Total synthesis of (±)-β-chamigrene and (±)-laurencenone C via Ireland ester Claisen rearrangement and an intramolecular type II carbonyl ene reaction sequence

A combination of Ireland ester Claisen rearrangement and intramolecular type II carbonyl ene reactions were exploited for the total synthesis of chamigrenes containing a quaternary carbon atom next to the spirocentre in spiro[5.5]undecane.