Methyl acetoacetate → 6-(2-Cyclohex-1-enyl-ethyl)-6-cyclopentyl-dihydro-pyran-2,4-dione

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Reaction Steps

Methyl acetoacetate (0.66 g, 5.7 mmol) was added to a cooled 0° C. suspension of NaH (0.23 g, 5.7 mmol, 60% dispersion in mineral oil) in THF (10 ml). After 30 min n-BuLi (2.3 mL, 5.7 mmol, 2.5M in hexanes) was added. The resulting dianion was stirred for an additional 30 min and then treated with a solution 3-Cyclohex-1-enyl-1-cyclopentyl-propan-1-one (0.39 g, 1.9 mmol, Step 4 below (in THF (3 ml). After stirring for 4 h at 0° C., the reaction mixture was quenched with 1N HCl and extracted with EtOAc. The organic layers were washed with brine, dried over Na2SO4 and concentrated to an orange oil that was used without further purification. The oil was dissolved in methanol (8 mL), treated with potassium carbonate (0.79 g, 5.7 mmol), and refluxed under N2 for 90 min. The reaction mixture was partitioned between 1N HCl and EtOAc. The organic layers were washed with brine, dried over Na2SO4 and concentrated to an orange oil that was purified by silica gel chromatography (0% to 20% EtOAc in hexanes). to give the title compound as a white solid. (0.22 g, 40% yield). 1H NMR (CDCl3): δ 1.42-1.98 (br m, 20H), 2.22 (m, 1H), 2.71 (s, 2H), 3.40 (s, 2H), 5.40 (s, 1H). Anal. Calcd. For C18H26O3.0.2H2O: C, 75.53; H, 9.05. Found: C, 73.74; H, 9.01.

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