Diethyl Ether → Diethyl 6-ethylamino-4-oxo-10-propyl-4H-pyrano[3,2-g]quinoline-2,8-dicarboxylate

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Reaction Steps

A mixture of the product of step (b) (2.2 g; 6.3953 mmoles) and diethyl oxalate (8.5 g; 58.2191 mole) in dry dimethylformamide (50 ml) was added slowly to a stirred suspension of ether washed sodium hydride (0.38 g, 15.83 mmole) under nitrogen. After the addition, the mixture was allowed to stir under nitrogen for 72 hours. The mixture was poured onto ice, followed by acidification with dilute hydrochloric acid. The pH of the mixture was adjusted to about 7 before extraction into ethyl acetate. The extract was washed with water, dried and evaporated to give a light yellow solid. The solid was dissolved in ethanolic hydrochloric acid and heated to reflux on a steambath for 3 hours. The mixture was cooled, and treated with water. This was then concentrated and the pH of the mixture was adjusted to about 7, followed by extraction with ethyl acetate. The extract was washed, dried and evaporated to give a brown solid (2 g; 74%). The solid was recrystallised from ethanol to give a light brown solid (1.5 g).

Provenance & Evidence