fig2
Figure 2. Optimized conditions[a]. [a] Standard condition: 1a (0.1 mmol), 2a (1.2 equiv), NHC.HX (10 mol%), solvent (0.1 M), 30 °C, and 24 h, then SiO2, 70 °C, and 10 h; [b] Yield of the product 3a after column chromatography; [c] Determined via 1H NMR spectroscopy; [d] Determined by chiral HPLC, % ee = (R-S) / (R + S) * 100.
