反应详情

To a solution of (R)-4-(hex-3-ynyl)-2,2-dimethyl-1,3-dioxolane (6.49 g, 35.6 mmol) in hexanes (100 mL) was added 5% palladium on BaSO4 (1.14 g), and quinoline (freshly distilled from Zn dust, 0.631 ml, 5.34 mmol). The flask was then purged with H2 and stirred under an H2 atmosphere for 2 h. The reaction mixture was filtered through celite and washed sequentially with 1N HCl (2×) and brine. The organics were dried over MgSO4, filtered, and concentrated to give (R,Z)-4-(hex-3-enyl)-2,2-dimethyl-1,3-dioxolane which was used without further purification. This material contained approximately 7% of the trans olefin isomer which was carried through the synthetic route as a mixture (data not shown for minor isomer) eventually producing the corresponding exo-ethyl pyrazole acid derivative after separation by reverse phase HPLC (vide infra). 1H NMR (400 MHz, CDCl3): δ 5.40 (1H, m), 5.31 (1H, m), 4.06 (2H, m), 3.52 (1H, t, J=4.8 Hz), 2.09 (4H, m), 1.71 (1H, m), 1.54 (1H, m), 1.41 (3H, s), 1.35 (3H, s), 0.96 (3H, t, J=Hz).

1. distillationfreshly distilled from Zn dust, 0.631 ml, 5.34 mmol)
2. customThe flask was then purged with H2
3. filtrationThe reaction mixture was filtered through celite
4. washwashed sequentially with 1N HCl (2×) and brine
5. dry with materialThe organics were dried over MgSO4
6. filtrationfiltered
7. concentrationconcentrated