A mixture of (S)-methyl 5-cyclobutoxy-2-methyl-6-(1H-pyrazol-4-yl)-3,4-dihydroquinoline-1(2H)-carboxylate (0.160 g, 0.47 mmol), 1,1-dioxidotetrahydro-2H-thiopyran-4-yl methanesulfonate (0.320 g, 1.40 mmol) and cesium carbonate (0.457 g, 1.40 mmol) in N,N-dimethylformamide (5 mL) stirred overnight at 110° C. The reaction mixture was cooled to room temperature, diluted with water (20 mL), and extracted with ethyl acetate (3×10 mL). The combined organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated under vacuum. The residue was purified by preparative thin layer chromatography (eluting with 50% ethyl acetate/petroleum ether). The product was further purified by preparative-HPLC with the following conditions (Waters I): Column, Xbridge RP18 5 um, 19×150 mm; Mobile phase, water (0.05% ammonium bicarbonate) and acetonitrile (40% to 80% acetonitrile in 10 min; flow rate: 20 mL/min); Detector, UV 220&254 nm. This afforded of methyl (2S)-5-cyclobutoxy-6-[1-(1,1-dioxo-1λ6-thian-4-yl)-1H-pyrazol-4-yl]-2-methyl-1,2,3,4-tetrahydroquinoline-1-carboxylate (0.040 g, 18%) as a white solid. 1H NMR (400 MHz, CD3OD) δ ppm 1.18 (d, J=6.40 Hz, 3H), 1.29-1.31 (m, 1H), 1.47-1.49 (m, 1H), 1.60-1.62 (m, 1H), 2.01-2.08 (m, 4H), 2.11-2.24 (m, 1H), 2.45-2.47 (m, 1H), 2.63-2.68 (m, 4H), 2.90-2.94 (m, 1H), 3.10-3.17 (m, 2H), 3.45-3.47 (m, 2H), 3.78 (s, 3H), 4.06-1.10 (m, 1H), 4.45-4.58 (m, 2H), 7.22 (d, J=8.40 Hz, 1H), 7.31 (d, J=8.40 Hz, 1H), 7.81 (s, 2H). MS (ESI, pos. ion) m/z 474 [M+H]+.
