Ethanol → 5-(tert-Butyl)oxazole-2-carboxylic acid

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Reaction Steps

A solution of sodium hydroxide (0.96 g, 24 mmol) in water (25 ml) is added to a stirred solution of 5-tert-butyl-oxazole .2-carboxylic acid ethyl ester (3.94 g, 20 mmol) In ethanol (35 ml), and the mixture is warmed to 60° C. and stirred for 1 h. The ethanol is then removed by distillation and the aqueous residue is washed with diethyl ether and acidified with 5 N hydrochloric acid. The resulting precipitate is collected by filtration and dried to give 5-tert-butyl-oxazole-2-carboxylic acid (2.30 g, 68%) as beige crystals. This material is used immediately without further purification since, on prolonged storage, it undergoes spontaneous decarboxylation to 5-tert-butyl-oxazole.

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