Oxidative transformations

The chelated complex of the benzylamine derivative 505 underwent a remarkable oxidative transformation by treatment with thallium trifluoroace-tate to give narwedine (506) in one step by biomimetic oxidation[459]. 

Nitration. Because nitration frequentiy generates nitrogen oxides which can participate in oxidative transformations, the nitration of indole itself is a complex reaction. In strongly acidic media, the nitration of 2-substituted indoles can proceed through the conjugate acid (8). Because the aromatic system is thereby transformed to an a2astyrene, the 5-position is the primary site of reaction. 

Scheme 9 Oxidative transformation products formed during the antioxidant action of BHT.

In all cases except Li3Nb04, phases similar to Li4Nb04F and Li4Ta04F were found. Pure binary oxides transform easily to modified structures characterized by ordered cation distribution, while oxyfluorides are more stable and require treatment at a high temperature, for an extended period of time, in order to be transformed into a state of ordered cation distribution. 

PO performs vitally important functions in the plant cell and is mainly associated with the oxidation of phenolic compounds and with the formation and strengthening of the cell wall (Passardi et al., 2004). PO is involved in the oxidative transformation of molecules in growth-regulating or signalling activities and - as a result - can also perform regulatory functions in the cell. Plant POs are represented by genetically different proteins with the same enzymatic activity (Welinder et al., 2002). 

Remarkably, alkanes are oxidatively transformed by biological organisms at benign temperatures and pressures. Clearly, enzymatic transformations of alkanes and their well studied mechanisms (e.g., for cytochrome P450) are beyond the... 

Zhang H, C-H Huang (2003) Oxidative transformation of triclosan and chlorophene by manganese dioxides. Environ Sci Technol 37 2421-2430. 

Johnson GR, BF Smets, JC Spain (2001) Oxidative transformation of aminodinitrotoluene isomers by multi-component dioxygenases. Appl Environ Microbiol 67 5460-5466. 

The Oxidative Transformation of Methane over the Nickel-based Catalysts Modified by Alkali Metal Oxide and Rare Earth Metal Oxide... 

The large amounts of natural gas (mainly methane) found worldwide have led to extentive research programs in the area of the direct conversion of methane [1-3]. Ihe oxidative transformation of methane (OTM) is an important route for the effective utilization of the abundant natural gas resources. How to increase catalyst activity is a common problem on the activation of methane. The oxidation of methane over transition m al oxides is always high active, but its main product is CO2, namely the product of deep oxidation. It is because transition metal oxides have high oxidative activity. So, they were usually used as the main corrqtonent of catalysts for the conqilete oxidation of alkane[4]. The strong oxidative activity of CH4 over tran on metal oxides such as NiO indicates that the activation of C-H bond over transition metal oxides is much easier than that over alkaline earth metal oxides and rare earth metal oxides. Furthermore, the activation of C-H bond is the key step of OTM reaction. It is the reason that we use transition metal oxides as the mam conq>onent of the OTM catalysts. However, we have to reahze that the selectivity of OTM over transition metal oxides is poor. 

We expected to control the direction of OTM reaction over NiO by sur ce modification, namely making use of the interaction between NiO and other conq>onents to beget a synergistic effect. In this paper, two completely different behaviors of the oxidative transformation of methane were performed over the nickel-based catalysts because of the different modifications by alkali metal oxide and rare earth metal oxide and the different interactions between nickel and supports. Furthermore, the two completely different reactions were related with the acid-base properties of catalysts and the states of nickel present. 

Two conqiletely different behaviors of oxidative transformation of methane, namely the Oxidative Coupling of Methane to C2 Hydrocarbons(OCM) and the Partial Oxidation of Methane to Syngas(POM), were performed and related over the nickel-based catalysts due to different modification and different supports. It is concluded that the acidic property favors keeping the reduced nickel and the reduced nickel is necessary for POM reaction, and the bade property frvors keeping the oxidized nickel and the oxidized mckel is necessary for OCM reaction. POM and OCM reactions proceed at different active sites caused by different... 

Bismuth sesquioxide, BijOj, exhibits a high oxide ion conductivity at high temperature without doping of aliovalent cations. The oxide transforms from the monoclinic... 

This article mostly focuses on the catalytic pinacol coupling and related reductive transformations via one-electron transfer. On the other hand, the corresponding methods for catalytic oxidative transformations via one-electron oxidation have been scarcely investigated and remain to be developed. Both methods are complementary and useful for generating radical intermediates. 

A very mild oxidative transformation of nitro compounds into ketones using tetrapropylam-monium perruthenate (TPAP) has been developed. A stoichiometric amount of TPAP in the presence of A-methylmorpholine A-oxide (NMO) and 4 A molecular sieves (MS).18a As the reaction conditions are neutral and mild, this method is compatible with the presence of other sensitive functionalities (Eq. 6.11). This transformation can be carried out with 10 mol% of TPAP and 1.5 equiv of NMO in the presence of potassium carbonate, 4 A MS, and silver acetate (Eq. 6.12).18b... 

Interestingly, okadaic acid diol ester (16) in the culture medium is oxidatively transformed into the more hydrophilic metabolites 18-20 by intact cells of the diatom Thalassiosira weissflogii [52,53]. This transformation is speculated to change the toxic metabolite with allelopathic activity into a less toxic transport form that can be better excreted by the diatom. 

Scheme 5 Release of okadaic acid (17) from less toxic precursors by E. lima (left). Oxidative transformation of okadaic acid diol ester (16) by the diatom Thalassiosira weissflogii (right)...

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