To a solution of diethyl 2-(1,1-dimethylpropyl)propanedioate (2.4 g, 9.9001 mmol) in DMSO (50 mL) and water (10 mL) was added lithium hydroxide hydrate (2.1 g, 50.043 mmol) and the mixture was stirred at 120 °C for 22 hours. The mixture was acidified to pH 2-3 with 1N hydrochloric acid and extracted with ethyl acetate (2 x 40 mL). The combined organic layers were washed with brine (3 x 30 mL) and water (30 mL), dried over sodium sulfate, filtered, and concentrated under reduced pressure to give 3,3-dimethylpentanoic acid (1.23 g, 91%) as a yellow oil.
