Synthesis of Dithiocarboxylic Acids and their Derivatives

Methyl dithiocinnamate was obtained in low yield from styrylmagnesium bromide by reaction with CSj and methylation with Mel, and in better yield by bw-temperature thiolysis of the thioimidate (117). At room temperature the thiolysis was complicated by addition of HjS to give the saturated sulphide analogous to (114). The dithiocinnamate dimerizes reversibly, by [4 + 2]cyclo-addition, to form a product that was assigned the structure (118) on n.m.r. evidence. 

The synthesis of dithiocarboxylates by addition of CSj to enamines or activated methylene groups is further exemplified in the pyrimidine and in the 

Tominaga, H. Okuda, Y. Mitsuomi, Y. Matsuda, G. Kobayashi, and K. Sakemi, Heterocycles, 1979, 12,503. 

Yoshida, S. Yoneda, T. Kawase, and M. Inaba, Tetrahedron Lett., 1978, 1285. 

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Synthesis of Dithiocarboxylic Acids and their Derivatives.—The preparation of thioterephthalic acid from l,4-di(chloromethyl)benzene, sulphur, and sodium methoxide (see Vol. 5, p. 179) has beeil reported by another group. In a similar reaction, the addition of chloroacetonitrile to sulphur and triethylamine in DMF, followed by alkylation, gave methyl and ethyl cyanodithioformates. These were not isolated, but they condensed when water was added, giving EfZ mixtures of l,2-di(alkylmercapto)-l,2-dicyanoethylenes. Ethylene dithioacetals from aromatic aldehydes are decomposed by sodium hydride in DMF containing HMPA, with elimination of ethylene and the liberation of an aryIdithiocarboxylate anion this may be alkylated to give the dithioester (Scheme 8). ... 

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