Benzyl Bromide → 1-Benzyl-2,5,6-trichlorobenzimidazole

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Reaction Steps

2,5,6-Trichlorobenzimidazole (5, 50 mg, 0.0002 moles) was dissolved in 15 ml of CH3CN, and K2CO3 (33 mg, 0.0002 moles) was added. The mixture was stirred at room temperature for one hour, at which time benzyl bromide (0.024 ml, 0.0002 moles) was added. The mixture was then stirred for two days. TLC analysis showed the formation of a new compound with a higher Rf than starting material. The mixture was then concentrated and a liquid-liquid extraction was done using CHCl3, and H2O. The CHCl3 layer was kept, dried with MgSO4, filtered, and then concentrated. Column chromotograpy was then performed using 2% MeOH/CHCl3 to elute the compounds. The fractions were collected and those containing the compound were concentrated. The compound was recrystallized from MeOH, giving 50 mg of 1-benzyl-2,5,6-trichlorobenzimidazole (181) (96.2%). 1H NMR (CDCl3): d 3.49ppm (s, 3H), 7.13 (m, 2H), 7.32 (m, 4H), 7.78 (s, 1H). 13C NMR (CDCl3): d 43.20 ppm, 106.25, 115.78, 121.62, 122.24, 122.66, 123.50, 124.15, 129.05, 129.16, 135.97, 137.68. GC-MS: m/e 310, 273, 239, 221,197, 170, 158, 138, 120, 100,91, 77, 65, 51, 39. m.p: 175°-176° C. Elemental Analysis: (C14H9Cl3 N2): Calculated: C, 53.85; H, 2.88; N, 8.97. Found: C, 53.92; H, 2.85; N, 8.89. UV Imax nm (e×104): (pH 7) 263 (0.080), 290 (0.102), 299 (0.154); (pH 1), 224 (0.412), 258 (0.157),290 (0.155), 299 (0.168).

Provenance & Evidence