Enantioselective Ir-Catalyzed Hydrogenation of Terminal Homoallyl Sulfones: Total Synthesis of (-)-Curcumene.

A novel methodology for the preparation of chiral methyl benzylic compounds is reported. Terminal homoallyl sulfones were prepared from homoallyl alcohols, which are easily accessible through the recently reported Lewis acid isomerization of oxetanes. The iridium-catalyzed asymmetric hydrogenation of homoallylic sulfones afforded γ-chiral sulfones with excellent enantioselectivities (up to 98% ee). The synthetic potential of this novel methodology was demonstrated by the total synthesis of ( R )-(-)-curcumene.