fig2

Figure 2. Condition optimization. Conditions: 1a (0.1 mmol), 2a (0.2 mmol), Pd₂(dba)₃·CHCl₃ (5 mol%) and chiral ligand (20 mol%) in 2.0 mL anhydrous DCM at rt under the irradiation of 6 W blue LEDs for 24 h. ^aDetermined by analyzing the ¹H NMR of reaction mixture with 1,3,5-trimethoxybenzene as an internal standard. ^bDetermined by chiral HPLC analysis of the purified products. ^cDetermined by ¹H NMR analysis of the reaction mixture. ^dLigand (10 mol%) was used instead. ^eIsolated yield. dba: Dibenzylideneacetone; rt: room temperature; LEDs: light-emitting diodes; dr: diastereoisomer ratio; ee: enantiomer excess; DCM: dichloromethane; ND: not detected; DMF: N,N-dimethylformamide; THF: tetrahydrofuran; NMR: nuclear magnetic resonance; HPLC: high performance liquid chromatography.