Nucleophilic ring-opening of the azole and azine moieties in 6-nitro-1,2,4-triazolo[1,5-a]pyrimidin-7-ones

Abstract

The effects of the nature of the nucleophile and the structure of 6-nitrotriazolo[1,5-a]pyrimidinones on the direction of the ring opening were investigated. The triazole ring is opened under the action of strong bases, such as alkoxides or alkalis, to form 2-cyanoaminopyrimidinones and then 2-aminopyrimidinones. The results of the reactions with N-nucleophiles depend on the accessibility of position 5 of the heterocycle. Thus, sterically hindered secondary amines react with 5-methyltriazolopyrimidinones to give 2-guanidinopyrimidinones and then 2-aminopyrimidinones. In the absence of a substituent at position 5, the azine ring is opened to form 4-alkyl-3-amino-1,2,4-triazoles and 3-amino-2-nitroacrylamides. Under the action of primary amines, only the pyrimidine fragment is cleaved.