Synthesis of New Derivatives Benzo[4′,5′]imidazo[2′,1′:6,1]pyrido[2,3-d]pyrimidine

Abstract

The reactions of 4-methyl- and (RS)-4,6-dimethyl-2-phenyl-5,6-dihydrobenzo[4′,5′]imidazo-[2′,1′:6,1]pyrido[2,3-d]pyrimidines and 4-methyl-5,6-dihydrobenzo[4′,5′]imidazo[2′,1:6,l]pyrido[2,3-d]pyrimi-din-2-ol with aromatic and heterocyclic aldehydes under various experimental conditions were studied. It was shown that the reaction with aldehydes upon boiling in acetic anhydride involves exclusively the 6-methylene group in the a-position to the benzimidazole fragment of the tetracycle and is accompanied by a 1,3-prototropic shift, which results in the formation of 6-aryl(hetaryl)methyl-4-methyl derivatives. The 4-methyl group in the substituted 2-phenyl(hydroxy)derivatives of 5,6-dihydrobenzo[4′,5′]imidazo[2′,1′:6,1]pyrido[2,3-d]pyrimidines reacts with aldehydes only under fusion conditions in the presence of ZnCl₂. The structure of the synthesized compounds was confirmed by one- and two-dimensional (NOESY) ¹H NMR spectroscopy and XRD analysis.