Diphenyl Ether → 5,7-Dichloro-4-hydroxy-quinoline-2-carboxylic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

A 5-L three-neck flask equipped with a thermocouple, an addition funnel, and a distillation apparatus was charged with diphenyl ether (about 2.8 L), which was heated to about 244° C. The concentrated reaction mixture containing Compound 3 (about 1.1 mole) from Reaction 1, above, was added from the dropping funnel into the hot diphenyl ether over about 10 minutes with a nitrogen purge. The funnel was rinsed with about 200 mL of diphenyl ether, which was also added to the flask. The resulting mixture was heated at about 244° C. for about 1 hour to cyclize Compound 3 to form Compound 4. The reaction mixture then was cooled to room temperature, at which point Compound 4 crystallized out. The crystallized product was isolated and slurried with ethyl acetate (EtOAc; about 1 L). The crystals were collected and rinsed with EtOAc (3×500 mL), and then dried under high vacuum at room temperature to afford about 269.95 g of Compound 4 (85.8% yield over two steps).

Provenance & Evidence