Earth Abundant Metal-Catalyzed Intermolecular Dearomatization of Benzofurans and Indoles

A method to cyclopropanate benzofurans and Cbz-protected indoles using a Cu(II) catalyst has been developed. Aryl di-azoacetates react suitably with copper (II) hexafluoroacetoacetate (Cu(II)hfacac2) to form a putative metal carbenoid that gives a productive dearomative reaction with substituted benzofurans and Cbz-protected indoles. The use of Cu(II) rep-resents a shift toward more sustainable earth-abundant metal catalysts relative to the more common Rh(II)-based cata-lysts in Buchner cyclopropanations. This work serves as a foundation for further investigation into the use of earth-abundant metals for dearomative chemistry.