Triazines. Part III. The interaction of substituted diguanides with isothiocyanate esters

Abstract

1-Phenyldiguanide reacts with isothiocyanate esters in dimethylformamide to yield, depending on the conditions and the isolation procedure, either 2-substituted 1-phenylisomelamines, or 1-substituted hexahydro-6-imino-4-phenylimino-s-triazine-2-thiones as main products. Appreciable quantities of other s-triazine derivatives arise in side reactions in each case. The formation of all products is accounted for satisfactorily by a mechanism involving the initial formation of labile open-chain adducts which yield the observed s-triazines by loss of hydrogen sulphide, ammonia, or arylamine, respectively.

1,2-Diphenyldiguanide yields, by the general reaction, 6-substituted 1,2-diphenylisomelamines. The observation that the 1,2,6-triphenyl compound is also formed from N-amidino-N′-phenylthiourea and diphenylcarbodiimide under the usual conditions provides support for the general mechanism proposed for this group of reactions.

Hexahydro-6-imino-1-phenyl-4-phenylimino-s-triazine-2-thione is convertible, by successive S-alkylation and aminolysis, into s-triphenylmelamine. Other properties, including the ultraviolet spectra, of the new types of s-triazine derivatives are described and discussed.