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温度

0 °C

A 1 L 3-neck round bottom flask equipped with a mechanical stirrer and addition funnel was charged with 252B (14.7 g, 39 mmol) and acetonitrile (200 mL) and acetic acid (100 mL). The solution was cooled to 0° C. and Na(OAc)3BH (33.3 g, 157 mmol) was added in three portions over 2 hours. The reaction was stirred for two hours at this temperature after the final addition. The mixture was then cooled to −10° C. and slowly quenched by addition of 1 N NaOH (100 mL), 4 N NaOH (100 mL), 6 N NaOH (100 mL) followed by 50% NaOH (50 mL). The reaction was warmed to room temperature and the layers were separated. The aqueous layer was extracted with CH2Cl22 (2×250 mL) and the combined organic layers were dried (Na2SO4), filtered and concentrated in vacuo. Purification by flash chromatography (10% to 30% EtOAc/hexane gradient) on silica gel afforded 6.0 g (yield: 41%) of Compound 252C.

1. customA 1 L 3-neck round bottom flask equipped with a mechanical stirrer and addition funnel
2. additionaddition
3. temperatureThe mixture was then cooled to −10° C.
4. customslowly quenched by addition of 1 N NaOH (100 mL), 4 N NaOH (100 mL), 6 N NaOH (100 mL)
5. temperatureThe reaction was warmed to room temperature
6. customthe layers were separated
7. extractionThe aqueous layer was extracted with CH2Cl22 (2×250 mL)
8. dry with materialthe combined organic layers were dried (Na2SO4)
9. filtrationfiltered
10. concentrationconcentrated in vacuo
11. customPurification by flash chromatography (10% to 30% EtOAc/hexane gradient) on silica gel