反応 #1173115

反応方程式

AcOH

qinghaosu

NaBH4

→

( II )

収率 88.0%

Dihydroqinghaosu

収率 88.0%

溶媒

water

MeOH

反応条件

後処理

1. 1
   その他at 0°-5° C
2. 2
   その他in the range of 0°-5° C.
3. 3
   workup.STIRRINGAfter stirring for 1 h at 0°-1° C.
4. 4
   その他the white precipitate formed
5. 5
   その他was collected
6. 6
   洗浄washed with 700 ml water-MeOH (2:1, 0°-5° C.) The filtrate
7. 7
   workup.STIRRINGwas stirred for 14 h at 0° C
8. 8
   その他The small amount of material precipitated
9. 9
   その他was collected
10. 10
    洗浄washed with H2O--MeOH (2:1, 2×30 ml)
11. 11
    workup.DISSOLUTIONdissolved in 7 l CH2Cl2
12. 12
    その他After drying on magnesium sulphate (120 g) and evaporation of the solvent

実験手順

To a stirred solution of qinghaosu (I) (240 g, 0.85 mol) in 12 l MeOH was added NaBH4 (240 g, 6.34 mol) over a period of 2 h keeping the reaction mixture at 0°-5° C. After an additional stirring for 1.30 h under the same conditions, the mixture was neutralized with 375 ml AcOH maintaining the temperature in the range of 0°-5° C. and subsequently diluted with 24 l water. After stirring for 1 h at 0°-1° C., the white precipitate formed was collected and washed with 700 ml water-MeOH (2:1, 0°-5° C.) The filtrate was stirred for 14 h at 0° C. The small amount of material precipitated was collected and washed with H2O--MeOH (2:1, 2×30 ml). The wet crops were combined and dissolved in 7 l CH2Cl2. After drying on magnesium sulphate (120 g) and evaporation of the solvent, 212 g (88%) of (II) was obtained: mp 149°-153° C.

出典