反应详情

A mixture of methyl 3-cyclopropyl-3-oxo-2-phenylpropanoate (6.54 g) and ethyl 2-(N-methyleneamino)-2-methylpropanoate was heated under reflux in xylene in the presence of 5A molecular sieve (33 g) for 7 hours. The mixture was evaporated and purified by chromatography on silica gel, eluting with hexane/ethyl acetate (7:3) to give ethyl 2-(6-cyclopropyl-2,3-dihydro-4-oxo-5-phenyl-4H-1,3-oxazin-3-yl)-2-methylpropanoate (7.56 g), as an oil, NMR (CDCl3)δ 0.7-0.78(m,2H), 0.95-1.01(m,2H), 1.22(t,3H), 1.54(s,6H), 1.52-1.61(m,1H), 4.14(q,2H), 5.17(s,2H), 7.21-7.42(m,5H).

1. temperaturewas heated
2. customThe mixture was evaporated
3. custompurified by chromatography on silica gel
4. washeluting with hexane/ethyl acetate (7:3)