Benzofulvenes are key privileged scaffolds present in natural products, biologically and pharmacologically active molecules, functional materials, and metallocene catalysts. Due to its significance, it is still of considerable interest and necessity to develop efficient synthetic methods for functionalized benzofulvenes. Recently, N-sulfonyl-1,2,3-triazoles, easily obtained from click reactions, have been used for the preparation of a large number of heterocyclic and carbocyclic compounds through Rh-catalyzed denitrogenative cyclization.
On the basis of these results, Rh-catalyzed denitrogenative cyclization of (E)-ethyl 2-(1-alkyl and arylsulfonyl-1H-1,2,3-triazol-4-yl)-3-aryl acrylate generated from (E)-ethyl 2-benzylidenebut-3-ynoates and N-sulfonyl azides in the presence of a copper catalyst was demonstrated for the synthesis of a wide range of functionalized benzofulvenes. Additionally, we have developed straightforward synthetic procedures for three benzofulvenes through tandem Cu-catalyzed [3 + 2] cycloaddition and Rh-catalyzed denitrogenative cyclization from (E)-ethyl 2-benzylidenebut-3-ynoates and N-sulfonyl azides in a one-pot.