Substituent effects in the migration step of the Baeyer-Villiger rearrangement. A theoretical study.
Quantum mechanical calculations have been performed on the migration step of the Baeyer-Villiger (BV) rearrangements of some acetophenones, p-RC6H4COCH3 (R = CN, Cl, H, CH3, CH3O) with m-chloroperbenzoic acid. The energy barriers, charge distributions, and frontier molecular orbitals determined for the aryl migration step explain the effects of substituents on the reactivity of these ketones. A plot of the log of relative oxidation rates of the ketones versus their corresponding calculated energy barriers of the migration stage showed a downward deviation for the p-OCH3 derivative. This result is consistent with a change in the rate-determining step, from the aryl migration to the carbonyl addition, in the case of p-methoxyacetophenone, according to the suggestion that the rate-determining step of the BV oxidation can change with variations in the substituent group.
Reyes
Lino
L
Depto. de Química Orgánica, Facultad de Química, Universidad Nacional Autónoma de México, Del. Coyoacan, México, DF, C.P. 04510, México. linoj@correo.unam.mx
Castro
Miguel
M
Cruz
Julián
J
Rubio
Manuel
M