Dimethylformamide → 4-Trifluromethylbenzyl 4-[2-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazole-2,4'-piperidin]-1'-yl)-2-oxoethyl]piperazine-1-carboxylate

Participants

Reaction Steps

Tert-butyl 4-[2-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazol-2,4′-piperidin]-1′-yl)-2-oxoethyl]piperazine-1-carboxylate prepared in Example 653 (300 mg, 0.67 mmol) was dissolved in methylene chloride (5 ml) To the solution, trifluoroacetic acid (5 ml) was added followed by stirring at room temperature for 6 hours. The reaction mixture was concentrated under reduced pressure. To the residue, methylene chloride (1 ml) and triethylamine (1 ml) were added. The reaction mixture was stirred at room temperature for 5 minutes and concentrated under reduced pressure, and the residue was dissolved in DMF (15 ml). To the solution, a mixture of 4-trifluoromethylbenzyl alcohol (293 mg, 1.67 mmol), 1,1′-carbonyldiimidazole (270 mg, 1.67 mmol) and DMF (5 ml) stirred at room temperature for 3 hours was added followed by stirring at room temperature overnight. The reaction mixture was poured into water and extracted with ethyl acetate, and the organic phase was washed with a saturated saline solution and dried over magnesium sulfate. After filtration, the resulting filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (methylene chloride/methanol=200/1) and crystallized from methylene chloride-isopropyl ether to afford 4-trifluromethylbenzyl 4-[2-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazole-2,4′-piperidin]-1′-yl)-2-oxoethyl]piperazine-1-carboxylate (324 mg, yield 88%) as a light pink powder.

Provenance & Evidence