Triazines. Part IV. The interaction of diguanide and its homologues with isocyanate esters

Abstract

Diguanide reacts slowly with isocyanate esters in dimethylformamide at 100° to give 1-substituted hexahydro-4,6-di-imino-s-triazin-2-ones with small quantities of ammeline. The structure assigned to the s-triazine-6-ones follows from their mode of formation, their general chemical behaviour, and their alternative production from the 2-thiones by oxidative desulphuration.

1,2-Diphenyldiguanide and aromatic isocyanates similarly yield 1-arylhexahydro-4-imino-6-phenylimino-s-triazin-2-ones, the structure of which is established unequivocally by this synthesis.

The use of 1-phenyldiguanide in this general reaction yields four main products: 6-amino-4-anilino-s-triazin-2-ol, 1-substituted hexahydro-4,6-di-imino-s-triazin-2-ones, 1-substituted hexahydro-6-imino-4-phenylimino-s-triazin-2-ones, and 1-substituted hexahydro-4-imino-6-phenylimino-s-triazin-2-ones. The nature of the isocyanate determines which of these triazines predominate. Certain chemical properties, and the ultraviolet spectra of the new substituted ammelines are discussed.

The entire group of reactions is accounted for in terms of the addition–elimination mechanism involving intermediate adducts derived from equimolar quantities of the reactants. Since loss of water from carbamoyl compounds of this type occurs much less readily than loss of hydrogen sulphide from their thiocarbamoyl analogues, melamines are not formed in this reaction.