Monooxygenated intermediate

The degradation of acenaphthene is initiated by benzylic monooxygenation, and the pathway was determined using [l- C]acenaphthene by the isolation of intermediate metabolites (Selifonov et al. 1998). Importantly, the method proved applicable even when only limited biotransformation of the substrates had taken place by partial oxidation. 

The degradation of 2,4,6-trichlorophenol has been examined in a number of bacteria. Monooxygenation plays a key role, and 2,6-dichlorobenzoquinone and 6-chlorohydroxy-quinol have been recognized as intermediates ... 

Epoxides, also known to chemists as oxiranes, result from the monooxygenation of a C=C bond in olefins or aromatic rings. Such reactions of monooxygenation to produce epoxides as metabolites or metabolic intermediates... 

Reduced flavins, unlike reduced nicotinamides, are reactive towards molecular oxygen, and an intermediate produced in this reaction is a more potent oxygenating agent than molecular oxygen is itself. A number of enzymes have evolved which utilize this intermediate to oxygenate certain metabolites. These reactions usually entail monooxygenation (Scheme 5). There are, however, at least two examples of dioxygenation that have been reported... 

Phase I monooxygenations are more likely to form reactive intermediates than phase II metabolism because the products are usually potent electrophiles capable of reacting with nucleophilic substituents on macromolecules, unless detoxified by some subsequent reaction. In the following discussion, examples of both detoxication and intoxication reactions are given, although greater emphasis on activation products is provided in Chapter 8. 

Hydroperoxo-ferric complex in heme oxygenase reserves a special place among other heme enzymes being the main catalytically active intermediate on the first monooxygenation step of HO catalysis. Conversion of heme to biliverdin, catalyzed by HO, begins with reduction of the ferric heme iron, binding of dioxygen, and second reduction... 

Intermediate formation mechanisms indicated in the monooxygenation diagram relate to the class of reactions in non-aqueous solvents. This is the reason why the hemin form of iron porphyrin is absent in it. Hence, hemin is present, of which the intermediate formation shaped as Hm+0 (where Hm is heme) is typical. 

According to data in the literature [1], catalytic monooxygenation of propylene with hydrogen peroxide in the presence of perFTPhPFe(III)0H/Al203 has an intermediate, shaped... 

Shteinman, A.A. (2001) The role of metal-oxygen intermediates in biological and chemical monooxygenation of alkanes, Russian Chemical Bulletin 50, 1795-1810. 

In the past 25 years, Fe =0 and Mn =0 have also emerged as reactive intermediates in the oxidation of hydrocarbons they are not formed by interaction with dioxygen but rather by monooxygen donors (see below). 

Over the past 25 years, biomimetic model systems have been extensively studied and a wide variety of interesting oxidation processes such as the epoxidation of olefins, the hydroxylation of aromatics and alkanes, the oxidation of alcohols to ketones, etc., have been accomplished some of these are also known in enantioselective versions with spectacular ee s. The vast majority of these transformations were obtained using monooxygen donors such as those mentioned above as primary oxidants. The complexity of the catalysts and the practical impossibility to use dioxygen as the terminal oxidant have so far prevented the use of such systems for large industrial applications, but some small applications in the synthesis of chiral intermediates for pharmaceuticals and agrochemicals, are finding their way to market. 

In a base-free medium (dry MeCN), Fe Ch activates HOOH to form a reactive intermediate that oxygenates alkanes, alkenes, and thioethers, and dehydrogenates alcohols and aldehydes. Table 11 summarizes the conversion efficiencies and product distributions for a series of alkene substrates subjected to the Fe Cfi/HOOH/MeCN system. The extent of the Fe Cb-induced monooxygenations is enhanced by higher reaction temperatures and increased concentrations of the reactants (substrate, Fe Cls, and HOOH). For 1-hexene (representative of all of the alkenes), a substantial fraction of the product is the dimer of 1-hexene oxide, a disubstituted dioxane. With other organic substrates (RH), Fe Cb activates HOOH for their monooxygenation the reaction efficiencies and product distributions are summarized in Tables 11(b). In the case of alcohols, ethers, and cyclohexane, a snbstantial fraction of the product is the alkyl chloride, and with aldehydes, for example, PhCHO, the acid chloride represents one-half of the product. In the absence of snbstrate the Fe Cls/MeCN system catalyzes the rapid disproportionation of HOOH to O2 and H2O. 

This C(4a)-hydroperoxyflavin intermediate is the active form of the cofactor in a monooxygenation reaction, leading to the hydroxylation of aromatic substrates. The reaction mechanism is schematically depicted in Fig. 4.81. Table 4.3... 

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