Fig. 2
Synthetic methodology for Indole diazenyl derivatives (DS1–DS-21). Reagents and conditions: (a) NaNO2/HCl, 0 °C, (b) indole/nitroindole, acetic/propionic acid mixture (8:2), 0 °C, (c) Na2CO3, (d) ethanol, 5–7 drops of acetic acid, reflux for 7–8 h, (e) furfurylamine, (f) ethyl acetoacetate, triethylamine, sulphur, stirring for 10–15 h at RT, (g) POCl3, thiosemicarbazide, reflux for 6–7 h at 70 °C, (h) 4-aminoantipyrine, (i) N-1-napthylethylenediamine, (j) 2-benzothiazole amine