A study on the reaction of 16-dehydropregnenolone acetate with 2-aminobenzimidazole

[Display omitted] •The reaction between 16-dehydropregnenolone acetate and 2-aminobenzimidazole was investigated as an easy way to obtain pyrimidinobenzimidazole derivative.•The reaction mechanism based on experimental evidences as well as DFT calculations was proposed.•D-homo ketone byproduct was formed in α-ketol type rearrangement.•The strong solvent effect on the condensation process was revealed. The condensation of 16-dehydropregnenolone acetate with 2-aminobenzimidazole was studied. The polycyclic aromatic product was formed as a single regioisomer in a cascade reaction comprising addition, cyclization, autoxidation, and aromatization, in addition to the rearranged D-homo product. The reaction mechanism based on DFT calculations is proposed.