Exalted Resonance Demands in the Substituent Effects on the Acetolyses of 2-Arylethyl Trifluoromethanesulfonates Destabilized by CN and CF<sub>3</sub>Groups
作者:Satoshi Usui、Shoko Tsuboya、Yukihiro Umezawa、Ken Hazama、Mutsuo Okamura
DOI:10.1246/bcsj.82.254
日期:2009.2.15
Substituent effects on the acetolysis rates of 2-aryl-1-cyano-1-(trifluoromethyl)ethyl trifluoromethanesulfonates (α-OTf) and 2-aryl-2-cyano-2-(trifluoromethyl)ethyl trifluoromethanesulfonates (β-OTf) were investigated by using LArSR equation. The obtained ρ and r+ values were ρ = −3.28, r+ = 0.98 and ρ = −3.48, r+ = 0.93 for the acetolysis of α-OTf and β-OTf, respectively. The obtained ρ 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.
通过使用LArSR方程研究了2-芳基-1-氰基-1-(三氟甲基)乙基三氟甲烷磺酸酯(α-OTf)和2-芳基-2-氰基-2-(三氟甲基)乙基三氟甲烷磺酸酯(β-OTf)的醋酸解离速率的取代基效应。得到的ρ值和r+值分别为α-OTf的ρ = −3.28,r+ = 0.98,以及β-OTf的ρ = −3.48,r+ = 0.93。获得的ρ值与典型的芳基辅助的溶剂解离相当,但r+值要大得多。较大的r+值表明,在去活化的芳基辅助溶剂解离中,酯键的断裂得到了β-芳基团的强力参与的帮助。