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[Diman1133]

Доброго времени суток! Пожалуйста, помогите найти DOI статьи, где была бы указана методика получения метилового эфира 2,4-дигидроксибензойной кислоты (Methyl 2,4-dihydroxybenzoate)( CAS 2150-47-2) из самой кислоты и метанола. Спасибо!

[mishka]

With sulfuric acid for 20h; Reflux;
DOI 10.1016/j.tet.2009.03.089

With sulfuric acid In water for 120h; Reflux; Inert atmosphere;
DOI 10.1039/c3ob41951g

With sulfuric acid at 70℃; for 24h;
DOI 10.14233/ajchem.2014.15485

With sulfuric acid for 24h; Reflux;
DOI 10.1016/j.ejmech.2016.06.044
Experimental Procedure
90%
Sakthivel, Palaniappan; Ilangovan, Andivelu; Kaushik, Mahabir Prasad
[European Journal of Medicinal Chemistry, 2016, vol. 122, p. 302 - 318]
Experimental Procedure
4.1.2. Methyl 2,4-dihydroxybenzoate (2) [60]
To a stirred solution of 2,4-dihydroxybenzoicacid (1, 10.00 g,64.93 mmol) in methanol (100 mL) was added catalytic amount ofCon.H2SO4 (0.35 mL, 6.49 mmol) and stirred at reflux for 24 h. Aftercompletion of the reaction methanolwas evaporated and quenchedwith ice water and basified into pH 8 using aq.Na2CO3 solution.Then precipitated solid was filtered off, washed with ice water andthen dried. The title compound 2 (9.80 g, 90%) was obtained as palebrown solid. This is pure enough for further step. M.p. 118-120° C.

With sulfuric acid for 96h; Reflux; Inert atmosphere;
DOI 10.1080/00397911.2012.681827

With sulfuric acid for 20h; Reflux;
DOI 10.1039/c9cc07768e

With sulfuric acid Fischer–Speier Esterification; Reflux;
DOI 10.1039/d0md00366b

With sulfuric acid at 100℃; for 24h; Inert atmosphere;
DOI 10.1016/j.ejmech.2016.10.038
Experimental Procedure
4.1.1 Methyl 2,4-dihydroxybenzoate (6)
2,4-Dihydroxybenzoic acid (10g, 64.88mmol) and sulfuric acid (5mL) in MeOH (40mL) was stirred at 100°C for 24h, equipped with a refluxing condenser under argon. After cooling at room temperature, the mixture was concentrated under reduced pressure and added water at 0°C. To filter the resulting white solid was dissolved in ethyl acetate washed with saturated NaHCO3 solution. The organic layer was dried over Na2SO4, concentrated under reduced pressure to afford compound 6 in 86% yield. 1H NMR (500MHz, CD3OD) 7.56 (d, J=9Hz, 1H), 6.24 (dd, J=8.8Hz, 2.0Hz, 1H), 6.21 (d, J=2.5Hz, 1H), 3.78 (s, 3H). 13C NMR (125MHz, CD3OD) δ 171.7, 165.7, 164.9, 132.7, 109.1, 105.5, 103.4, 52.3.

With sulfuric acid for 22h; Heating;
DOI 10.1021/ol070781+

With sulfuric acid for 16h; Reflux;
DOI 10.1016/j.ejmech.2020.112770
Experimental Procedure
Synthesis of Methyl 2,4-dihydroxybenzoate (10).
A solution of 2,4-dihydroxybenzoic acid (9) (20.00g, 129.77mmol) in dry methanol (100mL) and concentrated sulfuric acid (2.6mL) was stirred under reflux for 16h. After reaction completion, the solvent was removed under reduced pressure and the residue was taken up with ethyl acetate. The organic layer was washed with brine, dried over MgSO4 and evaporated in vacuo. Further purification was done with silica gel column chromatography with a mobile phase of n-hexane and ethyl acetate (ratio of 4:1). The desired compound was obtained as a white solid (7.76g, 36%). 1H NMR (250MHz, DMSO-d6): δ 10.70 (s, 1H, OH), 10.44 (s, 1H, OH), 7.64 (d, J=8.7Hz, PhH), 6.37 (dd, J=8.8, 2.4Hz, 1H, PhH), 6.29 (d, J=2.3Hz, 1H, PhH), 3.84 (s, 3H, OCH3) ppm.

[Diman1133]

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