Acid-catalysed cleavage of the cyclopropane ring in some ketones of the carane series

Abstract

Cleavage of the cyclopropane ring of (–)-cis-caran-4-one (III) in the presence of dry hydrogen bromide in acetic acid solution occurs without preference at C(6)–C(7) and C(1)–C(7). In contrast, in (–)-cis-caran-2-one (XII) and (–)-trans-caran-2-one (XIII) only cleavage of the C(1)–C(7) bond is observed. The results are discussed. Absolute configurations of (–)-(XII) and (–)-(XIII) are supported by the products from cyclopropane ring opening.

Synthesis of (±)-cis-m-menthan-6-one (V) is reported.