Exalted Resonance Demands in the Substituent Effects on the Acetolyses of 2-Arylethyl Trifluoromethanesulfonates Destabilized by CN and CF3 Groups

Substituent effects on the acetolysis rates of 2-aryl-l-cyano-l-(trifluoromethyl)ethyl trifluoromethanesulfonates (α-OTf) and 2-aryl-2-cyano-2-(trifluoromethyl)ethyl trifluoromethanesulfonates (β-OTf) were investigated by using LArSR equation. The obtained p and r + values were p = -3.28, r + = 0.98 and p = -3.48, r + = 0.93 for the acetolysis of α-OTf and β-OTf, respectively. The obtained p values are comparable to those for typical aryl-assisted solvolyses, but the r + values are much larger. The large r + values suggest that the ester bond cleavages in the deactivated aryl-assisted solvolyses are assisted by the strong participation of the β-aryl group.