Hydrogen Peroxide → 1-(3-Bromo-phenyl)-4-methyl-1h-imidazole

Participants

Reaction Conditions

Reaction Steps

The title compound was prepared from 2-iodo-6-methyl-4-(4-trifluoromethyl-phenyl)pyridine (example A.31) (400 mg, 1.09 mmol) and 4-methyl-1-[3-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-imidazole [in situ prepared by the following sequence: Step 1) A mixture of commercially available 3-bromophenylisothiocyanate (10.06 g, 47.0 mmol) and 2-aminopropionaldehyde dimethylacetal (5.96 mL, 47.0 mmol) in EtOH (50 mL) was refluxed for 1 h. Evaporated to dryness to give 1-(3-bromo-phenyl)-3-(2,2-dimethoxy-1-methylethyl)-thiourea as an off-white solid (15.69 g, 100%). Step 2) A mixture of the above prepared 1-(3-bromo-phenyl)-3-(2,2-dimethoxy-1-methyl-ethyl)-thiourea (15.69 g, 47 mmol) in H2O (85 mL) and 37% HCl (8.5 mL) was refluxed for 4.5 h. Removed from oilbath, added ice and ice water (total volume: 250 mL), the precipitate was filtered off, washed several times with ice water and dried in vacuum at 60° C. to give the 1-(3-bromo-phenyl)-4-methyl-1H-imidazole-2-thiol as a light orange solid (8.71 g, 69%). Step 3) To a suspension of the above prepared 1-(3-bromophenyl)-4-methyl-1H-imidazole-2-thiol (6.00 g, 22 mmol) in acetic acid (20 mL) and water (5 mL) was added dropwise 35% H2O2 (13.4 mL, 156 mmol) within 15 min keeping the internal temperature below 60° C. Stirred at 23° C. for 30 min, poured onto ice, destroyed excess H2O2 by addition of sat. Na2SO3-sol., adjusted pH with 32% NaOH-sol. until pH 9 is reached, extracted with EtOAc (3×100 mL), the combined organic layers were washed with brine and dried over Na2SO4. Removal of the solvent in vacuum left a red oil, which was purified by silica gel column chromatography with EtOAc to give the 1-(3-bromo-phenyl)-4-methyl-1H-imidazole as a brown oil (3.80 g, 72%). Step 4) A mixture of the above prepared 1-(3-bromo-phenyl)-4-methyl-1H-imidazole (0.313 g, 1.31 mmol), bis(pinacolato)diboron (0.364 g, 1.438 mmol), potassium acetate (0.389 g, 3.96 mmol) and PdCl2(PPh3)2 (0.023 g, 3 mol %) in DMF at 100° C. for 2 h; then addition of Pd(OAc)2 (0.007 g, 3 mol %) and dppf (0.018 g, 3 mol %) and stirred at 100° C. overnight. This solution obtained was used directly.] according to the general procedure VI. Obtained as an off-white solid (0.140 g, 32%). MS (ISP) 394.0 [(M+H)+]; mp 126-132° C.

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