20583-33-9

1423-60-5

18107-18-1

20583-33-9

Example 18, Step A: Trimethylsilylated diazomethane (50 mL, 2 M hexane solution, 300 mmol) was added slowly and dropwise to a solution of but-3-yn-2-one (20.4 g, 300 mmol) in tetrahydrofuran (THF, 250 mL), and the temperature was maintained at 20-30 °C during the reaction using an ice bath (delayed exothermic phenomena were observed). The reaction mixture was stirred continuously for 3 h at room temperature. Upon completion of the reaction, it was quenched by the addition of water (500 mL) and subsequently extracted with ethyl acetate (EtOAc). The organic layers were combined, dried over anhydrous sodium sulfate (Na2SO4), filtered and the filtrate was concentrated under reduced pressure to give the target product 18b (31 g, 94% yield).