Metal-Free Tandem Friedel–Crafts/Lactonization Reaction to Benzofuranones Bearing a Quaternary Center at C3 Position

A metal-free tandem Friedel–Crafts/lactonization reaction to 3,3-diaryl or 3-alkyl-3-aryl benzofuranones catalyzed by HClO₄ was reported. A variety of tertiary α-hydroxy acid esters could readily react with substituted phenols to afford the desired products in rich diversity. The synthetic utility of the products was demonstrated by the synthesis of polycyclic compounds. ¹H NMR studies supported that this tandem reaction proceeded via tandem Friedel–Crafts/lactonization sequence