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With o-xylylene bis(triethylammonium tribromide) In acetonitrile at 20℃; for 0.05 h;
General procedure: To a magnetic solution of aromatic compound (1 mmol)in acetonitrile (5 mL), OXBTEATB (0.233 g, 0.5 mmol) wasadded and stirred at room temperature for the appropriatetime (Table 1). The reaction was monitored by TLC (eluent:n-hexane/ethyl acetate: 5/1). The reaction mixture was transferredinto a separatory funnel after filtration of OXBTEABand was extracted with water (15 mL) and dichloromethane(20 mL). The organic layer was dried over anhydrousNa2SO4, and the solvent was concentrated in a rotary evaporator.The crude product was purified by passing it over acolumn of silica gel using a mixture of n-hexane and ethylacetate as the eluent. In order to regenerate the reagent, whitesolid was treated with liquid bromine. All the product structureswere confirmed by comparison of melting point or 1HNMR spectra with ones reported in the literature [29a-29e].
76%
With tetrabuthylammonium tribromide In dichloromethane; water at 20℃; for 2 h;
To a stirred suspension of 2, 5-dimethyl phenol (5.0 g, 40.9 mmol) in H20 (150 mL), at room temperature was added tetrabutylammonium tribromide (19.9 g, 41. 39 mmol) in CHC13 (150 mL). The reaction mixture was stirred for 2 h at rt, the organic layer was separated and dried over Na2S04, filtered and concentrated. The residue was purified by column chromatography on silica gel eluting with hexane-ethyl acetate (1: 5) to afford 2,5-dimethyl-4-bromophenol as a brown solid (6.2 g, 76percent) ; 1H NMR (300 MHz, DMSO-d6) :8 9.47 (s, 1 H), 7.24 (s, 1 H), 6.74 (s, 1 H), 2.21 (s, 3 H), 2.07 (s, 3 H); TLC conditions: Uniplate silica gel, 250 microns; Mobile phase = hexanes-ethyl acetate (9: 1) ; Rf = 0. 52.
76%
With tetra-N-butylammonium tribromide In chloroform; water at 20℃; for 2 h;
To a stirred suspension of 2,5-dimethyl phenol (5.0 g, 40.9 mmol) in H2O (150 mL), at room temperature was added tetrabutylammonium tribromide (19.9 g, 41.39 mmol) in CHCl3 (150 mL). The reaction mixture was stirred for 2 h at rt, the organic layer was separated and dried over Na2SO4, filtered and concentrated. The residue was purified by column chromatography on silica gel eluting with hexane-ethyl acetate (1:5) to afford 2,5-dimethyl-4-bromophenol as a brown solid (6.2 g, 76percent); 1H NMR (300 MHz, DMSO-d6): δ 9.47 (s, 1H), 7.24 (s, 1H), 6.74 (s, 1H), 2.21 (s, 3H), 2.07 (s, 3H); TLC conditions: Uniplate silica gel, 250 microns; Mobile phase hexanes-ethyl acetate (9:1); Rf=0.52.
76%
With tetrabuthylammonium tribromide In dichloromethane; water at 20℃; for 2 h;
To a stirred suspension of 2, 5-dimethyl phenol (5.0 g, 40.9 mmol) in H20 (150 mL), at room temperature was added tetrabutylammonium tribromide (19.9 g, 41. 39 mmol) in CHC13 (150 mL). The reaction mixture was stirred for 2 h at rt, the organic layer was separated and dried over Na2S04, filtered and concentrated. The residue was purified by column chromatography on silica gel eluting with hexane-ethyl acetate (1: 5) to afford 2,5-dimethyl-4-bromophenol as a brown solid (6.2 g, 76percent) ; 1H NMR (300 MHz, DMSO-d6) :8 9.47 (s, 1 H), 7.24 (s, 1 H), 6.74 (s, 1 H), 2.21 (s, 3 H), 2.07 (s, 3 H); TLC conditions: Uniplate silica gel, 250 microns; Mobile phase = hexanes-ethyl acetate (9: 1) ; Rf = 0. 52.
Reference：
[1] Tetrahedron, 2007, vol. 63, # 34, p. 8242 - 8249
[2] Letters in Organic Chemistry, 2018, vol. 15, # 8, p. 682 - 687
[3] Journal of the Chilean Chemical Society, 2011, vol. 56, # 4, p. 863 - 865
[4] Bulletin of the Chemical Society of Japan, 1987, vol. 60, # 11, p. 4187 - 4189
[5] Synthetic Communications, 2010, vol. 40, # 6, p. 868 - 876
[6] Tetrahedron Letters, 2007, vol. 48, # 7, p. 1255 - 1259
[7] Patent: WO2005/51298, 2005, A2, . Location in patent: Page/Page column 243
[8] Patent: US2009/28925, 2009, A1, . Location in patent: Page/Page column 105-106
[9] Russian Chemical Bulletin, 2013, vol. 62, # 6, p. 1395 - 1400[10] Izv. Akad. Nauk, Ser. Khim., 2013, # 6, p. 1395 - 1400,6
[11] Patent: WO2005/51298, 2005, A2, . Location in patent: Page/Page column 243
[12] Journal of the American Chemical Society, 2014, vol. 136, # 50, p. 17434 - 17437
[13] Macromolecules, 2002, vol. 35, # 13, p. 4997 - 5003
[14] Justus Liebigs Annalen der Chemie, 1898, vol. 302, p. 122
[15] Chemische Berichte, 1878, vol. 11, p. 28
[16] DRP/DRBP Org.Chem.,
2
[ 93684-17-4 ]
[ 85223-93-4 ]
Reference：
[1] Journal of the American Chemical Society, 1985, vol. 107, # 2, p. 455 - 459
[2] Journal of the American Chemical Society, 1988, vol. 110, # 10, p. 3226 - 3230
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