Phosphorus oxychloride → Benzoxazole

A solution of 2-bromo-4-chloro-6-(3,5-di-t-butyl-4-hydroxy-phenylacetyl-amino)-phenol (35.67 g, 76.1 mmol) and phosphorus oxychloride (41.8 ml, 457 mmol) in toluene was heated under reflux for 1 hour. Volatiles were removed in-vacuo and residual amounts of phosphorus oxychloride removed by azeotropic distillation with toluene (2×50 ml). The residue was taken up in acetone (50 ml) and ether (100 ml), and treated with water (100 ml) and saturated aqueous sodium bicarbonate solution (100 ml). The organic solvents were removed in-vacuo and the precipitate collected to give 33.36 g (93.6%) of crude benzoxazole. The crude benzoxazole was dissolved in dichloromethane (100 ml), filtered, and the filtrate diluted with methanol (100 ml). The dichloromethane was removed by distillation and the resulting crystals collected, washed, and dried in-vacuo to give 28.86 g (80.9%) of the title compound (mp 133-6° C.).

1. temperatureunder reflux for 1 hour
2. customVolatiles were removed in-vacuo and residual amounts of phosphorus oxychloride
3. customremoved by azeotropic distillation with toluene (2×50 ml)
4. additionether (100 ml), and treated with water (100 ml) and saturated aqueous sodium bicarbonate solution (100 ml)
5. customThe organic solvents were removed in-vacuo
6. customthe precipitate collected

ORD record

ord-88dccea49edc4474bf390f4b70e99bd5

Source dataset

uspto-grants-2002_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06372770B1