Improving and stabilizing fluorinated aryl borane catalysts for epoxide ring-opening

Epoxide ring-opening is a key reaction in organic chemistry. We have previously shown that B(C6F5)3, strongly Lewis acidic arylborane, exhibited high rates and unusual selectivities for catalyzing the of aliphatic epoxides with alcohols. Here we compare catalysts form B(C6H5?XFX)3 (x = 5, 4, 3, 0) determine moderately arylboranes higher regioselectivity, but slower this reaction. At temperatures, these can also hydrolyze into inactive species. However, deactivation suppressed presence co-catalytic amounts 1,2-propanediol, DFT calculations suggest role arylborane-H2O-diol complexes. Thermal stabilization regioselectivity enhancement by diol are both more pronounced B(C6F5)3 than less B(C6HF4)3 B(C6H2F3)3 catalysts. These results further demonstrate catalytic relevance H-bound networks diols enable their use at temperatures greatly increased rates.