Water → (E)-(5,6-dihydro-1,4,2-dioxazin-3-yl)(2-hydroxyphenyl)methanone O-methyloxime

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Reaction Steps

4.4 g (0.021 mol) of (5,6-dihydro-1,4,2-dioxazin-3-yl)-(2-hydroxy-phenyl)-methanone (III-1) and 1.87 g (0.022 mol) of O-methylhydroxylamine hydrochloride in 22 ml of dimethylformamide are heated to 100° C. for 2 hours. The reaction mixture is poured into water and the resulting mixture is extracted with ethyl acetate, the organic phase is dried over sodium sulphate and the solvent is distilled off under reduced pressure. 5.7 g of crude (5,6-dihydro-1,4,2-dioxazin-3-yl)-(2-hydroxy-phenyl)-methanone O-methyl-oxime (1) comprising 17.5% of the E isomer and 38% of the Z isomer by HPLC are obtained. This crude product is chromatographed over silica gel using a mixture of petroleum ether/tert-butyl methyl ether (1:1). 1.55 g of Z-(5,6-dihydro-1,4,2-dioxazin-3-yl)-(2-hydroxy-phenyl)-methanone O-methyl-oxime (1) of a purity of 91.5% (HPLC)=28.27% of theory) are obtained.

Provenance & Evidence