反应详情

5.18 g (0.02 mole) of 4-(3,5-dichloro-4-methylphenyl)-4-oxo-2-butenoic acid, prepared as described in Example 1(b), were suspended in 50 ml of methanol and the suspension was then saturated with dry hydrogen chloride gas by blowing the gas through the suspension whilst ice-cooling and stirring it. The resulting mixture was then stirred at room temperature for a further 2 hours, to give methyl 2-chloro-4-(3,5-dichloro-4-methylphenyl)-4-oxobutyrate. The resulting mixture was then heated under reflux for a further 2 hours to replace the chlorine substituent at the 2-position by a methoxy group. After completion of this reaction, methanol was distilled off and the residue was extracted with diethyl ether. The extract was washed with water and then dried over anhydrous sodium sulphate. The solvent was then distilled off, giving 5.93 g of a crude product, which was subjected to column chromatography through silica gel, eluted successively with benzene and then with a 20:1 by volume mixture of benzene and ethyl acetate, to give 4.46 g (yield 73.1%) of the desired methyl 4-(3,5-dichloro-4-methylphenyl)-2-methoxy-4-oxobutyrate, melting at 75°-78° C.

1. temperaturecooling
2. stirringThe resulting mixture was then stirred at room temperature for a further 2 hours