Utility of Styrylpyrazoloformimidate in the Synthesis of Fused Heterocyclic Compounds

Abstract

Refluxing of ( E )-5-amino-1-phenyl-3-styryl-1H-pyrazole-4-carbonitrile 2 with triethylor-thoformate in acetic anhydride afforded the corresponding formimidate 3. Treatment of 3 with hydrazine hydrate in ethanol afforded amino imino compound 4. Reaction of 4 with diethyl dicarbonate at reflux gave ( E )-7-phenyl-9-styryl-7H-pyrazolo[4,3- e ][1,2,4]triazolo[1,5- c ]pyrimidine 7. Refluxing of 4 with hydrazine hydrate afforded ( E )-4-hydrazinyl-1-phenyl-3-styryl-1H-pyrazolo[3,4- d ] pyrimidine 8. Treatment of the latter compound 8 with aldehydes in boiling ethanol in the presence of acetic acid afforded the corresponding hydrazone 10. Oxidative cyclization of the hydrazone 10 led to the formation of pyrazolo[4,3- e ][1,2,4]triazolo[4,3- c ]pyrimidine 11. The latter products re-arranged to pyrazolo[4,3- e ][1,2,4]triazolo[1,5- c ]pyrimidines 13. The structures of the new products were established on the basis of elemental analysis and spectral data.