Efficient access to fluorescent benzofuro[3,2-b]carbazoles via TFA-promoted cascade annulations of sulfur ylides, 2-hydroxy-β-nitrostyrenes and indoles

An efficient, TFA-promoted cascade annulation of sulfur ylides, 2-hydroxy-beta-nitrostyrenes and indoles was established. This reaction results in the construction of a diverse set of fluorescent benzofuro[3,2-b]carbazoles with the generation of seven new bonds and two new rings in a one-pot transformation. A plausible mechanism for this reaction was proposed. Moreover, the photo-physical properties of the benzofuro[3,2-b]carbazoles were observed to be simply tuned by changing the electronic nature of the peripheral substituents in the core.