A mixture of 2-(3-bromo-phenyl)-3,3-dimethyl-1,2,3,4-tetrahydro-quinoline-6-carboxylic acid (500 mg, 1.4 mmol), 1-methyl-piperazine-2,3-dione (267 mg, 2.1 mmol), copper(I) iodide (80 mg, 0.4 mmol), N,N-dimethylglycine hydrochloride (117 mg, 0.8 mmol) and potassium carbonate (769 mg, 5.6 mmol) in dimethyl sulfoxide (5 mL) was stirred at 120° C. for 16 h. Then the reaction mixture cooled to room temperature. The reaction mixture was extracted with ethyl acetate (2×150 mL), washed with water (2×50 mL) and saturated aqueous ammonium chloride solution (2×50 mL), dried over anhydrous sodium sulfate and then concentrated in vacuo. Purification by Waters automated flash system (column: Xterra 30 mm×100 mm, sample manager 2767, pump 2525, detector: ZQ mass and UV 2487, solvent system: acetonitrile and 0.1% ammonium hydroxide in water) afforded 3,3-dimethyl-2-[3-(4-methyl-2,3-dioxo-piperazin-1-yl)-phenyl]-1,2,3,4-tetrahydro-quinoline-6-carboxylic acid (456 mg, 80%) as a white solid: LC/MS m/e calcd for C23H25N3O4 (M+H)+: 408.47, observed: 408.1.
