In this letter, we report the regioselective iodocyclization reaction of 3-alkynyl-2-(methylthio)quinolines and 3-alkynyl-2-(methylseleno)quinolines for the synthesis of thieno[2,3-b]quinoline and selenopheno[2,3-b]quinoline derivatives. Furthermore, by employing various palladium-catalyzed Sonogashira, Suzuki, and Heck reactions, the structural diversification of the resulting halide derivatives, which can act as the important intermediates for building other valuable compounds, was achieved. All compounds were fully characterized by the FT-IR, mass, 1H NMR, and 13C NMR spectral data. Finally, the structure of the thieno[2,3-b]quinoline derivative was confirmed by X-ray crystallography. This methodology provided a novel pathway to access quinoline fused heterocycles via iodocyclization reaction. Furthermore, the reaction process was well elucidated by density functional theory calculations.

Synthesis of thieno[2,3-b]quinoline and selenopheno[2,3-b]quinoline derivatives via iodocyclization reaction and a DFT mechanistic study.

A simple route for preparation of 4-substituted thieno/furo[2,3-c]quinoline compounds is reported in this paper. These compounds were synthesized by using Suzuki coupling between appropriate boronic acid and 2-iodoaniline, followed by reaction with diverse aldehydes in the presence of a catalytic amount of FeCl3. Naphthyridine analogues were also prepared in order to demonstrate the efficacy of the developed method. Further anti-tubercular activity screening of the molecules was undertaken, wherein compounds bearing a fused furo[2,3-c][1,8]naphthyridine skeleton displayed highest activity. The best MIC (minimum inhibitory concentration) value of 5.6 μmol was obtained for 4-(4-methoxyphenyl)furo[2,3-c][1,8]naphthyridine, which is found to be superior to the existing first line anti-tubercular drug ethambutol (7.6 μmol).

Synthesis and anti-tubercular activity of fused thieno-/furo-quinoline compounds

This work presents an efficient, easy and green method for the benzimidazoles and benzothiazoles synthesis by a condensation reaction of 1,2-diamino benzene and 2-amino thiophenol with various aromatic aldehydes using SnP2O7 as a new heterogeneous catalyst. This catalyst was prepared by adding MAP to the solution of SnCl2 and characterized by microscopic and spectroscopic methods namely X-ray diffraction, scanning electron microscopy and infrared which proved that the chemical structure of MAP has been modified when SnCl2 was added leading to the formation of SnP2O7. On the other hand, the reaction conditions were optimized namely the nature of the solvent and the mass of the catalyst. The high yields (85–97%) and very short reaction times (5–40 min) obtained for various benzimidazoles and benzothiazoles derivatives synthesis show that the new catalyst is very interesting because of its good catalytic activity and its reusability for at least five cycles without any degradation of its activity.

Preparation of tin-modified mono-ammonium phosphate fertilizer and its application as heterogeneous catalyst in the benzimidazoles and benzothiazoles synthesis

B. Kishore

Papers

A novel approach toward the synthesis of azetidinones derivatives