Lithium Bromide → 2-Isobutyl-succinic acid-4-t-butyl ester

Participants

Reaction Steps

Synthesis of Compound 1 Lithium aluminum hydride (69.4 mL of a 1 M solution in ether, 69.4 mmol) was added dropwise to a stirring solution of cis-cyclobutane-1,2-dicarboxylic acid (5 g, 34.7 mmol) in THF (60 mL) at 0° C. under argon. The mixture was allowed to warm to room temperature and stirred for 16 hours. The mixture was cooled to 0° C. and quenched by careful addition of water (2.7 mL), sodium hydroxide solution (2.7 mL of a 15% w/v solution), and water (8.1 mL). The mixture was stirred for 15 minutes, and the precipitate was removed by filtration. The solvent was evaporated under reduced pressure to give the alcohol 1 as a colorless oil (4.0 g, 98%); δH (400 MHz; CDCl3): 3.85 (2H, m), 3.6 (2H, m), 3.2 (2H, s), 2.7 (2H, m), 2 (2H, m); 1.55 (2H, m); δC (400 MHz; CDCl3): 63.15, 37.83, 20.40. Synthesis of Compound 2 Mesyl chloride (6.2 mL, 79.1 mmol) was added dropwise to a stirring solution of 1 (4.0 g, 34.4 mmol) in dichloromethane (150 mL) at −40° C. under argon. Triethylamine (12.0 mL, 86.0 mmol) was then added dropwise, and the mixture was allowed to warm slowly to room temperature. After stirring for 16 hours, the mixture was quenched by addition of dilute hydrochloric acid (50 mL). The organic layer was separated, and the aqueous layer was further extracted with dichloromethane (2×50 mL). The combined organic fractions were washed with brine, dried (MgSO4), and the solvent was evaporated under reduced pressure. The residue was chromatographed (SiO2, heptane/ethyl acetate, 6:4) to give the mesylate 2 (6.1 g, 73%) as a white solid; Rf(heptane/ethyl acetate, 1:1) 0.18. δH (400 MHz; CDCl3): 4.3 (4H, m), 3.05 (6H, s), 2.9 (2H, m), 2.2 (2H, m), 1.8 (2H, m); δc(400 MHz; CDCl3): 69.51, 37.45, 35.28, 21.09. Synthesis of Compound 3 Anhydrous lithium bromide (10.6 g, 121.8 mmol) was added to a stirring mixture of 2 (5.95 g, 24.4 mmol) in acetone (50 mL) under argon, and the mixture was refluxed for 2 hours. After cooling, the acetone was evaporated under reduced pressure, and the residue was taken up in ether (50 mL), washed with water (50 mL), brine, dried (MgSO4), and the solvent was evaporated under reduced pressure. The residue was chromatographed (SiO2, heptane/ethyl acetate, 95:5) to give the dibromide 3 (5.36 g, 86%) as an orange liquid; Rf (heptane-ethyl acetate,

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