Practical, Modular, and General Synthesis of Benzofurans through Extended Pummerer Annulation/Cross-Coupling Strategy

摘要

Operationally simple, efficient, and widely applicable Pummerer annulations of simple phenols with ketene dithioacetal monoxides, with the aid of trifluoroacetic anhydride, have been shown to provide a variety of benzofurans having a methylthio group at the 2-position. Subsequent and newly developed nickel-catalyzed arylation at the methylthio group culminates in diversity-oriented synthesis of multisub-stituted benzofurans. Our extended Pummerer annulation/ cross-coupling sequence is powerful enough to synthesize biologically active natural products as well as highly fluorescent benzofuran derivatives.