Methyl acetoacetate → 6-Cyclopentyl-6-[2-(2,4-dimethoxyphenyl)ethyl]tetrahydropyran-2,4-dione

Participants

Reaction Conditions

Reaction Steps

Methylacetoacetate (1.63 mL, 15.1 mmol) was dissolved in dry THF (42 mL) and cooled to 0° C. NaH (60% in mineral oil, 0.604 g, 15.1 mmol) were carefully added and the reaction mixture was stirred for 20 min. A solution of BuLi in hexanes (1.6 M, 9.44 mL, 15.1 mmol) was added dropwise and the resulting mixture was stirred an additional 20 min. A solution of 3-(2,4-dimethoxyphenyl)-1-cyclopentylpropan-1-one (2.33 g, 7.55 mmol) from Step 4 above in THF (37 mL) was added dropwise. After stirring 1 h, the reaction mixture was quenched with saturated aq NH4Cl (100 mL) and extracted with Et2O (600 mL). The organic phase was dried over MgSO4 and evaporated. The residue was then stirred overnight in a mixture of 0.1 M NaOH (370 mL) and THF (37 mL). After the addition of solution of 10% aqueous KHSO4 (50 mL), the resulting mixture was stirred 30 min and then extracted with Et2O (600 mL). The organic phase was washed with brine, dried over MgSO4 and evaporated. The residue was purified by flash column chromatography (50% EtOAc in hexanes) to give the product (1.54 g, 52%) as a white foam. 1H NMR (CDCl3) δ 1.43 (m, 2 H), 1.78 (m, 8 H), 2.33 (m, 1H), 2.58 (m, 2H), 2.78 (s, 2H), 3.43 (s, 2H), 3.78 (s, 6H), 6.37 (s, 1H), 6.47 (s, 1H), 6.93 (d, J=7.93 Hz, 1H). MS (APCI) calcd for C20H26O5: 346.2; found (M+1): 347.0.

Provenance & Evidence