反应详情

A solution of 2-cyclohexen-1-one (20 g, 0.208 mmol) in tetrahydrofuran (250 ml) was added to a preformed lithium diisopropylamide solution (prepared from diisopropylamine (31 ml) and n-butyllithium (140 ml, 1.6M solution) at −70° C.) over 20 minutes and stirred for a further 20 minutes. Ethyl bromoacetate (25 ml, 0.228 mmol) was added dropwise and the reaction stirred for 1 hour warming to room temperature. The reaction was quenched with 6N HCl (200 ml) and the product extracted into ether (3×300 ml). Combined organic phase washed with saturated sodium chloride, dried over magnesium sulfate and evaporated to dryness. The crude oil was purified by silica chromatography eluting with hexane-ethyl acetate mixtures (10-20%), to give ethyl (2-oxo-cyclohex-3-enyl)acetate as a colourless oil, 11.8 g. 1H NMR δ (ppm) (CDCl3): 6.98-6.94 (1H, m), 6.03-6.00 (1H, m), 4.19-4.11 (2H, m), 2.92-2.82 (2H, m), 2.49-2.41 (2H, m), 2.30-2.23 (1H, m), 2.16-2.11 (1H, m), 1.87-1.77 (1H, m) and 1.28-1.24 (3H, m).

1. stirringthe reaction stirred for 1 hour
2. customThe reaction was quenched with 6N HCl (200 ml)
3. extractionthe product extracted into ether (3×300 ml)
4. washCombined organic phase washed with saturated sodium chloride
5. dry with materialdried over magnesium sulfate
6. customevaporated to dryness
7. customThe crude oil was purified by silica chromatography
8. washeluting with hexane-ethyl acetate mixtures (10-20%)