Aryl benzyl sulfide, oxidation

A chiral Ti complex formed in situ by reacting Ti(0 Pr)4, (J ,P)-diphenylethane-1,2-diol, and water was reported to be effective for asymmetric oxidation of aryl alkyl and aryl benzyl sulfides using TBHP as the oxidant to obtain optically active sulfoxides in good yields and high enantiomeric excesses [274] (Scheme 14.115). 

Steric and electronic effects have been investigated for the Cu(acac)2-catalysed asymmetric oxidation of aryl benzyl, aryl alkyl and alkyl benzyl sulfides with H2O2 in presence of hexane/MeOH and the ligand 4-chloro-2-[( )-[( 17 )-l-(hydroxymethyl)-2,2-dimethyl-propyl]iminomethyl]phenol. High enantioselectivity is dependent on the attachment of an aryl group to the sulfur and was highest, with up to 97% ee, for 2-naphthyl benzyl sulfoxide. Cu-mediated oxidation of substituted aryl benzyl sulfides shows modest steric and electronic effects. ... 

The complex (70) is the most efficient catalyst in the titaniumsalan-catalysed asymmetric oxidations of bulky aryl benzyl sulfides and small alkyl phenyl sulfides by H2O2 in CH2CI2 to corresponding sulfoxides with 77% ee. The kinetics suggest that a direct attack of the sulfide on the electrophilic active oxygen species occurs... 

A new catalytic procedure for the asymmetric oxidation of aryl alkyl and aryl benzyl sulfides to optically active sulfoxides by TBHP is mediated by a chiral titanium complex formed in situ by reacting Ti( -PrO)4, (R, / )-diphenylethane-l,2-diol, and water. The results were largely unaffected by the nature of the phenyl substituents, suggesting that the same mechanism operates in all cases. Only the / -N02 substituent on the aryl ring caused a considerable loss of enantioselectivity and this is attributed to the electron-withdrawing power of this group or, more likely, its coordinating ability. ... 

The reaction described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons.2"8 Reactions of 2-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons,9, 10 esters,6,11 dialkyl and aryl alkyl ethers,12 14 benzylic ethers,11,15 cyclic ethers,13,16 straight-chain and benzylic sulfides,12, 17-19 cyclic sulfides,11,19 amides,11 and certain organo-silicon compounds.20... 

The oxidation of sulfides to sulfoxides is a key routine organic transformation. Oakes et al. have developed conditions to enable this reaction to be carried out in supercritical carbon dioxide, with clean sulfoxide formation and no overoxidation to the sulfone (1999). Using TBHP as the oxidant and Amberlyst 15 as a heterogeneous acid catalyst, a range of alkyl, aryl, and benzyl sulfides have been selectively oxidized to the sulfoxide in quantitative yield. 

A mild and chemoselective oxidation of sulfides to sulfoxides by o-iodooxybenzoic acid (IBX) catalyzed by tetraethylammonium bromide (TEAB) has been reported [73]. The reaction is highly selective, and no overoxidation to sulfone was observed. Simple aryl alkyl sulfides are oxidized in 93-98% yield in 0.3-2 h at room temperature with the use of 5 mol% of TEAB. Diphenyl sulfide and phenyl benzyl sulfide took 30 and 36 h, respectively, to go to completion under these conditions. 

Phenyl methyl and benzyl sulfides have been catalytically oxidized to corresponding sulfoxides (>80%) and sulfones (<10%) using lutidine N-oxide as oxidant in the presence of Ru(TMP)(0)2 the reaction takes days at ambient conditions, and depends especially on the coordination ability of the sulfide and sulfoxide . Considering the non-reactivity of aryl sulfides toward the dioxo species, the amine oxide may well play a role as an axial ligand in these systems (see Sections 3.3 and 3.4). 

Nucleophilic reactivity of exocyclic sulfur appears in acidic medium. 2-Aryl thiazolyl sulfones are obtained from the corresponding sulfides by oxidation with H2Oz in HOAc at 100°C (272). The same oxidation takes place with alkyl sulfides (203. 214, 273-275) and dithiazolylsulfides (129). However, the same reaction with 2-benzylthio derivatives gives benzylal-cohol and the related A-4-thiazoline-2-thione (169). 

This I04 -5i02 reagent is not very elective in the oxidation of sulfides into sulfoxides. However, sulfuryl chloride adsorbed wet silica gel is an excellent reagent for this transformatim (equation 5). High yields of methyl aryl, diaryl, allylic. benzylic and dialkyl sulfoxides are thus obtainable. The procedure commends itself by its simplicity and its extension to thioacetals provides a good, quantitative re-... 

The products of the electrochemical oxidation of alkyl aryl sulfides, ArSR, are remarkably dependent upon the structure of R, the water content of the solvent, and the supporting electrolyte. If R can yield stabilized carbocations like benzyl or triphenyl-methyl cations, extensive cleavage of the S-C bond occurs during the oxidation [84, 85] ... 

Hart assembled olefin 109 convergently from benzyl bromide 106 by taking advantage of the Ramberg-Backlund reaction.59 As depicted below, the Sn2 displacement of benzyl bromide 106 with thiol 107 led to sulfide 108. Oxidation of 108 to the sulfone, followed by the Myers modification delivered alkene 109, an intermediate for the synthesis of C-aryl glycosides related to chrysomycins. 

Additives used in finai products Fillers aluminum oxide, calcium carbonate, clay, carbon black, ferrite, graphite, magnesium oxide, nanocellulose, sand, silica, titanium dioxide, zinc oxide, zirconia Plasticizers benzyl butyl phthalate, dipropylene glycol dibenzoate, glycerin, monostea-ryl citrate, polyethylene and polypropylene glycols, triacetin Antistatics alkyl aryl sulfonate, cadmium sulfide, ethoxylated fatty acid amine, tetraammonium salt Antiblocking talc Release silane modified PVOH Slip PTFE beads Crosslinkers Defoamers ... 

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