Scheme 4. Scope of the aldehyde component. a Reaction conditions: 1 (0.2 mmol), Ru(bpy)3Cl2·6H2O (2 mol%), Cu(OAc)2·H2O (5 mol%), CH3CN (3 mL), 5 W blue LEDs light irradiation under air at room temperature for 2 h, then, A (10 mol%) and 2 (0.6 mmol) were added. Yield is that of the product isolated by flash column chromatography on silica gel. The ee and dr were determined by HPLC. b Cu(OTf)2 (5 mol%) was used instead of Cu(OAc)2·H2O.
