Montmorillonite K-10 catalyzed cyclization of N-ethoxycarbonyl-N'-arylguanidines: Access to pyrimido[4,5-c]carbazole and pyrimido[5,4-b]indole derivatives

Abstract Two new heterocycles, pyrimido[4,5- c ]carbazole and pyrimido[5,4- b ]indole, were prepared in three steps from 3-aminocarbazole and 3-aminoindole, respectively. The key Friedel–Crafts intramolecular cyclization was realized under microwave irradiation using montmorillonite K-10 clay as a catalyst. The pyrimido[4,5- c ]carbazole derivative shows significant micromolar IC 50 against cancer cell lines. Unlike similar carbazole and indolocarbazole compounds, the molecule does not interfere with topoisomerase activity.