PdCl₂-Catalyzed Domino Reactions of 2-Alkynylbenzaldehydes with Indoles: Synthesis of Fluorescent 5H-Benzo[b]carbazol-6-yl Ketones

摘要

Synthetic methods: A new, selective Pd-catalyzed domino reaction of 2-alkynylbenzaldehydes with indoles has been developed for the synthesis of 5H-benzo[b]carbazol-6-yl ketones. The isobenzopyrylium complex is trapped by indole at room temperature to give 3-(1H-isochromen-1-yl)-1H-indoles, which can be transformed into 5H-benzo[b]carbazol-6-yl ketones by raising the temperature (see scheme). These ketones exhibit intense fluorescence and interact with metal ions to enhance the fluorescence intensity.