Diols Activation by Cu/Borinic Acids Synergistic Catalysis in Atroposelective Ring-Opening of Cyclic Diaryliodoniums.

A Cu-catalyzed enantioselective ring-opening alkoxygenation reaction of cyclic diaryliodonium salts and diols in the presence of borinic acids was reported. Tuning structure of borinic acids with six or five-membered ring skeleton could selectively activate 1,2-diols or 1,4-diols. A catalytic cycle through a key ion pair model that accounts for the observed enantioselectivity was proposed.