PMGB

A 1.6 M solution of n-butyllithium in hexane (9.36 mL) was added to a stirred solution of diisopropylamine (2.22 mL) in THF (15 mL) at -5 to 0 ^oC. After being stirred at -5 to 0 ^oC for 30 min, the reaction mixture was cooled to -78 ^oC and ethyl isobutyrate (1.9 mL) was added. Stirring was continued at -78 ^oC for 45 min. A solution of 1-bromo-2-chloroethane (1.19 mL) in THF (1 mL) was then added dropwise to the mixture. The whole was further stirred at -78 ^oC for 1 h and at room temperature for 2 h, then poured into an excess of aqueous NH₄Cl solution and extracted with ethyl acetate, the extract was washed with brine, dried over MgSO₄, and evaporated in vacuum to give a residue, which was distilled to give ethyl 4-chloro-2,2-dimethylbutanoate isolated as a colorless oil, 2.1 g. NMR complies.

Ref: Chem. Pharm. Bull. 1997, 45, 1447-1457.