Synthesis of 2,3‐Diarylindanones and 2‐Arylindenes from Trisubstituted α,β‐Unsaturated Esters Derived from Highly Strained 2,3‐Diarylcyclopropenones and Coumarin Derivatives

A novel strategy has been developed for the synthesis of 2,3‐diarylindanones and 2‐arylindenes through the formation of trisubstituted α,β‐unsaturated esters by the ring opening of 2,3‐diarylcyclopropenones in the presence ofa catalytic amount of TPP under mild reaction conditions. Initially, PPh3 activates the diarylcyclopropenone to generate the phosphonium adduct, which simultaneously reacts with 4‐hydroxycoumarins to afford the α,β‐unsaturated esters instead of Wittig olefination. Subsequently, these α,β‐unsaturated esters undergo a smooth Friedel‐Crafts type cyclization with arenes in the presence of AlCl3 to give a new series of 2,3‐diarylindanones in good to excellent yields. Additionally, the reduction of α,β‐unsaturated esters with NaBH4 followed by the acid catalyzed cyclization of resulting allylic alcohols afforded the 2‐arylindenes in good yields. This is the first report on the use of α,β‐unsaturated esters as precursors for diarylindanones and arylindenes synthesis.