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

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. (C) 2020 Elsevier Ltd. All rights reserved.