638-07-3

141-97-9

638-07-3

GENERAL PROCEDURE: To an anhydrous THF (2 mL) solution of diisopropylamine (340 μL, 2.4 eq.) in a flame-dried round-bottomed flask under an argon atmosphere at 0 °C, n-butyllithium (1.4 mL, 1.6 M hexane solution, 2.2 eq.) was slowly added and the reaction mixture was stirred at this temperature for 15 min. Maintaining the same temperature, a solution of THF (2 mL) in ethyl acetoacetate (1 mmol) was slowly added dropwise. The reaction mixture was cooled to -78 °C after continued stirring at 0 °C for 1 h. Methyl chlorosulfate (110 μL, 1.2 eq.) was subsequently added. After stirring at -78 °C for 30 min, the reaction was quenched by the addition of saturated aqueous ammonium chloride solution (5 mL). The mixture was extracted with dichloromethane (3 x 5 mL) and the organic phases were combined and dried over anhydrous magnesium sulfate. Evaporation of the solvent gave the target product ethyl 4-chloroacetoacetate.