Hydrochloric Acid → 2-(2-Bromo-5-chlorophenyl)-4,4-dimethyl-4,5-dihydrooxazole

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Reaction Steps

To a suspension of 2-bromo-5-chlorobenzoic acid (1.5 g, 6.4 mmol) in methylene chloride (15 mL) at room temperature was added oxalyl chloride (969 mg, 666 μL, 7.64 mmol) and 2 drops of dimethylformamide; bubbling commenced and the mixture ultimately became homogenous. The mixture was stirred at room temperature for 7 hours and concentrated. The resulting acid chloride residue was dissolved in methylene chloride (15 mL). Triethylamine (325 mg, 450 μL, 3.2 mmol) was added, followed by 2-amino-2-methyl-1-propanol (627 mg, 672 μL, 7.04 mmol) and the reaction was allowed to stir at rt 3 h. The mixture was poured into 1 N hydrochloric acid (50 mL), extracted with methylene chloride (2×75 mL). The combined extracts were washed with saturated aqueous sodium bicarbonate, brine and dried over magnesium sulfate, filtered and concentrated and dried in vacuo. The crude amide residue was dissolved in methylene chloride (15 mL) and thionyl chloride (1.29 g, 794 μL, 10.9 mmol) was added. Stirring at room temperature was carried out for 4 h after which the mixture was poured into saturated sodium bicarbonate (50 mL). The pH was adjusted to 9 by the addition of solid sodium bicarbonate and further basified by the addition of several milliliters of aqueous sodium hydroxide (5 N). The biphasic mixture was extracted with methylene chloride (150+50 mL). The combined extracts were washed with brine, dried over magnesium sulfate, filtered and concentrated to afford the crude residue which was purified by silica gel chromatography (80% hexanes/20% ethyl acetate gradient) to yield 2-(2-bromo-5-chloro-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole (1.15 g, 62%).

Provenance & Evidence