Lithium Hydroxide → 4-Isopropoxy-3-methylbenzoic acid

Temperatur

65 °C

To methyl 4-hydroxy-3-methyl-benzoate (1.0 g, 59.8 mmol) in dry DMF (62 mL) was added finely ground potassium carbonate (33.1 g, 239.3 mmol) followed by 2-iodopropane (20.3 g, 12.0 mL, 119.6 mmol). The reaction mixture was heated at 60° C. for 2 hours. The reaction mixture was cooled and diluted with ether (350 mL), and filtered over celite. The filtrate was washed with water (3×100 mL) and brine (100 mL) solution. The layers were separated and organics were dried over MgSO4. The solvent was evaporated and resulting residue was purified by silica gel using 0-30% EtOAc/hexanes mixtures as eluent to give methyl 4-isopropoxy-3-methylbenzoate as a colorless oil (11.2 g, 89%). ESI-MS m/z calc. 208.25. Found 209.2 (M+1)+; Retention time: 1.93 minutes (3 min run). Lithium hydroxide (4.4 g, 181.6 mmol) was added to a solution of methyl 4-isopropoxy-3-methylbenzoate (11.2 g, 53.8 mmol) in tetrahydrofuran (31 mL) and water (31 mL). The mixture was rapidly stirred and heated at 65° C. for 6 hours. The reaction mixture was cooled, diluted with water (75 mL) and extracted with ether (2×50 mL). The aqueous layer was acidified to pH 2 with 6N aq. HCl and extracted with ethyl acetate (4×75 mL). The combined organics were washed with water (75 mL) and brine solution (75 mL) and layers were separated. The organics were dried over MgSO4 and concentrated in vacuo to give 4-isopropoxy-3-methyl-benzoic acid (9.5 g, 82%) as colorless crystals. ESI-MS m/z calc. 194.2. Found 195.3 (M+1)+; Retention time: 1.53 minutes (3 min run). 1H NMR (400 MHz, DMSO) δ 7.78-7.71 (m, 2H), 7.02 (d, J=8.6 Hz, 1H), 4.70 (dt, J=12.1, 6.0 Hz, 1H), 2.15 (s, 3H), 1.30 (d, J=6.0 Hz, 6H).

1. customRetention time: 1.93 minutes (3 min run)
2. temperatureThe reaction mixture was cooled
3. extractionextracted with ether (2×50 mL)
4. extractionextracted with ethyl acetate (4×75 mL)
5. washThe combined organics were washed with water (75 mL) and brine solution (75 mL) and layers
6. customwere separated
7. dry with materialThe organics were dried over MgSO4
8. concentrationconcentrated in vacuo

ORD-Eintrag

ord-ee81feeaac7147cab0310dac9feefda8

Quelldatensatz

uspto-grants-2014_09

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US08828996B2