl peroxides have been prepared and used by Mimoun and coworkers in the hydroxylation of hydrocarbons with this metal a Haber-Weiss type of reactivity is suggested. Square-planar Pt(II) complexes, of the type [(dppe)Pt(CF3)(solv)], used by Strukul in the epoxidation of alkenes and in Baeyer-Villiger oxidations of ketones (Schemes 8 and 9), are effective catalysts also in the direct hydroxylation of aromatics with hydrogen peroxide. The reactivity increases in the presence of electron releasing substituents in the aromatic ring. Ortho and para derivatives are practically the only products observed and interesting selectivity toward the ortho products has been detected (equation 85). 

Aromatic hydroxylation/alkene epoxidation Titanium silicate Styrene to phenylacetaldehyde, ethylene to ethylene oxide and other reactions... 

Addition has also been shown to occur when the pyridinlum iodide (139) is irradiated. The product Is assigned the structure (140) and the relevance of this reaction to the photoreactivity of Kosower solvent polarity probes has been discussed. The use of osmium tetroxide to hydroxylate alkenes is a well known procedure which is often carried out in aromatic solvents. These arene solvents form charge transfer complexes with the osmium tetroxide and the photochemistry of these has now been examined. It is shown that with benzene and alkyl benzenes isolable adducts are formed that from benzene Is assigned structure (141). 

Whereas important progress has been made regarding the use of metalloporphyrins as catalysts for alkene epoxidations and alkane hydroxyla-tions, work concerning the mechanism of hydroxylation of aromatic hydrocarbons has received only limited attention. In fact, the main problem encountered with the design of systems capable of performing such oxidative reactions is in the preparation of superstructured porphyrins for the selective complexation of aromatic compounds. 

S. Banfi, M. Cavazzini, G. Pozzi, S. V. Barkanova, O. L. Kaliya, Kinetic studies on the interactions of manganese-porph)Tins with peracetic acid. Part 1. Epoxidation of alkenes and hydroxylation of aromatic rings, J. Chem. Soc. Perkin Trans. 2(4) (2000) 871. 

Oxidations/hydroxylations of linactivated saturated carbons (polyunsaturated) fatty acids epoxidation and dihydroxylation of alkenes aromatic compounds (- unsaturated diols) hydroxylated compounds and aldehydes diols (and lactonization) enzyme catalyzed Baeyer-Villiger oxidations organic sulfides (sulfoxidation) Be, Mi, Mp, Po, Ra, CytP450 enzymes, monooxygenases SLO An, Nc, Po Pp (mutant strain), Ce Go, Ps Bp, Go, Ko, Ps, HLADH Ac, Ps, CHO BY, An, Ceq, Mi, Po, CPO, BSA... 

Hydrogen peroxide in combination with catalysts such as TS-1 acts as a good, "clean" epoxidation system. T e reactions that could be carried with this catalyst include ammoximation of cyclohexanone, epoxidation of propene and other small alkenes, and hydroxylation of aromatics and linear alkanes (Chapter 4). The system produces little waste, avoids the use of hazardous chemicals such as alkyl hydroperoxide, and reduces process complexity. However, the key parameter for industrial development is the cost of H2O2. H2O2 is produced by only a few companies, and very large capital expenditure is required, because H2O2 synthesis (by alkyl-anthraquinone route) is economical only when large quantities are produced. 

There are two directions in the development of supramolecular catalytic compositions, that is, (1) creation of systans based on macrocyclic compounds as host molecules that bind substrates with their hydrophobic cavity and (2) development of the systems that bind substrates using aggregates formed by am-phiphihc compounds. Compounds that form host-guest complexes like modified cahxarenes are able to aid transport of substrates into the aqueous phase. This approach has been implemented in the Wacker oxidation [40,41], oxidation of alkylaromatic compounds [42], hydroxylation of aromatic compounds [43], hydrogenation [44,45], hydroformylation [45-48], and carbonylation [49]. In this case, the substrate is transported into the aqueous phase in the form of the corresponding inclusion complex. This not only affects the activity of the catalyst, but also provides selectivity of the process. Thus, in the Wacker oxidation of 1-alkenes the maximum yield of methyl ketone was achieved when 1-hexene is used, and for systems based on calix[6]arene with 1-octene among catalytic systems with modified calix[4]arenes [50]. 

The P450s catalyze a variety of reactions, including hydroxylation, epoxidation, peroxidation, sulfoxidation, dealkylation, deamination, etc., depending on the substrate structures. Many substrates, including alkenes, aromatic hydrocarbons, heterocycles, vinyl halides, e yl carbamate, vinyl nitrosamines, and aflatoxin Bl, have been epoxi-dized with good stereoselectivities by the membrane-boimd mammalian P450s [29]. 

A chlorohydrin has been defined (1) as a compound containing both chloio and hydroxyl radicals, and chlorohydrins have been described as compounds having the chloro and the hydroxyl groups on adjacent carbon atoms (2). Common usage of the term appHes to aUphatic compounds and does not include aromatic compounds. Chlorohydrins are most easily prepared by the reaction of an alkene with chlorine and water, though other methods of preparation ate possible. The principal use of chlorohydrins has been as intermediates in the production of various oxitane compounds through dehydrochlorination. 

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