Regioselective N-alkylation of some imidazole-containing heterocycles and their in vitro anticancer evaluation

Abstract Imidazole-containing heterocycles: Imidazopyridines, imidazopyrimidines and imidazopyra-zines can exist more tautomeric forms than benzimidazoles. Their regioselectivities were determined for N-alkylations with 4-fluorobenzyl bromide under basic conditions (K2CO3) in DMF. We observed that, regioisomers were mainly formed as a mixture in this reaction and N-benzylation occurs at a higher ratio on six membered heterocycles. Their structural assignments were made with the use of two-dimensional 1H–1H NOE (nuclear overhauser effect spectroscopy, NOESY). Complementary structural information was provided by 2D-HMBC spectra of the compounds. Synthesized compounds were tested for in vitro cytotoxic activities against Human colon cancer cell line (HCT-116) and leukemia cell lines (K562 and HL-60) by MTT test. Among them, imidazopyridine analogue 10, bearing bromine atom at the C-6 position of the pyridine moiety, gave the lowest IC50 value with 6–7 μg/mL against all three cancer cell lines.