Trifluoroacetic anhydride → 6,7-dihydro-4H-[1,2,3]oxadiazolo[4,3-c][1,4]oxazin-8-ium-3-olate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

The crude 4-nitrosomorpholine-3-carboxylic acid (11.0 g) from step 1 was dissolved in THF (250 ml) and cooled to 0° C. A solution of trifluoroacetic anhydride (7.4 ml, 52 mmol) in THF (20 ml) was added with stirring over 10 min. The resulting mixture was stirred at 0° C. for 5 hr, and warmed to room temperature for 16 hr. The solvent was evaporated and the residue was diluted with 250 ml of ethyl acetate and stirred with 30 g of anhydrous potassium carbonate. The mixture was filtered through a pad of silica gel and the filtrate evaporated. The residue was washed with a mixture of ethyl acetate-ether to give 3.80 g of a white solid; mp 132–133° C.; MS (ESI) m/z 143.1 (M+H).

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