Synthesis and photoluminescence properties of star-shaped 2,3,6,7-tetrasubstituted benzo[1,2-b:4,5-b′]difurans

Abstract

A new reaction of α-haloketones with hydroquinones leading to highly fluorescent star-shaped 2,3,6,7-tetrasubstituted benzodifurans is described. Thus 2,3,6,7-tetrakis(4-bromophenyl)-4,8-didecylbenzo[1,2-b:4,5-b′]difuran, the core of benzodifuran stars, was obtained from 1,2-bis(4-bromophenyl)-2-chloroethanone and 2,5-didecyhydroquinone in the presence of zinc chloride without a solvent. Elongated benzodifuran derivatives were obtained by the reaction of tetrabromobenzodifuran with aryl-, heteroaryl- or vinylboronic acid MIDA esters in the presence of Pd(dppf)Cl2 catalyst, and tripotassium phosphate as a base in 1,4-dioxane/water mixture. The star-shaped products, obtained in 37–99% yield, exhibit the UV–Vis fluorescence with high quantum yields, 69–100%. Due to the long-chained alkyl groups at positions 4 and 8, these highly π-conjugated products are soluble in many organic solvents.