Azaindoles may be used as intermediates in the preparation of some biologically active substances.¹ They are bioisosteres of an indole moiety varying the position of the nitrogen atom on the benzene core: 4-,5-, 6- and 7-azaindoles.²

Three different synthetic procedures were used to perform the oxidation of 4-azaindol, 5-azaindol, 6-azaindol, 7-azaindol and the indol. The first one³ (a) was carried out by adding bromine into a mixture of 1:1 tBuOH/H₂O; the second⁴ (b) using pyridinium bromide perbromide (PBPB) in a solution of tBuOH; and the last⁵ (c) synthetic methodology utilized pyridinium chlorochromate (PCC)–SiO₂ as oxidizing agent. The results are shown in thefollowing Table 1.

It should be noted that no oxidation was found at the entrances 8 and 9. All products were characterized by ¹H and ¹³C NMR spectroscopy. Nine azaindoles derivatives were synthesized employing three different synthetic methodologies.