An alternative synthesis of 10H-indolo[3,2-b]quinoline and its selective N-alkylation

A new and a more efficient synthesis of 10H‐Indolo[3,2‐b]quinoline (quindoline) is reported. The synthesis involved N‐arylation of 3‐aminoquinoline with triphenylbismuth diacetate followed by oxidative cyclization using paOadium(II) acetate. A selective N‐alkylation methodology for quindoline was also developed. Alkylation on N‐5 was obtained in sulpholane, while alkylation on N‐10 was achieved in acetone in the presence of potassium hydroxide. A sequential N‐5‐ and N‐10 double alkylation procedure was also formulated.