Ring enlargement through acyloin condensation of cycloalkane-1,2-dicarboxylic esters

Cycloalkane-1,2-dicarboxylic esters of 11-, 12-, and 13-membered rings were prepared from cyclododecanone. Acyloin condensation of these esters in the presence of trimethylchlorosilane followed by acidic hydrolysis afforded 13-, 14-, and 15-membered cycloalkane-1,2-diones in 71–74% yields. The diketones were reduced by treatment with triethyl phosphite and alkali hydroxide into corresponding acyloins.

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.