2,5-Dichlorobenzoic acid → 2-(2,5-Dichlorophenyl)-1,3-benzoxazole

Participants

Reaction Steps

2,5-Dichlorobenzoic acid (800 g, 4.2 mol), 2-aminophenol (415 g, 3.8 mol) and polyphosphoric acid (1600 g) were placed in a flask and heated at 180°-190° C. for 2 days. The viscous dark solution was poured onto ice while hot. The solid was collected by filtration and washed with water thoroughly. The solid cake was transferred into a large beaker and stirred with 2 liters of saturated aqueous sodium bicarbonate for 16 hours. The brownish suspension was filtered and washed with water and dried at 80° C. overnight to give 1 kg of crude product. The crude product was purified by recrystallization from cyclohexane twice to give 474 g of monomer as white crystals.

Provenance & Evidence