Synthesis of 4‐Formyl‐2‐arylbenzofuran Derivatives by PdCl(C3H5)dppb‐Catalyzed Tandem Sonogashira Coupling‐Cyclization under Microwave Irradiation ‐ Application to the Synthesis of Viniferifuran Analogues

Herein we present the use of low catalyst loading of PdCl(C3H5)dppb (1 mol%) to directly prepare 4‐CHO‐2‐arylbenzofurans by copper‐free tandem Sonogashira coupling‐cyclization under microwave irradiation. The method was utilized to prepare highly substituted analogues of viniferifuran, a biologically active resveratrol dimer. Key transformations included the application of PdCl(C3H5)dppb (5 mol%) catalyzed direct arylation of C‐3 sterically congested C‐2 and C‐4 substituted benzofuran substrates. Finally, we demonstrated that BCl3/TBAI is superior to BBr3 for final demethylation. An improved method for the synthesis of 4‐formyl‐2‐arylbenzofuran derivatives is described using tandem Sonogashira‐cyclization on ortho‐halophenol derivatives catalyzed by PdCl(C3H5)dppb. Further applications included the direct PdCl(C3H5)dppb catalyzed C‐3 arylation of benzofurans and the synthesis of polyphenolic analogues of viniferifuran.