Synthesis and ring closure reactions of pyrido[3,2,1-jk]carbazol-6-ones

4‐Hydroxy‐5‐phenylpyrido[3,2,1‐jk]carbazol‐6‐ones (4, 5), which were obtained from carbazoles 1 and malonates 2 or 3, were converted to reactive intermediates such as 4‐chlorides 9 or 4‐tosylates 10, which gave in turn 4‐azido‐5‐phenyl derivatives 11. 5‐Alkyl‐4‐azides 11 were not obtained in this manner; however a new one‐pot azidation reaction was developed starting from 4‐hydroxy derivatives 4 which gave azides 11 in good yields. 4‐Azido‐5‐phenyl derivative 11f cyclized on thermolysis to the indole 12. The thermal behaviour of the azides 11 was studied by thermoanalytical methods (DSC).