Kinetics and Mechanism of Aminolysis of Aryl Cyclobutanecarboxylates in Acetonitrile.

The aminolysis of Z-aryl cyclobutanecarboxylates (II) with X-benzylamines is investigated in acetonitrile at 55.0 °C. The rates are uniformly greater by 2.2 times than the corresponding rates of aryl cyclopropanecarboxylates (III). All the selectivity parameters, ρX (βX), ρZ (βZ) and ρXZ, are quite similar for the two substrates II and III. The kH/kD values involving deuterated benzylamines (XC6H4CH2ND2) are greater than unity, but are marginally smaller than those for the reactions of III. Low ΔH‡ and large negative ΔS‡ values are obtained and adherence to the reactivity–selectivity principle is observed. All these results are consistent with a stepwise mechanism with rate-limiting expulsion of a leaving group (aryl oxides) from a tetrahedral intermediate, T±, with a hydrogen-bonded, four-center transition state.