An examination of β-enolization in benzobicyclo[2.2.2], [3.2.1], and [3.2.2] ketones

Abstract

Under homoenolization conditions (t-BuO−/t-BuOH/185 °C), the 3,3-dimethylbenzobicyclo[2.2.2]- and [3.2.1]octen-2-ones (7, 8) and their [3.2.2] homolog (9) each undergo β-enolate rearrangement to a single ketone. These rearrangement processes, however, are in competition with Haller–Bauer cleavage, in contrast to the behavior of bicyclo-[2.2.2]octenone, which is not cleaved under these reaction conditions, although Haller–Bauer cleavage was found as a minor process for the [3.2.1] and [3.2.2] analogs. The structures of all products were determined primarily from their 1H and 13C magnetic resonance spectra.