After the reaction was complete, the reaction mixture was cooled, poured into saturated aq. NH4Cl (10 mL) and extracted with hexanes (3×6 mL). The combined organic extracts were washed with H2O (2×10 mL), brine (2×10 mL), dried over Na2SO4, and evaporated under reduced pressure. Crude residue was purified by flash column chromatography on silica gel using gradient EtOAchexane as eluent.