Benzimidazoles have a broad spectrum of biological and pharmacological properties, including anticancer
activity. This study reports the facile synthesis and cytotoxic evaluation of twenty-eight 1,2-disubstituted
benzimidazoles (6a–β), based on condensation reactions between N-benzyl o-phenylenediamine and
benzylamine. The reactions were solvent-free, with the use of Na2S2O5 as an inexpensive and environmentally
friendly oxidizing agent, and progressed rapidly. Cytotoxicity assessments using the 3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed against the A549, HeLa, and MCF-7 cell
lines for all synthesized compounds (6a–β). Among them, 6j, 6k, 6l, and 6n displayed good activities against
the A549 and MCF-7 cell lines. These compounds possessed IC50 values ranging from 2.55 to 4.50 μM, corresponding
to 1.4-fold to 2.4-fold stronger potencies than that of the positive control 5-fluorouracil (5-FU)
(IC50  6.08 μM) against MCF-7 cells, while 6k (IC50  3.22 μM) was consistent with 5-FU on the A549 cell
line (IC50  3.77 μM). Structure–activity relationship analyses revealed the 3-pyridinyl moiety at C-2 and the
CH3, OCH3, or 1,3-dioxolyl groups on the benzene ring at the N-1 position of the benzimidazole heterocycle
as key structural features effectuating the observed cytotoxicities.