Unexpected synthesis of benzimidazole from Schiff base mediated by lanthanide chloride and citotoxic activities

•Synthesis of the BenzHCl from Anisalophen with chloride lanthanide was carried out.•The mechanism of the reaction is proposed from different synthetic strategies.•The single-crystal X-ray structure of the BenzHCl is discussed.•Thermal stabilities of Anisalophen and BenzHCl were analyzed by TG/DTA techniques.•Cytotoxicity of compounds was investigated against HFibro, MCF7 and MDA-MB-231 cells. Schiff bases and benzimidazoles compounds exhibit an extensive range of therapeutic applications, such as anticancer agents. The present study shows the synthesis of the 2-(4-methoxyphenyl)-1H-benzimidazole hydrochloride (BenzHCl) from N,N’-bis-(4-methoxybenzylidene)-benzene-1,2-diamine (Anisalophen) mediated by chloride lanthanide (Gd3+, Tb3+, or Eu3+). The mechanism of the reaction is proposed from different synthetic strategies. BenzHCl crystallizes in the monoclinic system, space group P21 and shows the iminic nitrogen atom protonated, which is stabilized by the chlorine ion. BenzHCl and Anisalophen were characterized, and their thermal stabilities were analyzed by TG/DTA techniques. Anisalophen and BenzHCl showed higher cytotoxic activity against human breast cancer cells (MCF-7 and MDA-MB-231) when compared to human fibroblast cells. [Display omitted]