Hydrochloric Acid → 2-Methyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazol-2-ylmethyl piperidine-1-carboxylate

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Reaction Steps

Pyridine (0.37 ml, 4.5 mmol) and triphosgene (0.18 g, 0.6 mmol) were added to a suspension of 2-hydroxymethyl-2-methyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazole prepared in Example 33 (0.3 g, 1.5 mmol) in methylene chloride (15 ml) with cooling on ice-bath followed by stirring at room temperature for 2 hours. The reaction mixture was cooled on ice-bath and added piperidine (0.16 ml, 1.7 mmol). The resulting mixture was stirred at room temperature for 3 hours. The reaction mixture was cooled on ice-bath and added 10% hydrochloric acid, and the insoluble matters were removed by filtration. The filtrate was extracted with methylene chloride, and the organic phase was dried over magnesium sulfate and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (n-hexane/ethyl acetate=3/2) and recrystallized from methylene chloride-diisopropyl ether to afford 2-methyl-6-nitro-2,3-dihydroimidazo[2,1-b]oxazol-2-ylmethyl piperidine-1-carboxylate (65 mg, yield 14%) as a white solid.

Provenance & Evidence