Heterocycles from substituted amides. IX. 4,5-dihydro-1,2,4-triazin-6-(1H)ones from 2-isocyanoacetates and hydrazine

The novel synthesis of 4,5-dihydro-1,2,4-triazin-6-(1H)ones, 2 , from 2-isocyanoacetates is described. This synthetic method allows the first synthesis of the unsubstituted parent ring sytem and, in general, gives 2 substituted in only the five position. The assignment of tautomeric structures ( 2 or 3 ) to the triazinone products was resolved by spectroscopic means.