Synthesis and Reactions of Some Novel Triazolo‐, Azolo‐, Tetrazolo‐Pyridopyrimidine and Their Nucleoside Derivatives

Pyridopyrimidine reacted with aromatic aldehydes afforded the arylhydrazone 2a,b which could be cyclized into the pyrido[2,3‐ d ][1,2,4]triazolo[4,3‐ a ]pyrimidine 3a,b , with formic acid, and carbon disulphide to give pyrido[2,3‐ d ][1,2,4]traizolo[4,3‐ a ]pyrimidine 4, 5. Reaction of 1 with nitrous acid afforded tetrazolo[1,5‐ a ]pyrido[2,3‐ d ]pyrimidine 6 , which was reduced by zinc dust to give 2‐amino‐pyrido‐[2,3‐ d ]pyrimidine 7. Finally the reaction of 2‐hydrazino 1 with D‐xylose or D‐glucose afforded the acyclic N‐nucleoside 8, 11 which were converted into tetra/penta O ‐acetate acyclic C ‐nucleoside 9, 12 in acetic anhydride/pyridine. De‐acetylation of compounds 9, 12 afforded C ‐nucleosides 10, 13.