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0 °C

Preparation of 4-Isobutyl-dihydro-furan-2-one (4): A solution of 2-isobutyl-succinic acid-4-t-butyl ester (8.0 g, 34.7 mmol) in 100 mL of THF is cooled to 0° C. under Ar and borane dimethyl sulphide complex (2.6 g, 34.7 mmol) is added. The reaction mixture is stirred at 0° C. for 10 minutes, and at room temperature overnight. The solution is cooled to 0° C. and 100 mL of MeOH is added. The solvents are evaporated, and the remaining oil is dried under hi-vacuum for 2 hrs. The oil remaining is taken up in 100 mL of THF, and a catalytic amount of p-toluene sulfonic acid is added. The solution is warmed to reflux overnight. After being cooled to room temperature, the solvent is evaporated, and the oil is taken up in Et2O (100 mL). The Et2O solution is extracted with 2.0N Na2CO3 (2×50 mL) followed by 100 mL of brine and dried over MgSO4. Evaporation of Et2O followed by medium pressure chromatography (MPLC) of the remaining oil in 20% EtOAc/Hexanes gives 4.4 g (89% yield) of 4-isopropyl-dihydro-furan-2-one as an oil. NMR (H1, 400 MHz, CDCl3) δ0.9 (6H, m); δ1.3 (2H, dd); δ1.5 (1H, m); δ2.1 (1H, m); δ2.6 (2H, m); δ3.6 (1H, m); δ4.4 (1H, m).

1. additionis added
2. customat room temperature
3. customovernight
4. temperatureThe solution is cooled to 0° C.
5. customThe solvents are evaporated
6. customthe remaining oil is dried under hi-vacuum for 2 hrs
7. additiona catalytic amount of p-toluene sulfonic acid is added
8. temperatureThe solution is warmed
9. temperatureto reflux overnight
10. temperatureAfter being cooled to room temperature
11. customthe solvent is evaporated
12. extractionThe Et2O solution is extracted with 2.0N Na2CO3 (2×50 mL)
13. dry with materialdried over MgSO4
14. customEvaporation of Et2O