A metal-free Brønsted acid promoted two-component reaction between cinnamaldehydes and sulfonamides is described. This cascade process provides a simple and atom-economical alternative synthesis of a range of functionalized indenes from easily available starting materials. The resulting N-indenylsulfonamides were readily converted into the corresponding indenylenamines or indanones.

A simple AlCl 3 -catalyzed condensation/cyclization cascade process between aldehydes and sulfonamide is reported, in which two new bonds and one five-membered ring are simultaneously formed with water as the byproduct. This method provides a rapid access to indenamine and 9-aminofluorene derivatives. Additionally, these products can be transformed into corresponding indanones and fluorenones under the developed conditions.