Dimethyl sulphoxide photolysis

The photolysis of dimethyl sulphoxide (at 253.7 nm) in a wide range of solvents has been studied in detail176. Three primary reactions occur, namely (i) fragmentation into methyl radicals and methanesulphinyl radicals, equation (60), (ii) disproportionation into dimethyl sulphone and dimethyl sulphide, equation (61) and (iii) deactivation of the excited state to ground state dimethyl sulphoxide. All chemical processes occur through the singlet state. Further chemical reactions of the initial photochemical products produce species that have been oxidized relative to dimethyl sulphoxide. 

Gollnick and Stracke176 investigated the very complex mechanism involved in the photolysis of dimethyl sulphoxide and concluded that disproportionation is probably the route for the major sulphone-producing reaction. Other oxidized species such as methanesulphonic acid are also produced and are also probably formed by a series of disproportionation reactions, for example equation (62). Thus photolysis of dimethyl sulphoxide is not a synthetically useful reaction due to the large number of compounds produced. 

Dihydrodithiin sulphoxides, synthesis of 243 Dihydrothiophene dioxides, reactions of 653 /(,/( -Dihydroxyketones 619 Dimerization, photochemical 877, 884 Dimethyl sulphoxide anion of - see Dimsyl anion hydrogen bonding with alcohols and phenols 546-552 oxidation of 981, 988 photolysis of 873, 874, 988 radiolysis of 890-909, 1054, 1055 self-association of 544-546 Dimsyl anion... 

Photolysis of sulphonyl azides in dimethyl sulphoxide with 2537 A light gives IV-sulphonylsulphoximines 12 in 15—50% yield 5>. The reaction was formulated as going via a nitrene intermediate which was trapped by the nucleophilic solvent... 

In contrast to the problems encountered on photolysis of alkyl- and aryl-sulphonyl azides, we have found that ferrocenylsulphonyl azide 74 is smoothly decomposed by 3500 A light in cyclohexane or in benzene to give ferrocene 15, ferrocenylsulphonamide 16 and the novel bridged [2]ferrocenophanethiazine 1,1-dioxide 17 24>. The yield of 17 varied with the nature of the solvent, being 13.3% in cyclohexane, 67% in benzene, and zero in dimethyl sulphoxide or DMSO/benzene 25>. 

The same products are also formed in the photolysis of 21a in dioxane in the presence of dimethyl sulphoxide (equation 57)113,114, and the fact that silatriene 21a is quenched rapidly by dimethyl sulphoxide in the same solvent [k = (3.0 0.2) x 109 M-1 s 1] indicates that the reaction involves the intermediacy of the silene47. Reaction of the sulphoxide with 21a presumably involves an intermediate, such as (singlet) 77 (equation 57), that... 

Photolysis of sulphonyl azides in the presence of nucleophilic trapping agents such as dimethyl sulphoxide or dimethyl sulphide gave imine derivatives. For example, irradiation of -toluenesulphonyl azide in dimethyl sulphide gave a 54% yield of iV-( -toluenesulphonyl) dimethylsulphimine (375) The use of dimethyl sulphoxide resulted in lower yields of the trapped nitrene (377) (13-32%), and... 

Iminosulphurans and iminooxysulphurans were obtained by photolysis of azides in sulphides or sulphoxydes. Benzoyl azide in dimethyl sulphoxide yielded compound 117 . 

The photolyses of H2Se,118 dimethyl sulphide, dibutyl sulphide, and methyl vinyl sulphide,119 and dimethyl sulphoxide,120 the role of concerted and hot biradical reactions in the photolysis of thietan and thietan-cyclopentadiene mixtures,121 and the photolysis of aromatic sulphur compounds122 have been reported. 

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