Asymmetric Induction in Ruthenium‐Catalyzed [2+2] Cycloadditions between Bicyclic Alkenes and a Chiral Acetylenic Acyl Sultam

Cyclobutene tricyclic products were isolated in good yields (44–99 %) from Ru-catalyzed [2+2] cycloadditions between bicyclic alkenes and a chiral acetylenic acyl sultam (see scheme). The cycloadditions occurred with high stereoselectivity (only exo cycloadducts were formed) and high levels of asymmetric induction (67–98.8 % ee after removal of the chiral auxiliary). X=H, CH2OMe, Br; X–X=Ar; Y=CH2, O, CHPh; Cp*=1,2,3,4,5-pentamethylcyclopentadiene; COD=1,5-cyclooctadiene.