Metal-free synthesis of tricyclic benzofuro[2,3-]pyridin-3-ol derivatives, characterization, and photoluminescence properties.

This paper presents a metal-free synthetic protocol for assembling novel benzofuro[2,3-]pyridin-3-ols (BFPYOLs) using 2,3-disubstituted benzofuran derivatives with good yield. The method's advantages include the absence of an expensive metal catalyst, organic ligands, and easily accessible starting materials. The photophysical properties of the synthesized BFPYOLs are investigated, revealing that the largest is displayed by compound 7g at 389 nm, while the largest is observed in compound 7i at 494 nm in DMSO solvent. This highlights the significant impact of substituents on the compounds. Additionally, the solvatochromic and thermal effects of compound 6j are analysed. Among the tested BFPYOLs, the highest photoluminescent quantum yield (PLQY) was exhibited by 7k, achieving 91% in DMSO solvent. This study demonstrates that our synthetic methodology and the synthesised BFPYOLs can provide a powerful gateway to the generation of novel economic fluorescent probes.