Reaktion #1124901

Reaktionsgleichung

water

3-bromo-4,5-dimethyl-4,5-dihydro-6H-cyclopenta[b]thiophen-6-one

NaBH4

→

4,5-Dimethyl-4H-cyclopenta[b]thiophene

Lösungsmittel

THF methanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGThis mixture was stirred overnight at ambient temperature
2. 2
   SonstigeThe organic layer was separated
3. 3
   Extraktionthe aqueous layer was extracted with 2×300 ml of methyl-tert-butyl ether
4. 4
   ExtraktionThe combined extract
5. 5
   Trocknenwas dried over K2CO3
6. 6
   Sonstigeevaporated to dryness
7. 7
   workup.ADDITIONTo a hot solution of the residue in 1500 cm3 of toluene, 0.5 g of para-toluenesulfonic acid was added
8. 8
   TemperaturThis mixture was refluxed for 15 min
9. 9
   Temperaturcooled to room temperature
10. 10
    WaschenThe column was additionally washed with hexanes
11. 11
    Sonstigeto isolate the product
12. 12
    SonstigeThe obtained solution was evaporated to dryness
13. 13
    workup.DISTILLATIONFractional distillation
14. 14
    Sonstigegave a colorless oil, bp 101-104° C./2 mm Hg

Vorschrift

To a solution of 132.4 g (0.54 mol) of 3-bromo-4,5-dimethyl-4,5-dihydro-6H-cyclopenta[b]thiophen-6-one in 750 ml of THF-methanol (2:1, vol.), 28.6 g (0.75 mol) of NaBH4 was added in small portions while vigorously stirring over 1 h at 5° C. This mixture was stirred overnight at ambient temperature and then added to ca. 1000 cm3 of cold water. The organic layer was separated; the aqueous layer was extracted with 2×300 ml of methyl-tert-butyl ether. The combined extract was dried over K2CO3 and evaporated to dryness. To a hot solution of the residue in 1500 cm3 of toluene, 0.5 g of para-toluenesulfonic acid was added. This mixture was refluxed for 15 min, cooled to room temperature, and passed through a short Silica Gel 60 column (40-63 μm, d 65 mm, 1 150 mm). The column was additionally washed with hexanes to isolate the product. The obtained solution was evaporated to dryness. Fractional distillation gave a colorless oil, bp 101-104° C./2 mm Hg. Yield 92.8 g (75%).

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