The non-dimerizing orthoquinone monoketal, 6-acetoxy-6-methoxy-3- methoxycarbonylcyclohexa-2,4-dienone, conveniently prepared from oxidative acetoxylation of its parent phenol with PhI(OAc)2 in CH2Cl2-AcOH (3:1), cleanly undergoes 1,3-acetoxy migrations in the presence of silica gel at room temperature to furnish a 60:40 product mixture conceivably derived from [3,5] and [3,3] sigmatropic rearrangements. Density functional theory calculations indicate that the [3,5] shift is pseudopericyclic, has a remarkably low activation energy of 20.1 kcal/mol, and is favored by 5.4 kcal/mol over the pericyclic [3,3] shift, in qualitative agreement with the experimental observations.
|Number of pages||4|
|State||Published - Jan 22 1999|
- Quinonoid compounds