Phosphoric Acid → 5-(4-Methoxyphenyl)-2-(pyridin-4-yl)oxazole

Participants

Reaction Steps

Isonicotinic acid (24.93 g., 0.0938 mole) and thionyl chloride (50 ml) is refluxed for 1 hour. The crude acid chloride which remains after removal of excess thionyl chloride at diminished pressure is dissolved in dry pyridine (200 ml) and p-methoxy phenacylammonium chloride (19.00 g, 0.938 mole) is added portion wise to the stirred solution. The addition is exothermic.. After the addition is completed, the reaction mixture is heated and stirred on a boiling water bath for 2 hours and then poured into ice-water to precipitate the product. The solid is collected and dried under reduced pressure to give α-isonicotinamido-p-methoxyacetophenone m.p. 227°-230° C. (with decomposition). α-isonicotinamido-p-methoxyacetophenone (11.5 g., 0.043 mole) is added portion-wise to a stirred solution of 200 ml of acetic anhydride and 15 ml of 90% phosphoric acid; the addition is exothermic. After the addition is complete the reaction mixture is stirred and refluxed for 2 hours. After cooling, the supernatant liquid is decanted from the viscous precipitate, which is crystallized by titration with 350 ml of 1% aqueous sodium hydroxide. The yellow solid is filtered, washed with distilled water (200 ml), and dried in vacuo yielding 2-(4-pyridyl)-5-p-methoxyphenyloxazole, m.p. 105°-107° C.

Provenance & Evidence