ChemInform Abstract: REACTION OF DITHIOBIURET WITH α‐ACETYLENIC KETONES

Abstract

Durch Reaktion der Acetylenketone (I), die über eine aktivierte Acetylenfunktion verfügen, mit Dithiobiuret im Molverhältnis 4:1 werden die Bis‐ketovinylsulfide (IIIa) bzw. (IIIb) als E/E‐,E/Z‐ und Z,Z‐Gemische erhalten.

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

“…Earlier we reported that the interaction of benzoylacetylene with 2,4-dithiobiurete in MeOH and MeCN is accompanied by elimination of a sulfur atom from the molecule of nucleophilic reagent, leading to the formation of bis(¯-benzoylvinyl)sul¯de [6].…”

“…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).…”

“…When 1,3,5-dithiazine (5) is re°uxed in benzene for an hour, the compound is almost completely transformed to the substituted thiourea (6). Similar treatment of 1,3,5-dithiazine (5) in boiling AcOH results in an increased content of 1,3,5-triazine (7) (¹ 30% compared to ¹ 15{17% in the reaction undertaken in AcOH at 20ºC).…”

“…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 MeOH at 0ºC the reaction mixture contains compounds (5), (7), and (8) in the 1 : 1 : 1 ratio and a small amount (¹ 5 %) of (6).…”

“…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].…”