A literature survey showed that different derivatives with the 9-phenyl-9H-carbazole or the dihydroindoline scaffold may be of
biological activity including cytotoxic effect. Driven by this experience, P-functionalized derivatives of these N-heterocycles were synthesized. Three N-heterocycles, 9-(4-bromophenyl)-9H-carbazole, 3-bromo-9-phenyl-9H-carbazole and 1-(5-bromoindolin-1-yl)ethan-1-one, were coupled with dialkyl
phosphites and diarylphosphine
oxides using
Pd(OAc)2 (10 %) as the catalyst precursor and
triethylamine as the base in
ethanol under microwave irradiation. The excess of the Y2 P(O)H
reagent (Y=
alkoxy, aryl) (30 %) served as the P-
ligand in its trivalent tautomeric form (Y2 POH), hence there was no need for the usual P-
ligands meaning cost and environmental burden. Hence, the presented method is a "green" approach that proved to be more efficient than the preparation by the traditional method. The products, dialkyl
phosphonates and tertiary
phosphine oxides obtained in 58-84 % yields were characterized, one of them also by single crystal X-ray analysis, and were subjected to in vitro
biological activity evaluation. A (carbazol)yl-
phenylphosphonate, an N-phenyl-(carbazol)yl-
phosphonate, a (carbazol)yl-phenylphosphine
oxide and an N-phenyl-(carbazol)ylphosphine
oxide revealed a significant cytotoxic activity on A549 human
non-small-cell lung carcinoma and MonoMac-6
acute monocytic leukemia cancer cells. The cytotoxic effect was significant as compared to that of the reference compounds.