Flexible Synthesis of Benzofuranones from ortho-Alkynyl Phenols or Benzofurans

Graphical Two flexible methods for synthesizing benzofuran-3(2H)-ones are developed, with easily available starting materials, good chemoselectivity, and very mild conditions. One protocol for benzofuranone is a gold-catalyzed cycloisomerization of o -alkynyl phenol with alcohol or acid. Another metal-free synthesis of benzofuranone is the treatment of benzofuran with alcohol, acid, or H 2 O. Benzofuranones are attractive synthetic targets in medicinal and natural products. The cycloisomerization of o -alkynyl phenol to benzofuran-3(2H)-one is reported here using gold(I) and Selectfluor. This benzofuranone can also be obtained from benzofuran without a gold catalyst. This study presents two appealing synthetic methods for benzofuran-3(2H)-ones that use readily available starting materials, have high chemoselectivity and operate under very mild conditions.