Hydroperoxide groups from phenyl group

The stereospecific labeling of the anti methyl by deuterium in compound 20 to produce substrate 21 (Table 3) was required in order to study the syn/anti regioselectivity of the ene allylic hydroperoxides. The ene products in different solvents showed a preference for hydrogen abstraction from the methyl syn to the phenyl group. The magnitude of this selectivity depends on solvent polarity. On increasing the solvent polarity, a substantial increase in the amount of syn product occurs (Table 3). 

Two different cases may occur. If this radical is formed in a succession of styrene units (1), it reacts in the same way as in PS. If it is formed on a styrene unit linked to an acrylonitrile unit (2), three reaction pathways may be envisaged. The alkoxy radical resulting from the decomposition of the hydroperoxide formed on this polystyryl radical may react by 3-scission. Scissions (a) and (b) yield chain ketones, acetophenone end-groups and phenyl and alkyl radicals as previously observed in the case of PS photooxidation mechanism. Scission (c) leads to the formation of an aromatic ketone and an alkyl radical. This alkyl radical may be the precursor of acrylonitrile units (identified by IR spectroscopy at 2220 cm-1), or may react directly with oxygen and after several reactions generates acid groups, or finally this radical may isomerize to a more... 

MisceUaneous.—The carbanions (94), formed from the reaction of the corresponding phosphonium salt with sodium ethoxide and the sodium salt of t-butyl hydroperoxide, decompose in a number of ways. Migration of a phenyl group to oxygen yields the phosphine oxide (95) and formation of the alkyl ethyl ethers may be due to the intermediacy of a carbene, which is trapped by solvent. ... 

The positions of hydroperoxy groups formed during the oxidative deterioration or degradation of lipids are most commonly determined by reduction of the hydroperoxide to a hydroxyl group and hydrogenation of any double bonds, followed by methylation and conversion to the TMS ether derivative for GC-MS. This approach is also of value with the eicosanoids derived from arachidonic acid. Those papers cited here are representative of many [223,263,604,833, 879,911,984,1005]. Similar results are obtained with phenyl esters [371]. 

ENERGY TRANSFER FROM THE PHENYL GROUP TO THE HYDROPEROXIDE GROUP... 

Energy transfer from the excited phenyl group (donor) to the surrounding hydroperoxide groups (acceptors) may occur in many polymers and copolymers containing phenyl groups. 

Phenyl rings absorb incident light at 254 nm and transfer the energy of the excited singlet state to hydroperoxide groups and cause the O—O band dissociation [287, 293]. However, the energy transfer may also occur, to a lesser extent, from the excimer [282]. 

Formation of hydroperoxide groups causes quenching of the fluorescence emission from excited phenyl groups in rubbers containing phenyl groups... 

A further catalytic method for asymmetric sulfoxidation of aryl alkyl sulfides was reported by Adam s group, who utilized secondary hydroperoxides 16a, 161 and 191b as oxidants and asymmetric inductors (Scheme 114) . This titanium-catalyzed oxidation reaction by (S)-l-phenylethyl hydroperoxide 16a at —20°C in CCI4 afforded good to high enantiomeric excesses for methyl phenyl and p-tolyl alkyl sulfides ee up to 80%). Detailed mechanistic studies showed that the enantioselectivity of the sulfide oxidation results from a combination of a rather low asymmetric induction in the sulfoxidation ee <20%) followed by a kinetic resolution of the sulfoxide by further oxidation to the sulfone... 

Catalytic oxidations of sulfides were carried out in 1,2-dichloroethane with cumyl hydroperoxide by using 10 mol % of the catalyst. The best enantioselectivity was achieved with complex 6c. However, sulfone was always produced as byproduct of the reaction. Even with a limited amount of hydroperoxide, the sulfone formation could not be avoided. For example, the reaction of methyl p-tolyl sulfide using 0.5 mol equiv. of cumyl hydroperoxide with respect to sulfide gave a 62 38 mixture of the corresponding (.S j-sulfoxide and sulfone. The reaction of benzyl phenyl sulfide led to the formation of (5)-sulfoxide (84% ee) and sulfone ([sulfox-ide]/[sulfone] = 77 23). It was established that sulfone was produced from the early stages of the reaction. It was also demonstrated that some kinetic resolution of the sulfoxide cooperated with the enantioselective oxidation of the sulfide. A unique feature of this oxidation system, as compared to those using various Ti(IV)/(DET) complexes, is the insensitivity of the enantioselectivity (40-60% ee at 0°C) to the nature of the alkyl group of sulfides Ar-S-alkyl. 

Allyl phenyl telluriums, prepared from allyl halides and benzenetellurolate, experience oxidative cleavage of the allyl group when treated with hydrogen peroxide, tcrr.-butyl hydroperoxide, sodium periodate, oxygen, or air The allyl group is converted to unsaturated alcohols, aldehydes, and ketones. Before elimination from the molecule the phenyltelluro group is probably oxidized to a telluroxide or a tellurinic ester ... 

The above conditions are not suitable for p-hydroxyalkyl methyl selenides (Scheme 175, a) or for 3-hydroxyalkyl phenyl selenides bearing a primary hythoxy group (Scheme 176, a). Several other conditions including ozone and r-butyl hydroperoxide are not efficient for that purpose (Schemes 175 and 176). The best reagent is r-butyl hydroperoxide supported on basic alumina. The reaction takes place at reflux in THF, and allows the synthesis from -hydroxyalkyl methyl selenides of a large variety... 

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