I2-DMSO-mediated [4 + 2] cyclization of methyl ketone with 2-aminobenzimidazole to construct 2,4-disubstituted benzo[4,5]imidazo[1,2-a] pyrimidines

A novel and efficient synthesis of 2,4-disubstituted benzo[4,5]imidazo[1,2-a]pyrimidine skeletons is reported. Using 2-aminobenzimidazole and acetophenone as substrates, an I₂-DMSO-mediated multicomponent reaction was described, which used a one-pot method to generate two C-N bonds and one C-C bond, yielding 25 substrates. Currently, such derivatives are used clinically for biorevealing, so we selected some of the compounds in this paper for photophysical characterization. Spectroscopic studies showed that the selected compounds have maximum absorption at 250 nm and maximum emission at 600 nm with quantum yields of 0.01-0.08.