Solvolysis of 1‐ p ‐Methoxyphenyl‐2‐Methylpropen‐1‐Yl Trifluoroacetate and 3,5‐Dinitrobenzoate

The reactions of 1‐ p ‐methoxyphenyl‐2‐methylpropen‐1‐yl trifluoroacetate (I–OCOCF 3 ) and 3,5‐dinitrobenzoate (I–ODNB) in AcOH/NaOAc or with amines in 2,2,2‐trifluoroethanol (TFE) were investigated. In TFE, I–ODNB gives trifluoroethyl 3,5‐dinitrobenzoate (II) and the ketone AnCOCHMe 2 (III) in a second order reaction with five amines and with CF 3 CH 2 ONa, and I–OCOCF 3 gives a second order reaction with 2,6‐lutidine. In AcOH/NaOAc, I–OCOCF 3 gives the corresponding acetate I–OAc, and I–ODNB gives I–OAc and III. The k AcOH /k AcOD values are 5.5–6.2 for I–OCOCF, and 1.03 ± 0.05 for I–ODNB. It is suggested that the rate determining step in TFE is the attack of CF 3 CH 2 O − (formed from the amine and TFE) on the carbonyl of the ester group in a B AC 2 mechanism. In AcOH, an electrophilic addition‐elimination mechanism (Ad E –E) for the reaction of I–OCOCF 3 is supported by the solvent isotope effect. The solvent isotope effect and the products from I–ODNB in AcOH are consistent with an S N 1 mechanism, but since the k Cl /k ODNB ratio is lower than that in saturated systems, an A AC 2 mechanism cannot be unequivocally excluded. The effect of the leaving group in the vinylic S N 1 reaction is discussed.