Regioselective Reversal in One-Pot and Two-Step Reaction of 1‑(2-Hydroxyphenyl)-Propargyl Alcohols with Aryl/Alkyl Mercaptan: Construction of 3‑(Alkylthio)benzofurans and 2‑(Alkylthiomethyl)benzofurans Starting from Identical Materials

The Cu(MeCN)₄PF₆-catalyzed reaction of 1-(2-hydroxyphenyl)-propargyl alcohols with aryl/alkyl mercaptan and subsequent treatment with K₂CO₃ only offered 3-(alkylthio)benzofurans, whereas the stoichiometric-exceeding CuI-mediated reaction and subsequent treatment with DIPEA furnished 2-(alkylthiomethyl)benzofurans with high selectivity. The amount of Cu(I) salts plays a key role in selective formation. This unique protocol for the selective construction of the two series of benzofurans containing alkylthio group proved to be suitable for broad substrates 1 and 2 except for aliphatic alkynyl alcohols.