Hydrogen Bromide → 5-Bromo-2,2,3,3-tetrafluorobenzofuran

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Reaction Conditions

Reaction Steps

A stirred mixture of 5-amino-2,2,3,3-tetrafluorobenzofuran (5.0 g, 0.024 mole) and hydrobromic acid (7.3 ml of a 48% aqueous solution) and water (10 ml) was cooled to 3° C. in an ice bath. While maintaining a temperature of less than 5° C., a solution of sodium nitrite (1.7 g, 0.024 mole) in water was added. After complete addition this mixture was stirred for a brief period, then was added slowly to a stirred, refluxing mixture of cuprous bromid (6.9 g, 0.024 mole) in hydrobromic acid (10 ml of a 48% aqueous solution). After complete addition the mixture was stirred at reflux for 20 minutes, then allowed to cool to room temperature. The reaction mixture was poured into a separatory funnel and diluted with ice water. This mixture was extracted several times with diethyl ether. The extracts were combined and washed first with 100 ml of an aqueous saturated sodium chloride solution, then with two 100 ml portions of a 2 N aqueous sodium hydroxide solution. The washed organic phase was dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated at atmospheric pressure, yielding 5.9 g of 5-bromo-2,2,3,3-tetrafluorobenzofuran as an oil.

Provenance & Evidence