1,3-Dibromo-5,5-dimethylhydantoin → 2-(1-Bromoethyl)benzo[b]thiophene

Temperature

20 °C

A solution of 9.78 g (60 mmol) of 2-ethylbenzo[b]thiophene in 10 ml of heptane is added, over 10 minutes, to a mixture of 9.43 g (33 mmol) of 1,3-dibromo-5,5-dimethylhydantoin and 0.49 g (3 mmol) of azobisisobutyronitrile in 117.5 ml of heptane preheated to 60° C. The mixture is maintained for 1 additional hour at this temperature. After cooling to 20° C., stirring is continued for 1 hour and then the 5,5-dimethylhydantoin which has precipitated is filtered off and washed with 10 ml of heptane. The filtrate is washed with an aqueous sodium thiosulphate solution (3 g/100 ml) and then with 3 times 100 ml of water. After drying over sodium sulphate, the heptane phase is concentrated to approximately 40 ml and then cooled to -10° C. for one hour and a half. The precipitate formed is filtered off and dried under partial vacuum at 20° C. to provide 9.05 g of the desired compound in the form of a beige powder, which represents a yield of 57% (M.p.: 53° C., purity by liquid phase chromatography: 92%). A second, less pure sample is obtained by concentrating the mother liquors (16%).

1. custompreheated to 60° C
2. temperatureThe mixture is maintained for 1 additional hour at this temperature
3. customthe 5,5-dimethylhydantoin which has precipitated
4. filtrationis filtered off
5. washwashed with 10 ml of heptane
6. washThe filtrate is washed with an aqueous sodium thiosulphate solution (3 g/100 ml)
7. dry with materialAfter drying over sodium sulphate
8. concentrationthe heptane phase is concentrated to approximately 40 ml
9. temperaturecooled to -10° C. for one hour
10. customThe precipitate formed
11. filtrationis filtered off
12. customdried under partial vacuum at 20° C.

ORD record

ord-f26f23b434bd4e9ebe55caafa7173cce

Source dataset

uspto-grants-1995_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05420300