Acid-Mediated Domino Cyclization of -Formyl Cinnamate Esters: Synthesis of Substituted Indene/Indane Esters and Indeno[]indenones.

A Bro̷nsted acid-driven protocol to access substituted monoarylindene esters, biarylindane esters, and indeno[]indenones from simple -formylcinnamate esters and external arenes has been revealed. Remarkably, this single-pot process enabled the construction of two, three, and four new C-C bonds in building monoarylindene esters, biarylindane esters, and indeno[]indenones, respectively, under metal-free and mild reaction parameters triggering the inactive cinnamate ester moiety. In addition, the present strategy is investigated with widespread substrate scope.