Use of the Ketal Claisen Rearrangement for the Synthesis of Cyclic Sesquiterpenes Containing Quaternary Centers. A Formal Synthesis of Cuparene.

Article abstract of DOI:10.1016/S0040-4020(01)89978-6

We have shown that the ketal based Claisen rearrangement can be useful for generating vicinal quaternary and tertiary-quaternary centers by suitable substitution on the reacting 2-cyclohexenols and cycloalkanone ketal.A rapid and efficient method for preparing hindered cycloalkanone ketals in very pure form is presented, as well as a useful modification for synthesizing the requied 2-cyclohexenols from alkyl anisoles with a minimum number of undesired side products.