Synthesis of bicyclo[2.2.2]oct-5-en-2-ones via a tandem intermolecular Michael addition intramolecular aldol process (a bridged Robinson annulation)

A novel one-pot synthesis of the several bicyclo[2.2.2]oct-5-en-2-ones 19 has been developed in which a cyclic or acyclic ketone 18 is reacted with a cyclic enone 6 in the presence of strong acid to give the bicyclic enone product 19. Alternatively, the intermediate diketone 21 can be prepared separately and subjected to the reaction conditions to give the bicyclic enones 19 in good yields.