Poly(phosphoric acid) (PPA)-Promoted 5-exo-Cyclization of Iminium Ions Generated In Situ: A Facile Access to Functionalized Indene Derivatives

Abstract

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.

Key words

indenes - iminium ions - indanones - exocyclization - polyphosphoric acid - cascade reaction

• References and Notes

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