Allyl bromide → Cyclopropanecarboxylic acid, 1-(2-propenyl)-, 1,1-dimethylethyl ester

Temperatur

-75 °C

15.9 ml (1.15 equiv.) diisopropylamine were dissolved in 65 ml tetrahydrofuran and cooled to ca −10° C. 65 ml (1.08 equiv.) 1.6 M butyllithium solution in hexane were added over 25 min, maintaining the temperature between −10° C. and 0° C. After 50 nm in at ca. −5° C., the reaction mixture was cooled to −75° C. A solution of 15 g (96.7 mmol, 1 equiv., 92% w/w purity) cyclopropanecarboxylic acid tert-butyl ester in 20 ml tetrahydrofuran was added over 15 min keeping the temperature between −75° C. and −70° C. The reaction mixture was stirred 5 h at −75° C. (milky reaction mixture obtained after 2.5 h). A solution of 12.87 g (1.10 equiv.) allyl bromide was added over 20 min keeping the temperature between −75° C. and −60° C. The reaction mixture was stirred at −78° C. for 1 h, warmed to room temperature and stirred overnight. The reaction mixture was cooled to 0° C. 100 ml sat. aq. ammonium chloride solution were added followed by 30 ml water providing a clear biphasic mixture. The mixture was extracted 3 times with 50 ml tert-butyl methyl ether. The organic phases were combined, dried over sodium sulfate, filtered and concentrated under reduced pressure (40° C./20 mbar) to afford 16.44 g of crude product. The crude product was distilled (2 mbar; ca 40° C. distillation head temperature) to provide the title compound in ca 65% yield.

1. temperaturecooled to ca −10° C
2. temperaturemaintaining the temperature between −10° C. and 0° C
3. customthe temperature between −75° C. and −70° C
4. custom(milky reaction mixture obtained after 2.5 h)
5. customthe temperature between −75° C. and −60° C
6. stirringThe reaction mixture was stirred at −78° C. for 1 h
7. temperaturewarmed to room temperature
8. stirringstirred overnight
9. temperatureThe reaction mixture was cooled to 0° C
10. extractionThe mixture was extracted 3 times with 50 ml tert-butyl methyl ether
11. dry with materialdried over sodium sulfate
12. filtrationfiltered
13. concentrationconcentrated under reduced pressure (40° C./20 mbar)
14. customto afford 16.44 g of crude product
15. distillationThe crude product was distilled
16. distillation(2 mbar; ca 40° C. distillation head temperature)

ORD-Eintrag

ord-b7312a974bb244fe9fd3b87cdfbac3bd

Quelldatensatz

uspto-grants-2011_11

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US08063042B2