Isobutyric Acid → 2,2-Dimethyl-3-phenylpropanoic acid

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To a mixture of 1.23 g (41.0 mmol) of 80% sodium hydride and 50 mL of anhydrous tetrahydrofuran under a nitrogen atmosphere, was added 3.88 g (38.3 mmol) of diisopropylamine and then 3.3 g (37.5 mmol) of isobutyric acid. After heating at reflux for 5 minutes and cooling to 0° C., 15 mL (37.5 mmol) of 2.5M n-butyllithium in hexane was added. The mixture was warmed to 35° C. for 30 min, cooled to 0° C. and 6.40 g (37.5 mmol) of benzyl bromide added. The mixture was stirred for 30 minutes at 0° C., then warmed to 35° C. for one hour and recooled to 0° C. Water was added and the aqueous layer extracted with diethyl ether, acidified with 6N aqueous HCl and extracted with diethyl ether. The organic layer was dried and concentrated to provide 4.0 g of crude product. Chromatography on silica gel using 10% methanol/methylene chloride afforded 1.0 g of pure 2,2-dimethyl-3-phenylpropionic acid, m/e 185 (M+Li).

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