Into a 50-mL round-bottom flask, was placed a solution of 5-formyl-2,4-dimethylbenzoic acid (compound 151.3, 500 mg, 2.81 mmol) in DCM (10 mL) 4-(azetidin-3-yl)benzonitrile hydrochloride (compound 5.2, 545 mg, 2.80 mmol), DIEA (1.4 mL, 8.41 mmol) and HBTU (1.60 g, 4.22 mmol) were added. The reaction mixture was stirred for 3 h at room temperature. The reaction mixture was diluted with 150 mL of EtOAc, then washed with 2×50 mL of NH4Cl (sat.) and 1×50 mL of brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel chromatography with ethyl acetate/petroleum ether (1/1) as eluent to furnish 480 mg (54%) of the title compound as a white solid.
