Реакция #1173114

Уравнение реакции

AcOH

qinghaosu

NaBH4

→

( II )

Выход 79.2%

Dihydroqinghaosu

Выход 79.2%

Растворители

MeOH

Условия реакции

Обработка

1. 1
   Другоеat 0°-5° C
2. 2
   Другоеin the 0°-5° C. range
3. 3
   Концентрированиеconcentrated
4. 4
   workup.DISTILLATIONby distilling off 8.5 l of solvent (45° C./400 mm)
5. 5
   workup.ADDITIONdiluted with 7.5 l cold H2O--MeOH (2:1, 0°-5° C.)
6. 6
   workup.WAITThe filtrate was stored for 14 h at 4° C
7. 7
   ДругоеThe small amount of precipitate formed
8. 8
   Другоеwas collected
9. 9
   Промывкаwashed with 2×30 ml H2O--MeOH (2:1, 0°-5° C.)
10. 10
    workup.DISSOLUTIONdissolved in 7 l CH2Cl2
11. 11
    ДругоеAfter drying
12. 12
    Другое(120 g MgSO4) and evaporation of the solvent

Методика

To a stirred solution of 240 g (0.85 mol) of qinghaosu (I) in 12 l MeOH was added 240 g (6.34 mol) NaBH4 over a period of 1.75 h, keeping the reaction mixture at 0°-5° C. After an additional stirring for 1.25 h under the same conditions, the mixture was neutralized with 375 ml AcOH maintaining the temperature in the 0°-5° C. range, concentrated by distilling off 8.5 l of solvent (45° C./400 mm), and diluted with 7.5 l cold H2O--MeOH (2:1, 0°-5° C.). The filtrate was stored for 14 h at 4° C. The small amount of precipitate formed was collected and washed with 2×30 ml H2O--MeOH (2:1, 0°-5° C.). The wet crops were pooled and dissolved in 7 l CH2Cl2. After drying (120 g MgSO4) and evaporation of the solvent, 191.4 g (79%) of (II) was obtained: mp 149°-153° C.

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