Application of the Suzuki-Miyaura Reaction for the Postfunctionalization of the Benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinine Core: An Approach toward Fluorescent Dyes.

A fluorescent dye based on the 8-brominated benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinine core was synthesized from benzo[ d]thiazol-2-amine. The new boron complex can be effectively modified by a palladium-catalyzed Suzuki-Miyaura cross-coupling reaction with (het)arylboronic acids. This reaction allows a valuable regioselective postfunctionalization of 1,3,5,2-oxadiazaborinine chromophores with different aromatic substituents. The solutions of obtained target complexes in organic solvents demonstrate high fluorescence quantum yields. The compound with a 4-cyanophenyl group at benzothiazole unit (Ar = 4-C6H4CN) exhibits a comparatively high fluorescence quantum yield of 0.31 in the solid state.