ethyl 2-(N-methyleneamino)-2-methylpropanoate → ethyl [5-(2-fluorophenyl)-2,3-dihydro-6-methyl-4-oxo-4H-1,3-oxazin-3-yl]-2-methylpropanoate

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A mixture of 5-(2-fluorophenyl)-2,2-dimethyl-6-methyl-4H-1,3-dioxin-4-one (2.0 g) and ethyl 2-(N-methyleneamino)-2-methylpropionate (1.45 g) was heated under reflux in xylene for 10 hours. After evaporation to dryness the residue was purified by dry column chromatography on silica gel eluting with cyclohexane/ethyl acetate to give ethyl [5-(2-fluorophenyl)-2,3-dihydro-6-methyl-4-oxo-4H-1,3-oxazin-3-yl]-2-methylpropanoate as a pale yellow oil (1.7 g), NMR 1.24(t,3H), 1.42(s,6H), 1.57(s,3H), 4.15(q,2H), 5.3(s,2H), 7. 74(m,4H).

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