Stereoselective Ring-Opening Hydrofluorination of Aryl Epoxides

Davies et al. have reported a stereoselective ring-opening hydrofluorination of aryl epoxides with 0.33 equiv of BF₃•OEt₂ at 20 °C to give rapidly the corresponding syn-fluorohydrins (> 99:1 dr). Mechanistic evidence suggested that a stereoselective S_N1-type epoxide ring-opening process involving coordination of BF₃ to the oxirane oxygen and transferring of fluorine.