Peroxides, oxidation with

Sheldon, R. Homogeneous and Heterogeneous Catalytic Oxidations with Peroxide Reagents. 164, 21-43 (1993). 

Moreover, the membrane could be mounted as an interface between the apolar substrate and the polar oxidant in a membrane reactor, avoiding the use of any solvent. Dilution of the reagents by solvent and competition between solvent and reagents on the active sites can thus be avoided. In the countercurrent membrane reactor, the substrate and the oxidant are circulated at each side of the membrane and alkanes can be oxidized with peroxides without solvents. Of course, the system carries all of the other advantages of membrane reactors continuous operation and easy separation. 

The accepted mechanistic scheme for metal catalyzed oxidations with peroxides is sketched in Scheme 1. The features of the active oxidant depend on the nature of the oxygen donor and on its interaction with the metal precursor in several examples high-valent peroxo metal species have been recognized as competent intermediates ... 

In the earlier volume of this book, the chapter dedicated to transition metal peroxides, written by Mimoun , gave a detailed description of the features of the identified peroxo species and a survey of their reactivity toward hydrocarbons. Here we begin from the point where Mimoun ended, thus we shall analyze the achievements made in the field in the last 20 years. In the first part of our chapter we shall review the newest species identified and characterized as an example we shall discuss in detail an important breakthrough, made more than ten years ago by Herrmann and coworkers who identified mono- and di-peroxo derivatives of methyl-trioxorhenium. With this catalyst, as we shall see in detail later on in the chapter, several remarkable oxidative processes have been developed. Attention will be paid to peroxy and hydroperoxide derivatives, very nnconunon species in 1982. Interesting aspects of the speciation of peroxo and peroxy complexes in solntion, made with the aid of spectroscopic and spectrometric techniqnes, will be also considered. The mechanistic aspects of the metal catalyzed oxidations with peroxides will be only shortly reviewed, with particular attention to some achievements obtained mainly with theoretical calculations. Indeed, for quite a long time there was an active debate in the literature regarding the possible mechanisms operating in particular with nucleophilic substrates. This central theme has been already very well described and discussed, so interested readers are referred to published reviews and book chapters . 

The second part of the chapter will be dedicated to the reactivity of transition metal peroxides, either isolated or formed in solution in catalytic processes, toward several classes of substrates. Hopefully this survey, where particular emphasis is placed on the selectivity aspects of these reactions, will present to the readers the potential of metal catalyzed oxidations with peroxides and highlight the perspective for researchers in the field. 

Vanadium-catalyzed hydrocarbon oxidation with peroxides can be carried out also by supporting the catalyst with the appropriate ligand on polymers " , on sUica " or encapsulating it in zeolites ". Similar activity has been obtained with vanadium-containing... 

With this chapter we hope that newcomers to the field have received a taste of how active is the research in metal-catalyzed oxidation with peroxides, and also in fntnre perspectives of greener and more efficient oxidative protocols. Additionally, we hope that people deeply involved in this area will appreciate the collection of the main literatnre that has been published in these last 20 years. 

D Oxidation with Peroxidic Compounds. Oxacyclopropane (Oxirane) Formation... 

Boron-mediated ketone-ketone aldol reactions have been described, using boron enolates formed with dicyclohexylboron chloride and triethylamine.124 Following addition of the acceptor ketone to form a boron aldolate, oxidation with peroxide yields the aldol product. 

Sulfur compounds I, II and IV, methyl sulfonic acid, ethylsulfonic acid and benzenesulfonic acid could have been derived from a number of precursors in the parent coal samples. Firstly, mercaptans and thiols will form sulfonic acids when oxidized with peroxides. However, the presence of methylmercaptan, ethylmercaptan and benzenethiol in an exhaustively extracted coal sample is highly unlikely and we believe that the sulfonic acids did not arise from these compounds. In addition, there is a possibility that these sulfonic acids may have come from pendant or terminal thioether groups. 

Oxidation with Peroxides, Especially Perbenzoic Acid. 219... 

ESI and APCI. LC/MS is considerably improved after precolumn oxidation with peroxide to the pentavalent acids (27) and (29). These can be chromatographed on a polymeric PRP-1 column using a standard water-CH3CN-0.2 % formic acid gradient (69). 

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