Dichloromethane → ethyl 6,7-dimethoxy-2-methyl-4-oxo-3,4-dihydro-1(2H)-quinolinecarboxylate

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Reaction Steps

A mixture of 15 g. of the quinoline product of Example 4, 95 g. of potassium carbonate, and 225 ml. of methylene chloride was stirred for 1 hr., then 14.7 g. of ethyl chloroformate in 20 ml. of methylene chloride was added dropwise and the suspension was allowed to stir for 72 hrs. at room temperature. Additional 7.3 g. portions of ethyl chloroformate were added after 24 and 48 hrs. and 47 g. of potassium carbonate was added after 48 hrs. The reaction mixture was quenched with water and extracted several times with methylene chloride. The combined organic extracts were washed with water, dried over magnesium sulfate and concentrated under reduced pressure to give an oil which solidified upon standing; trituration with 5% ethyl acetate in hexane gave 17 g. of a solid, m.p. 112°-116°. This solid was chromatographed on silica gel, eluting with 1:1 ethyl acetate/hexane, and recrystallized from 1:1 ethyl acetate/hexane to give 13.9 g. of white crystals, m.p. 116.5°-18°.

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