2.4 General experimental procedure for the Knoevenagel reaction (1a-k→2a–k)
A 5 mL microcentrifuge tube, was charged with solvent (2 mL), to which the 1a-k (50 mM) and 1,3-dicarbonyl compound (100 mM) were introduced. The resulting mixture was stirred for the specified amount of time at 25 ºC. After completion, the product was extracted into EtOAc (4×5 mL), The combined organic layers were dried over anhydrous Na2SO4 and evaporated under a vacuum. The residue was purified by flash column chromatography with petroleum ether and ethyl acetate to afford the desired products.