Hydrochloric Acid → 2-tert-Butyl-7-nitro-6-phenyl-1,3-benzoxazole-4-carboxylic Acid

Participants

Reaction Conditions

Reaction Steps

6-Bromo-2-tert-butyl-7-nitro-1,3-benzoxazole-4-carboxylic acid (I-222) (2.15 g, 6.27 mmol), phenylboronic acid (1.53 g, 12.53 mmol) and aqueous 2 M sodium carbonate solution (20 ml) were suspended in toluene (40 ml) and ethanol (30 ml). Tetrakis(triphenylphosphine)palladium(0) (724 mg, 0.63 mmol) was added at room temperature to the suspension. The mixture was stirred at 85° C. for 22 hours, then cooled to room temperature. The reaction liquid was fractionated with ethyl acetate and aqueous 1 M hydrochloric acid solution. The organic layer was washed with saturated brine, and dried over anhydrous sodium sulfate. The insoluble matter was removed by filtration, the solvent was evaporated away and the resulting residue was purified by middle-pressure liquid chromatography (eluent, chloroform:methanol=9:1) to obtain the entitled compound (3.00 g) as a brown gel. This was used in the next reaction as such.

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