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

A Bro̷nsted acid-driven protocol to access substituted monoarylindene esters, biarylindane esters, and indeno[ a ]indenones from simple ortho -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[ a ]indenones, respectively, under metal-free and mild reaction parameters via triggering the inactive cinnamate ester moiety. In addition, the present strategy is investigated with widespread substrate scope.