反应详情

A solution of 2-[4-(3,4-dihydro-2H-1-benzopyran-6-yl)-2,5-dimethylthiophen-3-yl]-2-oxoacetic acid (42a) (1.09 g, 3.43 mmol) in methanol (10 mL) was cooled to 0° C. Trimethylsilyldiazomethane 2N in diethyl ether (6.89 mL, 13.7 mmol) was added dropwise and the reaction mixture was stirred at room temperature for 3 hours. The precipitate was filtered off and washed with cooled methanol (5 mL). The filtrate was concentrated in vacuo and the residue was dissolved in a minimum of methanol. The solution was sonicated for a few seconds and the precipitate was filtered and washed with cooled methanol. The precipitates were combined to provide the desired ester (42b) (820 mg, 2.48 mmol, 72% over two steps) as a beige solid, which was used without further purification.

1. filtrationThe precipitate was filtered off
2. washwashed with cooled methanol (5 mL)
3. concentrationThe filtrate was concentrated in vacuo
4. dissolutionthe residue was dissolved in a minimum of methanol
5. customThe solution was sonicated for a few seconds
6. filtrationthe precipitate was filtered
7. washwashed with cooled methanol