Boron tribromide → 2-(5-Oxazolyl)phenol

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Reaction Steps

A mixture of 2-methoxybenzaldehyde (10.0 g, 73.4 mmol), tosylmethylisocyanide (14.34 g, 73.4 mmol) and potassium carbonate (10.14 g, 73.4 mmol) in 220 ml methanol is heated at reflux for 6 hours. The solvent is removed under reduced pressure and the residue poured into ice-water (800 ml). The precipitate is collected by filtration, washed with water, and dried in vacuo to give 9.05 g of 5-(2-methoxyphenyl)oxazole (70%). Boron tribromide (1M in dichloromethane, 36 ml) is added slowly to a cold solution (0° C.) of the above oxazole (3.0 g, 17.1 mmol) in dichloromethane (215 ml). After stirring overnight at room temperature, ice-water (50 ml) is added carefully. The aqueous layer is extracted with dichloromethane (50 ml), and the combined organic layers are dried over sodium sulfate and concentrated under reduced pressure. The precipitate which formed after addition of dichloromethane (70 ml) is collected by filtration, heated with dichloromethane (15 ml), and filtered again to give 3.16 g of 2-(5-oxazolyl)phenol. This phenolic product is reacted with (2S)-glycidyl 3-nitrobenzenesulfonate substantially as described for Epoxide 1 to give 400 mg of the title epoxide (9.5%).

Provenance & Evidence