Radical cascade cyclization for synthesizing 3,4-fused tricyclic benzofuran derivatives

Abstract A new method for synthesizing 3,4-fused tricyclic 3-alkylidene dihydrobenzofuran derivatives was developed. Treatment of propargyl iodophenol derivatives with a tethered alkene at the three contiguous positions under the radical cascade reaction conditions induced the reaction of the generated vinyl radical intermediates with the internal alkene, producing tricyclic 3-alkylidene dihydrobenzofurans in 25%–93% yield. The reaction products could be utilized as the precursors for 3,4-fused tricyclic benzofurans.