Ethyl 1,4‐dihydro‐4‐oxo‐3‐quinolinecarboxylates by a tandem addition‐elimination‐SNAr reaction

Abstract The ethyl 1,4‐dihydro‐4‐oxo‐3‐quinolinecarboxylate ring structure, important in several drug compounds, has been prepared in two steps from ethyl 2‐(2‐fluorobenzoyl)acetate. Treatment of this β‐ketoester with N , N ‐dimethylformamide dimethyl acetal gives a 97% yield of the 2‐dimethylaminomethylene derivative. Reaction of this β‐enaminone with primary amines in N , N ‐dimethylformamide at 140°C for 48 h then affords the 1,4‐dihydro‐4‐oxo‐3‐quinolinecarboxylate esters in 60–74% yields by a tandem addition‐elimination‐S N Ar reaction. The synthesis of the starting material as well as procedural details and a mechanistic scenario are presented. J. Heterocyclic Chem., (2011).