1.2.4- Triazolo quinazolines 1,5-diamino

A particularly interesting example of this method of synthesis is the cy-clrzation of the 4-amino-3-(2-aminophyenyl)-l,2,4-triazoloes 73 with cyanogen bromide. Primarily, this reaction was applied to synthesize the 6-amino-l,2,4-triazolo[4,3-d]benzodiazepine hydrobromides 74 the obtained products, however, were found to be the l,5-diamino-l,2,4-triazolo-[l,5-c]quinazolin-ium bromides 77. Structure elucidation of 77 was accomplished by direct... 

Hu et al. (91 Mil) report the Dimroth rearrangement of 2-hydrazino- to 2,3-diamino quinazolin-4-ones under catalysis of carboxylic acid derivatives this reaction is followed by an in situ cyclization in which the same carboxylic acid derivatives serve as Cj-synthons. l-Acylamino-2-alkylthiopyrimidines are hydrazinolyzed and cyclized to 3-amino-1,2,4-triazolo[l,5-a]pyrimidinium salts (89EGP270711). 

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