Water → 4,5-dimethyl-4H-cyclopenta[b]thiophene

Temperature

5 °C

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, l 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%).

1. stirringThis mixture was stirred overnight at ambient temperature
2. customThe organic layer was separated
3. extractionthe aqueous layer was extracted with 2×300 ml of methyl-tert-butyl ether
4. extractionThe combined extract
5. dry with materialwas dried over K2CO3
6. customevaporated to dryness
7. additionTo a hot solution of the residue in 1500 cm3 of toluene, 0.5 g of para-toluenesulfonic acid was added
8. temperatureThis mixture was refluxed for 15 min
9. temperaturecooled to room temperature
10. washThe column was additionally washed with hexanes
11. customto isolate the product
12. customThe obtained solution was evaporated to dryness
13. distillationFractional distillation
14. customgave a colorless oil, bp 101-104° C./2 mm Hg

ORD record

ord-e0e05ff1df6f4d8780abaf4292e6d2e2

Source dataset

uspto-grants-2012_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08173828B2