4- Bromophenyl methyl sulfide, oxidation

The (peroxo)di-iron(III) species (38b) and (38b ) " effect enantioselective sulfoxidation of aryl sulfides. In the catalytic reaction with FI2O2 as a terminal oxidant, saturation kinetics were observed with respect to both [FI2O2] and [sulfide]. The peroxo species (38b) + (38b ) generated in situ at 0°C decays in the presence of sulfide, following a saturation kinetics with respect to [sulfide]. For p-bromophenyl methyl sulfide, the ee approaches ca. 40%, providing compelling evidence for a metal-based oxidation pathway involving a (peroxo)di-iron(III)-sulfide binary complex embedded within chiral environment. 

The catalytic efficiency and selectivity of the Fe(II) complexes with three ligands (31) (R = O, OMe and C02Et) in the oxidation of a series of alkyls and alkenyls as well as the S atom of 4-bromophenyl methyl sulfide by H2O2 in the presence of AcOH has been compared with the catalytic efficiency of White s complex (32) in order to evaluate the sensitivity of the reaction to electronic effects. ... 

Another method, described by Jacobsen et al. [108], involves oxidizing the sulfide in the presence of an opticEilly active Salen manganese(III) chloride complex (49). Alkyl aryl sulfides were oxidized at room temperature in 1 h with 2 mol% of catalyst using hydrogen peroxide as the stoichiometric oxidant. Sulfoxide yields are generally high (8A-95%), with minimal overoxidation to sulfone. However, enantioselectivities are only moderate 34% and 68% for 2-methoxyphenyl methyl sulfoxide and 2-bromophenyl methyl sulfoxide, respectively (Table 1.5). 

Chiral (salen)Mn(III)Cl complexes are useful catalysts for the asymmetric epoxidation of isolated bonds. Jacobsen et al. used these catalysts for the asymmetric oxidation of aryl alkyl sulfides with unbuffered 30% hydrogen peroxide in acetonitrile [74]. The catalytic activity of these complexes was high (2-3 mol %), but the maximum enantioselectivity achieved was rather modest (68% ee for methyl o-bromophenyl sulfoxide). The chiral salen ligands used for the catalysts were based on 23 (Scheme 6C.9) bearing substituents at the ortho and meta positions of the phenol moiety. Because the structures of these ligands can easily be modified, substantia] improvements may well be made by changing the steric and electronic properties of the substituents. Katsuki et al. reported that cationic chiral (salen)Mn(III) complexes 24 and 25 were excellent catalysts (1 mol %) for the oxidation of sulfides with iodosylbenzene, which achieved excellent enantioselectivity [75,76]. The best result in this catalyst system was given by complex 24 in the formation of orthonitrophenyl methyl sulfoxide that was isolated in 94% yield and 94% ee [76]. 

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See also in sourсe #XX -- [ ]

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