A potassium amide induced ring transformation of 1,2,4-triazines into 1,2,4-triazoles and 1,3,5-triazines

Article abstract of DOI:10.1021/jo00377a012

5-Phenyl- and 3,5-diphenyl-1,2,4-triazine, when treated with potassium amide in liquid ammonia, are converted into a mixture of phenyl derivatives of 1,2,4-triazole and amino-1,3,5-triazines. The ring contraction of the 1,2,4-triazine ring into the 1,2,4-triazole ring has been explained by an initial addition of the amide ion to C-6, ring opening by fission of the N1-C6 bond and ring closure (ANRORC-mechanism). The transformation of the 1,2,4-triazine ring into the 1,3,5-triazine ring has been studied by means of ¹⁵N-labeled potassium amide. It was found that the nitrogen of the amide ion becomes one of the ring nitrogen atoms in the 1,3,5-triazine ring and that the exocyclic amino group is imlabeled. Based on these ¹⁵N-labeling studies, it is proposed that this ring transformation starts with an initial addition of the amide ion to C-5, ring opening between C-5 and C-6, a dehydrogenative rearrangement of the open-chain intermediate 1-amino-2,4,5-triazahexatriene into 1-amino-4-cyano-2,4-diaza-1,3-butadiene, and ring closure.