4-Bromo-1,1,2-trifluorobut-1-ene → 7,8,8-Trifluoro-7-octenoic acid

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Reaction Steps

A solution of 4-bromobutyric acid (8.35 g, 0.05 mole) in anhydrous THF (100 mL) is treated dropwise with methyl magnesium chloride (0.051 mole, 17 mL of 3M solution in THF) at -25° C. with stirring in 15 min. The solution is stirred for an additional 15 min at 0° C. and treated with dilithium tetrachlorocuprate (0.002 mole, 20 mL of 0.1M solution in THF) followed by 3,4,4-trifluoro-3-butenyl magnesium bromide (0.0565 mole, prepared separately from 3,4,4-trifluoro-3-butenyl bromide and magnesium turnings in THF). The mixture is stirred at 0° C. for 2 h and at room temperature for overnight. The solution is then poured in 400 mL of ether and 150 mL of 10% aqueous sulfuric acid. The ether layer is extracted with 10% NaOH (2×50 mL). The aqueous layer is washed with ether, acidified with conc. HCl, and extracted with ether (3×100 mL). The ether extract is dried, concentrated, and the residue distilled under vacuum to give 4.1 g of the desired product as a colorless liquid, a 42% yield. b.p. 125°-127° C./10 Torr.

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