Substituent effects on the reactions of aromatic triflones with para‐X‐anilines in methanol: Low intrinsic reactivity and transition state imbalances

Abstract

AbstractA kinetic study is reported for SNAr reactions of 2,4,6‐tris(trifluoromethanesulfonyl) anisole 1a with a series of para‐X‐substituted anilines 2a–e in a methanol solution at various temperatures. The substituent effects on free energy (Δ≠G), enthalpy (Δ≠H), and entropy (Δ≠S) of activation are examined. Aniline addition to triflone 1a is characterized by a βX=0.57, αZ=0.31, and an imbalance of I = αZ–βX=−0.26. The imbalance shows that resonance development lags behind CN bond formation at the transition state. Interestingly, analysis of the results in terms of Marcus theory reveals that these SNAr are associated with some extremely low intrinsic reactivity (log ko=−1.25& © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 255–262, 2011