Synthesis and fluorescence properties of benzoxazole-1,4-dihydropyridine dyads achieved by a multicomponent reaction

Photoactive 2-(2′-hydroxyphenyl)benzoxazole-1,4-dihydropyridine (HBO–DHP) dyads were obtained by a multicomponent one-pot Hantzsch synthesis using a fluorescent aldehyde, a 1,3-dicarbonylic compound and ammonium acetate. The key step in this synthetic methodology was the synthesis of the formyl benzoxazole derivative through a Duff-modified functionalization protocol. UV-Vis absorption and fluorescence emission spectroscopies were also applied to better understand the photophysics of these compounds. The three novel fluorescent compounds were obtained in moderate yields as stable solids with absorption in the UV region and emission in the blue-green region. Preliminary results indicate that after excitation both HBO and DHP fluorophores behave independently in the HBO–DHP structure.