A facile and efficient synthesis of indole and acridine derivatives using (MWCNTs)-COOH/La2O3 nanostructure

Acid functionalized multi-walled carbon nanotubes (MWCNTs)-COOH were reacted with La(NO3)3.6H2O in acetic acid by ultrasonication at 60oC to gain (MWCNTs)-COOH/La2O3 hybrid. This nano-material was used as an efficient catalyst for the synthesis of some heterocycles containing nitrogen. Acridine and indole derivatives were obtained by the reaction of isatin or dimedone with some amino compounds such as thiosemicarbazone, amino acids, and anthranilic acid using (MWCNTs)-COOH/La2O3 (5 mol%) in ethanol under reflux conditions. The products were gained in mild reaction conditions and good yields and identified by CHN analysis, NMR, and FT-IR spectra. The amount of La or La2O3-loading in (MWCNTs)- COOH/La2O3 was measured using the inductively coupled plasma–atomic emission spectroscopy (ICP-AES) analysis. The leaching of catalyst was measured using a hot filtration method. There was no leaching to confirm the stability of the catalyst. The catalyst was simply separated at the end of the reaction, washed, dried, and re-entered to a fresh reaction mixture 5 times without considerable loss of activity