Ethyl 2-(diethoxyphosphoryl)butanoate → HCID 68850618, compound

Under an argon atmosphere, triethyl 2-phosphonobutyrate (3.77 g, 14.9 mmol) was dissolved in dehydrated tetrahydrofuran (40 mL) and potassium tert-butoxide (1.68 g, 15.0 mmol) was added under stirring and cooling with ice. After completion of the addition, the mixture was stirred for 1 hour. Following this, benzyl 2-methylthio-2-(5-formyl-2-methoxyphenyl)acetate (4.49 g, 13.6 mmol) dissolved in dehydrated tetrahydrofuran (30 mL) was added and the mixture was stirred for 6 hours at room temperature. The reaction mixture was concentrated and ice water was added, which was made acidic with 1 mol/L hydrochloric acid. The reaction mixture was extracted with ethyl acetate. The extracte was washed with water and brine, dried over anhydrous sodium sulfate, and then concentrated. The residue was purified by silica gel column chromatography (eluent n-hexane:ethyl acetate=9:1 v/v) to afford 4.55 g (78%) of the title compound as a colorless oil.