Trifluoroacetic acid → 2-[4-(Benzoxazol-2-yl)piperazin-1-yl]-1-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazole-2,4'-piperidin]-1'-yl)ethanone

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Reaction Steps

Tert-butyl 4-[2-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazole-2,4′-piperidine]-1′-yl)-2-oxoethyl]piperazine-1-carboxylate prepared in Example 653 (227 mg, 0.50 mmol) was dissolved in methylene chloride (5 ml). To the solution, trifluoroacetic acid (5 ml) was added followed by stirring at room temperature for 4 hours. The reaction mixture was concentrated under reduced pressure. To the residue, methylene chloride (1 ml) and triethylamine (1 ml) were added followed by stirring at room temperature for 5 minutes, and then the solution was concentrated under reduced pressure. The residue was dissolved in DMF (5 ml). To the solution, triethylamine (0.21 ml, 1.52 mmol) and 2-chlorobenzoxazole (86 μl, 0.76 mmol) were added followed by stirring at 80° C. for 2 hours. To the reaction mixture, water was added, and the mixture was extracted with methylene chloride. The organic phase was dried over magnesium sulfate and then filtered. The resulting filtrate was concentrated under reduced pressure. The residue was crystallized from methylene chloride-ethyl acetate to afford 2-[4-(benzoxazol-2-yl)piperazin-1-yl]-1-(2,3-dihydro-6-nitrospiro[imidazo[2,1-b]oxazole-2,4′-piperidin]-1′-yl)ethanone (99 mg, 42%) as a light yellow powder.

Provenance & Evidence