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

Abstract

AbstractThe reactions of 1‐p‐methoxyphenyl‐2‐methylpropen‐1‐yl trifluoroacetate (I–OCOCF3) 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 AnCOCHMe2 (III) in a second order reaction with five amines and with CF3 CH2 ONa, and I–OCOCF3 gives a second order reaction with 2,6‐lutidine. In AcOH/NaOAc, I–OCOCF3 gives the corresponding acetate I–OAc, and I–ODNB gives I–OAc and III. The kAcOH/kAcOD 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 CF3 CH2O− (formed from the amine and TFE) on the carbonyl of the ester group in a BAC2 mechanism. In AcOH, an electrophilic addition‐elimination mechanism (AdE–E) for the reaction of I–OCOCF3 is supported by the solvent isotope effect. The solvent isotope effect and the products from I–ODNB in AcOH are consistent with an SN1 mechanism, but since the kCl/kODNB ratio is lower than that in saturated systems, an AAC2 mechanism cannot be unequivocally excluded. The effect of the leaving group in the vinylic SN1 reaction is discussed.