1,2,3a-Triazaindene 1,2,4-Triazolo[4,3-a]pyridine 1,2-Diazaindolizine 274-80-6 NSC68457 Pyrido[2,1-c]-1,2,4-triazole Pyrido[2,1-c]-s-triazole s-Triazolo[4,3-a]pyridine