1,1′-Carbonyldiimidazole (0.44 g, 2.69 mmol) was added to a solution of 4-morpholinoaniline (0.40 g, 2.24 mmol) in THF (4 ml) followed by stirring for 2 hours with cooling on ice-bath. The reaction mixture was filtered and washed with diethyl ether. The filtrate was added to a solution of 2-hydroxymethyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazole (0.30 g, 1.62 mmol) in DMF (3 ml) with cooling on ice-bath. Then, cuprous chloride (75 mg, 0.76 mmol) was added to the resulting mixture followed by stirring at room temperature for 2 hours. Water was added to the reaction mixture, the resulting mixture was extracted with ethyl acetate, and the extract was washed with water, dried over magnesium sulfate, and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (methylene chloride/acetone=9/1), and washed with methylene chloride-ethyl acetate to afford 6-nitro-2,3-dihydroimidazo[2,1-b]oxazol-2-ylmethyl (4-morpholinophenyl)carbamate (34 mg, yield 5%) as a white solid.
