To a suspension of 0.53 g sodium hydride (50%) in 50 ml DMF was added 2.40 g dioxobenzoxazine from part (a). After 15 min. 1.20 g ethyl bromide was added and the mixture was stirred overnight at room temperature. Sodium hydride (1.06 g) was then added followed by 3.52 g diethyl malonate dropwise. The reaction mixture was heated on a steam bath for 2 hrs., then poured into dilute acetic acid and concentrated in vacuo. The residue was chromatographed on silica gel to give 1.35 g ethyl 1-ethyl-1,4-dihydro-2-hydroxy-4-oxo-7-(4-pyridinyl)-3quinolinecarboxylate used directly in the next reaction. A sample of the compound upon further purification was obtained as a yellow powder, m.p. 153-157° C.
