Acetyl chloride → methyl (1R,3S)-3-acetyl-2,2-dimethylcyclobutanecarboxylate

Acetyl chloride (1.02 ml, 14.32 mmol) was added dropwise to MeOH (10 mL) at 0° C. and the resulting mixture was stirred at 0° C. for 30 mins. (1R,3S)-3-acetyl-2,2-dimethylcyclobutanecarboxylic acid from Step 1 (696 mg, 4.09 mmol) was added as a solution in MeOH (2 mL) and the reaction mixture was stirred overnight while warming up to room temperature. The volatiles were then removed under reduced pressure and the residue was purified by flash chromatography on silica gel (gradient elution, 2% to 20% EtOAc in Hexanes) to give methyl (1R,3S)-3-acetyl-2,2-dimethylcyclobutanecarboxylate as a colorless oil. MS ESI calc'd. for C10H17O3 [M+H]+ 185. found 185. 1H NMR (500 MHz, CDCl3) δ 3.66 (s, 3H), 2.88 (dd, J=10.5, 7.6 Hz, 1H), 2.78 (dd, J=10.8, 8.1 Hz, 1H), 2.64 (app q, J=10.8 Hz, 1H), 2.06 (s, 3H), 1.92-1.87 (m, 1H), 1.43 (s, 3H), 0.89 (s, 3H).