Studies in the dithiole series
McKinnon, David Mackie
Using previously developed methods, several new dithiolium salts have been prepared, and others have been synthesised by modification of Known methods. 3-Benzyl-5-phenyl-I,2-ditniolium perchlorate has been prepared by reaction of benzoylphenylacetone with hydrogen disulphide in ethereal hydrogen chloride, 3-chloro-5-phenyl-i,2-dithiolium perchlorate by chlorination of 5-phenyl-l,2-dithiole-3-thione, and the unsubstituted 1,2-dithiolium cation by peracetic acid oxidation of I,2-dithiole-3-thione. Peracetic acid oxidation of I,3-dithiole-2-thione and its 4-phenyl derivative provided the I,3-ditnioliura system and its 4-phenyl derivative. Cyclisation of S-phenacyl--phenyl (dithioacstate) in ether with boron trifluoride furnished the known 2-benzyl-4-phenyl-l,3-dithiolium cation. The reactions of several dithiolium salts with nucleophilic reagents have been studied. The 1,2-dithiolium cation and its 4-phenyl derivative decomposed by reaction with anionic species to produce l,2-dithiole-3-thiones but the 4-phenyl compound produced 4-phenylisothiazole by reaction with ammonium acetate. Reaction in benzene suspension with ammonia produced bis (4- phenyl-l,2-dithiole-3-yl) sulphide, with aniline it produced cis-phenylmalondialdehydedianil. Related reactions of 5-phenyl and 3,5-diphenyl-l,2-dithiolium per¬ chlorate produced anilinopropenethione derivatives. In cold ethanol methylaniline reacted with 5-phenyl-I,2-dithiolium perchlorate to produce one of the above types of derivatives. In hot ethanol a hydride ion was lost oxidatively to produce 3-(p-methylamino- 5 phenyl^pnenyl-1,2-dithiolium salt. A similar reaction with 4-pheny1-1,2- dithiolium perchlorate failed to give a solid product. 3,5-Dipheny.l-I,2-dithiolium perchlorate reacted with sodium ethoxide to produce 3-ethoxy-3,5-diphenyl-I,2-aithiole. With diethyl-sodiomalonate it furnished 4,b-diphenyl-3-ethoxycarbonyl-thiopyran-2r-one by rearrangement. 2,4,5-Triphenyl-l,3-dithiolium perchlorate reacted with ethoxide and cyanide ions to produce the corresponding 2- substituted tripheny1-1,3- dithiole derivatives. Ammonia gave the 2-amino derivative, but in alcohol or acetic acid this decomposed with-the production of desoxybenzoin,thiobenzamide, triphenyl-I,3-dithiole and triphenyl thiazole.