Сообщение
pirazol » Сб фев 04, 2023 8:01 pm
A stock solution of 4-hydroxybenzoic acid (1) (200 mmol, 27.6 g) in H2SO4/H2O (9:1,445.5 mL/49.5 mL, 0.4 M) and a stock solution of isopropyl alcohol (6 eq., 1.2 mol, 71.5 g,91.3 mL) in H2SO4/H2O (9:1, 363 mL/40.7 mL) were heated at 35 °C and pumped using theAFR Corning module pump at a flow rate of 1.25 mL.min-1 for each solution through aT-mixer heated at 60 °C and a 100 mL coil PFA reactor also heated at 60 °C. The output ofthe reactor was collected into a stirred solution of H2O/toluene (1:1) at room temperature.The setup was eluted by a solution of H2SO4/H2O (9:1). The layers were separated and theaqueous phase was extracted with toluene. The combined organics phases were washedwith brine, dried with MgSO4, and concentrated under vacuum. Flash chromatographyafforded the desired product 2 as a white solid (84%, 168 mmol, 37.3 g).1H NMR (300 MHz, CDCl3) δ 7.87 (s, 2H), 3.17 (hept, J = 6.9 Hz, 2H), 1.31 (d, J = 6.9Hz, 12H). 13C NMR (75 MHz, Chloroform-d) δ 172.64, 155.15, 133.73, 126.50, 121.47, 27.22,22.60. Melting point: 139-142°C. GC retention time: 19.02 min.
To the solution of 4-hydroxy-3,5-diisopropyl benzoic acid lOOg (0.45 M) (example 1) in ethylene glycol (150 ml) was added sodium hydroxide pallets 41.5g (1.03M) and heated to 140- 145 °C under inert atmosphere. After 7 hrs of continued heating at 140-145°C, the react4on mass was cooled to room temperature and diluted with 5 times water. The pH of the mass was then adjusted to 1-2 using concentrated Hydrochloric acid, reaction mixtiire was stirred for one hour and extracted three times with 200 ml toluene, combined toluene layers were washed twice with 5 % aq. sodium bicarbonate solution (50 ml) and finally with water (200 ml), solvent was removed under reduced pressure and a dark brown colored residue which remained was distilled under high vacuum condition (0.2 mm/Hg) to yield 75g ( 93.5%) of 2,6- diisopropyl phenol collected as a colourless to pale yellow oily liquid, HPLC Purity 99.93 %.