2,3-Benzofurandione, 2-[O-(2-hydroxyethyl)oxime] 3-(O-methyloxime) → (E)-(5,6-dihydro-1,4,2-dioxazin-3-yl)(2-hydroxyphenyl)methanone O-methyloxime

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Reaction Steps

2 g of benzofuran-2,3-dione 2-[O-(2-hydroxy-ethyl)-oxime] 3-(O-methyl-oxime) (II-1) (content according to HPLC analysis 96.88%, 0.0082 mol) prepared by the method of process e) are dissolved in 50 ml of diethyl ether saturated beforehand with hydrogen chloride gas at 0° C. Without further cooling, the mixture is stirred for 30 minutes, the solvent is then distilled off under reduced pressure and the residue is taken up once more in diethyl ether. Some of the product crystallizes out and is filtered off. The mother liquor is concentrated under reduced pressure and the residue is dissolved in 25 ml of diethyl ether saturated with hydrogen chloride gas at 0° C. Without further cooling, the solution is stirred for a further 30 minutes, the solvent is distilled off under reduced pressure and the residue is once more taken up in diethyl ether. A further fraction of the product crystallizes out and is likewise filtered off. In total, 1.37 g (69% of theory) of (5,6-dihydro-1,4,2-dioxazin-3-yl)-(2-hydroxy-phenyl)-methanone O-methyl-oxime (1) are obtained (content according to HPLC analysis: 97.59%).

Provenance & Evidence