Sequential Thermal and Catalyzed Claisen Rearrangements Toward the Synthesis of Thiocoumarin-Annulated Furopyrans

Regioselective synthesis of a hitherto unreported thiocoumarin-annulated furopyran moiety was achieved by the application of Claisen rearrangement in which a second Claisen rearrangement was achieved by anhydrous aluminum chloride. The precursor endocyclic compounds for catalyzed Claisen rearrangement were synthesized by the thermal [3,3] sigmatropic rearrangement of the corresponding ether.