3.3. Deuterium Labeling Experiments

1,3-butadiynamide 1a (48 mg, 0.10 mmol), tetrakis(triphenylphosphine)palladium(0) (12 mg, 0.01 mmol, 10 mol%) and t-BuOK (28 mg, 0.25 mmol, 2.5 equiv) were introduced in a dry Schlenk tube under argon atmosphere. Then CD₃OD (0.75 mL) was added. The Schlenk tube was sealed and immediately placed in an oil bath preheated to 70 °C. After 30 min, the reaction mixture was diluted with EtOAc and washed with brine. After drying (MgSO₄), the organic layer was filtered and evaporated under reduced pressure. The product was purified via column chromatography (SiO₂ pretreated with n-pentane/Et₂O/Et₃N 94:2:2 (v/v/v), n-pentane/Et₂O 98:2 to 95:5 (v/v)) to yield 8a as an oil (13.5 mg, 0.058 mmol, yield: 58%). R_f = 0.72 (n-pentane/Et₂O 10:1 (v/v)).

D₅-2-Methoxy-4-(pent-1-en-1-yl)quinoline (8a). ¹H NMR (500 MHz, CDCl₃) δ 7.98 (dd, ³J = 8.3 Hz, ⁴J = 1.0 Hz, 1 H, H₅), 7.90 (m, 1 H, H₈), 7.62 (ddd, ³J = 8.3 Hz, ³J = 7.0 Hz, ⁴J = 1.2 Hz, 1 H, H₇), 7.39 (ddd, ³J = 8.1 Hz, ³J = 7.0 Hz, ⁴J = 1.0 Hz, 1 H, H₆), 6.42 (tt, ³J = 7.0 Hz, ³J = 2 Hz, 1 H, H₁₂), 2.32 (q_app, ³J = 7.2 Hz, 2 H, H₁₃), 1.57 (sext, ³J = 7.4 Hz, 2 H, H₁₄) and 1.00 (t, ³J = 7.4 Hz, 3 H, H₁₅). HRMS (ESI+): Calc’d for C₁₅H₁₃D₅NO [M + H]⁺: 233.1702; found: 233.1704.