反应详情

A round-bottom flask was charged with ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (2.04 g, 12.1 mmol, Preparation #CC.1), MeOH (30 mL), and cerium(III) chloride heptahydrate (5.65 g, 15.2 mmol) followed by portion-wise addition of sodium borohydride (0.574 g, 15.2 mmol). The suspension was stirred at room temperature over about 16 h. Saturated aqueous NH4Cl solution (50 mL) was added. The mixture was stirred for about 10 min and Et2O (60 mL) was added. The layers were separated and the aqueous layer was extracted with Et2O (3×30 mL). The combined organic layers were washed with saturated aqueous NaHCO3, dried over anhydrous MgSO4, filtered, and concentrated to dryness under reduced pressure. The residue was purified via silica gel chromatography eluting with 20-60% EtOAc/pentane to yield cis-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.96 g, 46%): 1H NMR (400 MHz, CDCl3) δ 5.77-5.71 (m, 1H), 4.63 (m, 1H), 4.28-4.11 (m, 2H), 3.27-3.20 (m, 1H), 2.59 (bs, 1H), 2.41-2.30 (m, 1H), 2.00 (d, J=14.2 Hz, 1H), 1.79 (d, =1.2 Hz, 3H), 1.30 (t, J=7.1 Hz, 3H) and trans-ethyl 4-hydroxy-2-methylcyclopent-2-enecarboxylate (0.69 g, 33%): 1H NMR (400 MHz, CDCl3) δ 5.63 (dd, J=1.8, 3.4 Hz, 1H), 4.98 (m, 1H), 4.20-4.11 (m, 2H), 3.60-3.53 (m, 1H), 2.57 (ddd, J=4.4, 7.1, 13.9 Hz, 1H), 1.98 (ddd, J=3.5, 8.4, 13.9 Hz, 1H), 1.80 (d, J=1.4, 3H), 1.46 (bs, 1H), 1.27 (t, J=7.1 Hz, 3H).

1. stirringThe mixture was stirred for about 10 min
2. customThe layers were separated
3. extractionthe aqueous layer was extracted with Et2O (3×30 mL)
4. washThe combined organic layers were washed with saturated aqueous NaHCO3
5. dry with materialdried over anhydrous MgSO4
6. filtrationfiltered
7. concentrationconcentrated to dryness under reduced pressure
8. customThe residue was purified via silica gel chromatography
9. washeluting with 20-60% EtOAc/pentane