3-Hydroxyanthranilic Acid → 2-p-Tolylbenzoxazole-4-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

To a suspension of 3-hydroxyanthranilic acid (0.153 g, 1 mmol) in toluene (10 mL) was added 4-methylbenzoylchloride (0.464 g, 3 mmol) followed by pyridine (0.275 g, 3.5 mmol) at room temperature. The resulting mixture was stirred at room temperature for 30 minutes then heated to 80C for 1 hr. After this time the reaction was cooled and poured into a mixture of ethyl acetate (50 mL) and 5% aqueous hydrochloric acid (20 mL). Subsequent separation of the layers, drying the organic over MgSO4 and filtration afforded a solution. After removal of the solvent, the residue was dissolved in xylenes (20 mL) and the solution treated with p-TsOH (0.4 g, 2.1 mmol). The reaction mixture was then heated to reflux overnight. After this time the reaction was cooled and poured into water (100 mL), the organic layer separated then washed with water (100 mL). The organic was dried over MgSO4, filtered and concentrated to a solid. Recrystallization of this solid from ethyl acetate gave a white solid product, 2-p-tolylbenzo[d]oxazole-4-carboxylic acid (0.15 g, 60% yield). MS (ESI) m/e 254 [M+H]+.

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