P-Toluic Acid → 4-Methylbenzoyl Chloride

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Reaction Steps

4-methylbenzoic acid (0.408 g, 3 mmol) was dissolved in thionyl chloride (10 mL) and the mixture was stirred at reflux for 6 hr. The mixture was condensed under vacuum to yield 4-methylbenzoyl chloride. To a suspension of 3-hydroxyanthranilic acid (0.153 g, 1.0 mmol) in toluene (10 mL) was added 4-methylbenzoyl chloride (0.464 g, 3.0 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 80° C. for 1 hr. The mixture 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 anhydrous magnesium sulfate and filtration afforded a solution. After removal of the solvent, the residue was dissolved in toluene (20 mL) and the solution treated with 4-methylbenzenesulfonic acid (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 was separated then washed with water (100 mL). The organic phase was dried over anhydrous magnesium sulfate, filtered and concentrated to get a solid. Re-crystallization of this solid from ethyl acetate gave 2 p-tolybenzo[d]oxazole-4-carboxylic acid as a white solid (0.15 g, 60% yield). LC-MS (ESI) m/z 254 [M+1]+.

Provenance & Evidence