反应详情

Sodium borohydride (log; 0.27 mol) was added slowly to a cold, stirring suspension of 53 g (0.25 mol) of 4,5-methylenedioxy-2-nitroacetophenone in 400 mL methanol. The temperature was kept below 10° C. by slow addition of the NaBH4 and external cooling with an ice bath. Stirring was continued at ambient temperature for another two hours, at which time TLC (CH2Cl2) indicated complete conversion of the ketone. The mixture was poured into one liter of ice-water and the resulting suspension was neutralized with ammonium chloride and then extracted three times with 400 mL CH2Cl2 or EtOAc (the product can be collected by filtration and washed at this point, but it is somewhat soluble in water and this results in a yield of only ˜60%). The combined organic extracts were washed with brine, then dried with MgSO4 and evaporated. The crude product was purified from the main byproduct by dissolving it in a minimum volume of CH2Cl2 or THF(˜175 ml) and then precipitating it by slowly adding hexane (1000 ml) while stirring (yield 51 g; 80% overall). It can also be recrystallized (e.g., toluene-hexane), but this reduces the yield.

1. temperatureexternal cooling with an ice bath
2. stirringStirring
3. extractionextracted three times with 400 mL CH2Cl2 or EtOAc (the product
4. filtrationcan be collected by filtration
5. washwashed at this point, but it
6. customthis results in a yield of only ˜60%)
7. washThe combined organic extracts were washed with brine
8. dry with materialdried with MgSO4
9. customevaporated
10. customThe crude product was purified from the main byproduct
11. dissolutionby dissolving it in a minimum volume of CH2Cl2 or THF(˜175 ml)
12. customprecipitating it by slowly adding hexane (1000 ml)
13. stirringwhile stirring (yield 51 g; 80% overall)
14. customIt can also be recrystallized (e.g., toluene-hexane)