Methyl sulphide radicals, reactions

Bromoisoquinoline did not react with MeS ions in liquid ammonia, but 80% yield of the substitution product 4-isoquinolyl methyl sulphide was formed in the presence of amide ions. Isoquinoline and many other nitrogen-containing heteroaromatic compounds are known to react with amide ions to give anionic adducts 242289, which have been proposed to initiate the S l reaction by an ET to the substrate, which leads to the hetaryl radical. The radical couples only with MeS" ions 29°. 

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. 

In the dehalogenation of 4-chlorobiphenyl, 1-chloro- and 1-bromonaphthalene, 9-chloro- and 9-bromoanthracene and 4-chlorobenzonitrile, diethyl sulphide has been used as electron donor397. The involvement of radical anions in these reactions is evidenced by the incorporation of deuterium into the products when the reactions were performed in acetonitrile-deuterium oxide. Lithium diisopropylamide in hexane or tetrahydrofuran398 and sodium methyl siliconate (MeSi03Na3)399 have also been used as electron transfer reagents in the photodehalogenation of 4-chlorobiphenyl. 

The proofs for the above constitutions are as follows (i) Thymol yields cymene, i-methyl 4-iso-propyl benzene, by loss of the hydroxyl oxygen by means of phosphorus penta-sulphide. (2) Carvacrol may be synthesized from potassium cymene sulphonate by fusion with potassium hydroxide. Therefore both must be mono-hydroxy cymenes. (3) Thymol by means of phosphorus pentoxide splits off the iso-propyl radical yielding meta-cresol and propylene. (4) Carvacrol by the same reaction yields ortho-cresol. Therefore in thymol the hydroxy group is meta to the methyl group while in carvacrol it is ortho. The following relationships are thus established. 

Mechanistic studies with sulphonium salts concern decomposition kinetics in hydroxylic solvents H- H exchange of the a-protons of methyl and allyl-sulphonium salts, the relative rates of which are strongly dependent upon both solvent and micellar effects radical chain reactions of triarylsulphonium halides and sodium alkoxides, which lead to arenes, anisoles, diaryl sulphides, and aldehydes or ketones and the catalysis of hydrocarbon autoxidation by... 

The reaction of thiiran with aryldiazonium chlorides in the presence of copper chloride yields jS-chloroethyl aryl sulphides and diaryl disulphides via radical intermediates (Scheme 4). Treatment of thiirans with sodium methyl xanthate... 

Phenyl radicals react with 1,2,3-benzothiadiazole to give diphenyl sulphide, dibenzothiophen, thianthrene, 4-phenylthiodibenzothiophen, and l,2-bis(phenyl-thio)benzene. It is suggested that the reaction involves attack of phenyl radicals on the sulphur atom of the reactant, to produce an intermediate o-(phenylthio)-phenyl radical, from which each of the products may be derived. Similarly, methyl radicals yield a mixture of thioanisole, thianthrene, 4-methylthiodi-benzothiophen, and l-methylthio-2-phenylthiobenzene. The experiments are claimed to be the first examples of the attack of a radical on a hetero-aromatic sulphur atom (see Vol. 3, p. 678). 

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