Synthesis of exaltone and dl-muscone based on 1,5,9-cyclododecatriene

Bicyclo[9•4•1]hexadecan-16-one is prepared from cyclododecanone via four steps: ethoxycarbonylation, condensation with 1,4-dibromobutane, saponification, and decarboxylation. Photolysis of the bicyclic ketone yields a ketene which is trapped with methanol to afford methyl cyclopentadecanecarboxylate or alternatively oxidized to exaltone directly. The ester is also converted into exaltone via five steps. dl-Muscone is prepared by applying the same scheme to cyclotridecanone with 14-methylbicyclo-[10•3•1]hexadecan-16-one as the key intermediate.