Water → 3-[7-fluoro-4-propargyl-2H-1,4-benzoxazin-3(4H)-on-6-yl]-5-isopropylidene-1,3-oxazolidin-2,4-dione

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Reaction Steps

To a solution of 7-fluoro-6-isocyanato-4-propargyl-2H-1,4-benzoxazin-3(4H)-one (2.5 g) and methyl 2-hydroxy-3-methyl-3-butenoate (1.3 g) in benzene (50 ml), DBU (1.5 g) was added at room temperature. The resulting mixture was refluxed for 10 hours, cooled to room temperature, combined with water and extracted with ethyl acetate. The organic layer was washed with water, dried over magnesium sulfate and concentrated. The residue was purified by silica gel column chromatography using a mixture of toluene and ethyl acetate as the eluent to give Compound No. 9 (3.0 g).

Provenance & Evidence