Reaction Steps
A mixture of 6-bromoquinoline (8, 2.63 g, 12.6 mmol), propargylaldehyde diethyl acetal (3.73 mL, 25.2 mmol, 2.0 equiv), triethylamine (TEA, 12.7 mL, 90.8 mmol, 7.2 equiv), copper(I) iodide (CuI, 24.0 mg, 0.126 mmol, 0.01 equiv), and triphenylphosphine (PPh3, 0.39716 g, 1.5142 mmol, 0.12 equiv) in N,N-dimethylformamide (DMF, 15.6 mL, 202 mmol) was degassed with nitrogen bubbling for 5 min. Palladium acetate (Pd(OAc)2, 0.08499 g, 0.3786 mmol, 0.03 equiv) was added and the mixture was degassed with nitrogen bubbling for 5 min. The reaction mixture was heated to 90° C. under nitrogen with stirring. After 3 h and 10 min, HPLC indicated that the reaction was complete. The reaction mixture was diluted with ethyl acetate (EtOAc, 100 mL) and washed with water (H2O, 2×100 mL). The aqueous layer was extracted with ethyl acetate (EtOAc, 20 mL). The combined organic extracts were then concentrated under the reduced pressure to give the crude product as a black oil. The crude product was purified by flash column chromatography (SiO2, 0-40% EtOAc in hexane gradient elution) to afford 6-(3,3-diethoxyprop-1-ynyl)quinoline (22, 3.2 g, 3.22 g theoretical, 99% yield) as a colorless oil. For 22: 1H NMR (400 MHz, DMSO-d6) δ ppm 8.92 (dd, 1H, J=4.35 Hz, 1.86 Hz), 8.36 (d, 1H, J=8.40 Hz, 1.66 Hz), 8.20 (d, 1H, J=1.78 Hz), 7.99 (d, 1H, J=8.71 Hz), 7.76 (dd, 1H, J=8.71 Hz, 1.87 Hz), 7.57 (dd, 1H, J=8.09 Hz, 4.05 Hz), 5.58 (s, 1H), 3.75-3.55 (m, 4H), 1.17 (t, 6H), J=7.16 Hz); C16H17NO2 (MW 255.31), LCMS (EI) m/e 256.0 (M++H).
