Reduction of 4,7‐diphenyl‐1,2,5‐thia(oxa)diazolo[3,4‐c]pyridines affording 2,5‐diphenyl‐3,4‐diaminopyridines and ring closure of the diamines to fluorescent azaheterocycles

Reduction of 4,7‐diphenyl‐1,2,5‐thia‐ (1a‐i) and 1,2,5‐oxadiazolo[3,4‐c]pyridines (3a and c‐e) gave 3,4‐diamino‐2,5‐diphenylpyridines (2a‐g), which were converted into the fluorescent triazolo[4,5‐c]‐(5), 1,2,5‐selenadiazolo[3,4‐c]‐ (6), imidazolo[4,5‐c]pyridines (8), and pyrido[5,6‐c]pyridines (11). In the reduction of 3a, c and e, 4,5‐dihydro[1,2,5]oxadiazolo[3,4‐c]pyridines (4a‐c) were obtained.