Hydrochloric Acid → Methyl 3-hydroxy-4,5-dimethylthiophene-2-carboxylate

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Reaction Steps

Dry hydrogen chloride gas was bubbled through a mixture of ethyl 2-methyl-3-oxobutanoate (7.6 g, 50 mmol) and methyl 2-mercaptoacetate (11.2 g, 100 mmol) at -10° C. until saturated. The oil was allowed to stand for 3 hours at room temperature, diluted with dichloromethane and washed with brine. After drying with sodium sulphate and evaporation of solvent the oil was dissolved in methanol (10 ml) and added dropwise to methanolic potassium hydroxide (2N; 75 ml), stirring at room temperature for 1 hour. The solution was diluted with iced water (125 ml) and acidified with 3N hydrochloric acid at -3° to 0° C. to pH1. The precipitate was filtered and washed with water (5.5 g, m.p. 50°-51° C., methanol).

Provenance & Evidence