Reaction of isothiocyanates with thiourea and amidinothioureas: Formation of S-(N-substituted thiocarbamyl)isothioureas and 1-Alkyl(or aryl)-4-imino(or arylimino)-6-iminohexahydro-1,3,5-triazine-2-thiones

Abstract

Alkyl and aryl isothiocyanates react with thiourea in the presence of alkali to yield S-(N-substituted thiocarbamyl)isothioureas. The products are identified by their chemical and mass spectral characteristics.These compounds yield 5-imino-2-alkyl(or ary1)imino-1,3,4-dithiazolidine salts when oxidized in acid medium. The parent compounds are regenerated from these dithiazolidines on reduction with hydrogen sulphide.� Condensation of isothiocyanates with amidinothiourea and aryl amidinothioureas on the other hand yields 1-alkyl(or aryl)-4,6-diiminohexahydro-1,3,5-triazine-2-thiones and 1-alkyl(or ary1)-4-arylimino-6-iminohexahydro-1,3,5-triazine-2-thione respectively.Plausible mechanisms for these reactions are discussed.

Dithiobiuretes in reactions with electrophilic acetylenes. New derivatives of 1,3,5-dithiazines,-thiadiazines and-triazines as the products of competing reactions of nucleophilic cycloaddition

“…As shown experimentally, these compounds are prone to ring opening, perhaps due to the electrostatic repulsion of large-size sulfur atoms at the methyne carbon atom or to the recyclization to the more stable 1,3,5-triazine (7) and 1,3,5-thiadizine (8). With 2,4-dithiobiurete (2 a) [6] and its mono-substituted analogs (2 b, c; R 2 = H), the presence of one more proton at the terminal nitrogen atom results in the formation of a transition complex (B) and leads to sulfur atom elimination forming (thiocarbamoyl)carbodiimides (D) and/or (thiocarbamoyl)isothiocyanates [7] (Scheme 2).…”

“…In benzene and acetonitrile at 20ºC, a mixture of 1,3,5-triazine (7), 1,3,5-thiadiazine (8), and benzoylvinylthiourea (6) is formed in the ratio (7): (8):(6) º 2 : 2 :1. It should be noted that when the reaction is carried out at a (1) : (2e) ratio of 2:1 the absolute yield of 1,3,5-thiadiazine (8) increases.…”

“…In aprotic solvents (C 6 H 6 , MeCN), however, further reaction is dependent upon the spatial arrangement of the isothiobiurete fragment Another reaction product, 2-(benzoylmethyl)-4-(¯-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), is probably formed as a result of intramolecular cyclization of the intermediate S,S-di(¯-benzoylvinyl)-2,4-isodithiobiurete (O). In previous work, we have isolated an analogous intermediate product [6].…”

“…Mono-and disubstituted 2,4-dithiobiuretes (2 b-e) were synthesized using techniques described earlier [8,9].…”

“…178{180ºC (m.p. 180ºC [8] After isolation of compound (7), the mother liquor was evaporated to 1/3 volume in air at 20ºC. To the solution, 10 ml of benzene was added, stirred, and allowed to stand at 5{8ºC for 24 h. The precipitate was¯ltered o®, washed with 2 ml of cold benzene, and dried in vacuum to give 0.34 g (30%) of 1,3,5-thiadiazine (8) as a yellow powder.…”