Fig. 3: Substrate scope.

^aConducted with catalyst/substrate (0.2 mmol) ratio of 1: 50 in 1 mL of solvent, HCO₂H (2.0 equiv.)/Et₃N (2 mol%) for syn–isomer 3 and HCO₂H/Et₃N azeotropic mixture (20 μL) obtained anti–isomer 2. Isolated yield including the minor enantiomer, the ee and dr value of were determined by HPLC analysis using a chiral stationary phase. ^b(S,S)-cat.6 (5 mol%) and HCO₂H/Et₃N azeotropic mixture (50 μL) were used. ^c(S,S)-cat.6 (5 mol%) and HCO₂H (2.0 equiv.) were used for 24 h. ^d(S,S)-cat.6 (1 mol%) and HCO₂H/Et₃N azeotropic mixture (20 μL) were used for 1 h. ^e(S,S)-cat.6 (1 mol%) and HCO₂H/Et₃N azeotropic mixture (20 μL) were used for 0.5 h. ^f(S,S)-cat.6 (5 mol%) and HCO₂H/Et₃N azeotropic mixture (40 μL) were used for 24 h.