6-Nitro-1,2,4-triazolo pyrimidine

Ring opening of also a fused [l,2,4]triazole system by secondary amines has been reported. Chupakhin et al. described that 5-methyl-6-nitro[l,2,4]triazolo[l,5-r ]pyrimidin-7(8/f)one 122 underwent ring opening when treated with various secondary amines to yield pyrimidyl ureas 123 in medium to good yield <2001IZV655>, as shown in Scheme 14. 

Another interesting rearrangement, involving a pyrimidine-pyridine ring transformation combined with a Dimroth rearrangement, is observed when 6-nitro[l,2,4-triazolo][l,5- ]pyrimidine (74) reacts with ethyl cyanoacetate. 

Cyclization of 5-methoxy(nitro)-4-hydrazinopyrimidines (485) with tri-ethyl orthoformate gave the l,2,4-triazolo[4,3-c]pyrimidine intermediate 486, which cannot be isolated due to its conversion to its [1,5-c] isomer 487 by a Dimroth rearrangement. However, the 5-benzyloxypyrimidine derivative, under the same conditions, afforded a mixture of the 8-benzyloxy derivatives of both [4,3-c] and [l,5-c]isomers 486 and 487, respectively (86TL3127 89JHC687 90H277) (Scheme 95). 

Corrosion inhibitors, [1.2,4]triazino[4,3-ojbenzimidazoles, 59, 155 Coulson-Rushbrook theorem, 55, 273 Coumarins, see l-Benzopyran-2-ones Coupling reactions, trifluoromethyl iodide with aryl halides, 60, 12 Covalent hydration in 6-nitro-l 1,2,4]triazolo[ 1,5-a)-pyrimidines, 57, 107 of coordinated ligands, 58, 138 Creutz-Taube ion, 58, 124 Criss-cross cycloadditions, of... 

TRIAZOL-5-ONE, 3-NITRO- see NMP620 (l,2,4)TRIAZOLO(4,3-a)PYRIMIDINE see THT280 TRIAZOTION (RUSSIAN) see EKNOOO... 

When the six-membered ring is strongly activated, e.g. by a 6-nitro substituent, nucleophilic attack by alcoholic alkali may lead to rearrangement as in Scheme 15 (81T3423). These reactions are analogous to those occurring in the corresponding 1,2,4-triazolo-pyridine and -pyrimidine systems. 

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