Reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles with primary and secondary alkylamines: novel synthesis of (arylimino)cyanomethyl alkylamino disulfides and their mechanisms of formation

Reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles with alkylamines such as isopropylamine, piperidine, pyrrolidine, and diethyamline in methylene chloride at room temperature gave (arylimino)-cyanomethyl alkylamino disulfides (14-83%) along with N'-aryl-N-alkylcyanoformamidines (0-88%). The yields of the latter increase and those of the former decrease with the concentration of the amine. In addition, some of the latter compounds were independently synthesized by treatment of the former with cyclic amines such as piperidine, pyrrolidine, and morpholine in methylene chloride at room temperature (22-97%). The results indicate that the former compounds are involved as intermediates in the formation of the latter in these reactions. However, when [(p-nitrophenyl)imino]cyanomethyl (pentane-1,5-diyl)amino disulfide was treated with sterically bulky amines such as tert-butyl- and diethylamines at reflux and room temperature, respectively, cyanoformamidines having a piperidine moiety rather than tert-butyl- and diethylamino groups were obtained as the only isolable products. Two pathways which involve initially either direct nucleophilic attack of alkylamines on the imino carbon or on the sulfur α to the amino group of (arylimino)cyanomethyl alkylamino disulfides are proposed to rationalize the results