Triethylamine → 1-(3-Fluorobenzoyl)pyrazolidin-3-one

To a solution of pyrazolidin-3-one (6.9 gm, 0.080 mmol, 1 equiv.) in dry dichloromethane (70 ml), 3-fluorobenzoic acid (12.3 gm, 0.088 mmol, 1.1 equiv.), triethylamine (24.3 gm, 0.240 mmol, 3 equiv.) and 1-propane phosphonic acid cyclic anhydride (60% by weight in ethyl acetate) (51 gm, 0.16 mmol, 2 equiv.) were added in cooling condition and stirred for overnight at room temperature. The reaction mixture was concentrated and the residue was poured in water (500 ml), extracted with dichloromethane (100 ml×2) and concentrated. The crude product was purified by silica gel column using (60-120) mesh to get the pure product as yellow oil (5.4 gm, 32% yield).