Synthesis of 1,1,4,5-Tetrasubstituted Phthalans via Pd-Catalyzed Three-Component Reactions of Haloarenes, Alkynes, and Protic Nucleophiles

A novel approach for the synthesis of 1,1,4,5-tetrasubstituted phthalans is developed via a tandem palladium-catalyzed Sonogashira coupling/propargyl-allenyl isomerization/ pentadehydro-Diels-Alder cyclization/regioselective nucleophilic addition sequence. The reaction shows good functional tolerance and provides a wide variety of substituted phthalans in moderate to high yields from haloarenes, triynes, and protic nucleophiles, such as amines and alcohols, under very mild conditions.