1-prop-2-ynylpyrrole-2,5-dione

Conditions: temp:65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of maleic anhydride (19, 2.5 g, 25.5 mmol) and propargylamine (20, 1.75 mL, 25.5 mmol) in glacial acetic acid (50 mL) was stirred in the dark overnight. The reaction mixture was concentrated to dryness and the residue was recrystallized from a mixture of isopropyl alcohol and water. This gave 21 (3.079 g, 20.1 mmol, 79%) as white crystals. Compound 21 (1.49 g, 9.70 mmol) was suspended in acetic anhydride (7 mL) and sodium acetate (437 mg, 5.33 mmol) was added. The resulting suspension was stirred at 65° C. for 2 h, cooled down to room temperature, and then poured into ice-cold water (75 mL). The aqueous solution was extracted three times with diethyl ether. The combined organic layers were dried over Na2SO4, filtered, and concentrated. Column chromatography (CH2Cl2/EtOAc=1/1) provided 22 (755 mg, 5.59 mmol, 58%) as an off-white solid. 1H NMR (400 MHz, CDCl3) δ: 2.21 (t, 1H, J=2.6 Hz, ≡C—H), 4.30 (d, 2H, J=2.6 Hz, CH2), 6.76 (s, 2H, ═C—H). cooled down to room temperature The aqueous solution was extracted three times with diethyl ether The combined organic layers were dried over Na2SO4 filtered concentrated