Ring Closing Metathesis Directed Synthesis of (R)-(−)-Muscone from (+)-Citronellal

A concise and simple synthesis of the valuable perfumery ingredient (R)-(−)-muscone 1 has been achieved through ring closing olefin metathesis (RCM) aided macrocyclization protocol as the key step. Commercially available starting material (R)-(+)-citronellal 3 has been employed as a building unit in preparing the acyclic diolefinic substrate 16, which in turn was exposed to bis(tricyclohexylphosphine)benzylideneruthenium dichloride catalyst 2 to afford the cyclic RCM reaction product 17 in 78% yield. Catalytic hydrogenation of 17 furnished enantiomerically pure (R)-(−)-muscone 1.