Sonogashira coupling of quinoxaline-o-sulfonates leading to heterocyclic compounds with potential medicinal properties against TB

Thesis (MSc. (Chemistry)) -- University of Limpopo, 2015

Alkyne-quinoxaline compounds were successfully synthesised form the cross-coupling of 2-benzenesulfonyloxyquinoxaline with terminal alkynes. The current study demonstrates the ability of benzenesulfonyloxy as a good leaving group in Sonogashira coupling reaction, generating a number of alkyne-quinoxaline compounds. The structures of the synthesised compounds were characterised through the comprehensive analysis of spectroscopic data from NMR, HPLC-MS and others selected compounds with IR. Several alkyne-quinoxaline compounds were synthesised in moderate to good yields. During analysis, it was observed that the highest yield was obtained when using 4-(trifluoromethyl)phenylacetylene 4e and the lower yield was obtained when using the 3-ethynylthiophene 4s as a substrate. The alkyne-quinoxaline compounds were investigated for 1,3-dipolar cycloaddition which was done from 2-ethylquinoxaline 6. The 1,3-dipolar cycloaddition reactions were successful and the compounds were obtained in good yields. The in vitro analysis on anti-tubercular screening against H37RvMA strains of M tb reveals that compounds 5e and 5o which contained a trifluoroanisole moiety showed promising activity amongst all the synthesised compounds. The compounds were having MIC90 values 11.8 μM and 12.7 μM respectively, however, they were found to be less active than rifampicin. Compounds 5a, 5b, 5e, 5g, 5h, 5i, 5I, and 5r were evaluated for anti-cancer activity on A549 cells. The results have showed that 5i was able to retard the migration of A549 cells in the Wound-Healing Migration Assay.

National Research Foundation (NRF) Sasol Inzalo Foundation