Bifunctional copper catalysts. Part II. Stereoselective synthesis of (-)-menthol starting from (+)-citronellal

The one-step transformation of (+)-citronellal into (-)-menthol has been realised with yield ∼90% and stereoselectivity up to 80% under mild conditions in the presence of Cu/SiO2 by exploiting the presence of acidic and hydrogenation sites on the catalyst surface, the unusual reducibility of an olefinic bond under these conditions and the chemoselectivity of the process.