Peroxides allylic oxidation

ALLYLIC OXIDATION WITH HYDROGEN PEROXIDE-SELENIUM DIOXIDE frans-PINOCARVEOL... 

When preparing allyl oxide according to this method, a violent detonation interrupted the operation. It was explained by the alcohol polymerisation catalysed by sulphuric acid. There was a less convincing explanation, which is peroxidation in the allylic position of alcohol or the ether obtained. Indeed, there should have been prolonged storage for this peroxidation. 

Allylic oxidation can be carried out using a peroxide together with a copper (I) complex. Enantioselective processes have now been developed using tertiary-butylperbenzoate and either copper (I) or copper (II) complexes in acetonitrile (Figure ll.ll). ... 

ALLYLIC OXIDATION r-Butyl hydro-peroxide-Selenium dioxide. Chromic anhydride. 

The known allylic alcohol 9 derived from protected dimethyl tartrate is exposed to Sharpless asymmetric epoxidation conditions with (-)-diethyl D-tartrate. The reaction yields exclusively the anti epoxide 10 in 77 % yield. In contrast to the above mentioned epoxidation of the ribose derived allylic alcohol, in this case epoxidation of 9 with MCPBA at 0 °C resulted in a 65 35 mixture of syn/anti diastereomers. The Sharpless epoxidation of primary and secondary allylic alcohols discovered in 1980 is a powerful reagent-controlled reaction.12 The use of titanium(IV) tetraisopropoxide as catalyst, tert-butylhydro-peroxide as oxidant, and an enantiopure dialkyl tartrate as chiral auxiliary accomplishes the epoxidation of allylic alcohols with excellent stereoselectivity. If the reaction is kept absolutely dry, catalytic amounts of the dialkyl tartrate(titanium)(IV) complex are sufficient. 

The absence of allylic oxidation products seems to point to the heterolytic ring opening of the peroxide as dominant pathway. The excellent properties of... 

Recently, iron catalysis gained general importance. Its catalytic chemistry has been summarized ([2] recent reviews [3, 4]). Iron(II) and iron(III) salts have a long history in radical chemistry. The former are moderately active in atom-transfer reactions as well as initiators for the Fenton reaction with hydrogen peroxide or hydroperoxides (reviews [5-12]). Important applications of this principle are the Kharasch-Sosnovsky reaction (the allylic oxidation of olefins) [13], which often... 

Thus, the isotope effect for the allylic oxidation of cyclohexene by cytochrome P 450 is about 5 and is the same for the reconstituted, NADPH-dependent and the peroxide-dependent paths. This similarity suggests that although product ratios may change from one oxygen donor to another, the mechanism of oxygen transfer may be invariant. Efforts to develop a clearer understanding of the relationships between the 02-dependent and peroxide-dependent pathways for oxygen transfer catalyzed by cytochrome P 450 are currently underway. 

Complex 29 catalyzes the disproportionation of hydrogen peroxide to oxygen and water (48). In the absence of readily oxidizable substrates, it degrades. In the presence of olefins, however, it catalyzes the formation of epoxides. This catalysis was demonstrated for cyclohexene (1.6 turnovers), styrene (3.2 turnovers), and ds-stilbene (2.5 turnovers). The formation of the epoxides is not exclusive, because allylic oxidation... 

Oxidation of alcohols. In the presence of catalytic amounts of pyridinium dichromate, this peroxide can oxidize primary and secondary alcohols to the corresponding carbonyl compounds in 70-100% yield. Reactions catalyzed by dichloro-tris(triphenylphosphinc)ruthenium are useful for highly selective oxidation of primary allylic and benzylic alcohols m the presence of secondary ones. 

Oxidations. A widely used method for allylic oxidation is the Kharash-Sosnovsky reaction using a peroxide and a copper(I) salt system. Enantioselective allylic oxidations of cycloalkenes such as cyclopentene, cyclohexene and cycloheptene with tert-butyl peibenzoate were investigated with a variety of catalysts derived from bis(oxazoline) ligands and copper(I) triflate complexes (eq 18). The ligand-copper(I) complexes from the /-Bu-... 

Next, some sort of allylic oxidation at the position between the alkene and the benzene ring. This would be with some oxygenation reagent such as FAD peroxide. The position is very reactive and would easily form radicals (Chapter 39). 

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