Synthesis of 3-Trifluoromethylbenzo[b]furans from Phenols via Direct Ortho Functionalization by Extended Pummerer Reaction

A concise and diversity-oriented route to trifluoromethylbenzo[b]furans has been devised. A variety of phenols are directly converted to the corresponding 2-methylthio-3-trifluoromethylbenzo[b]furans by new triflic-anhydride-mediated extended Pummerer annulation reactions with trifluoromethylketene dithioacetal monoxide. The methylthio group of the products undergoes further transformations, which increase the diversity of available trifluoromethylbenzo[b]furans.