Sulfuric Acid → Methyl 5-methyl-2-thiophenecarboxylate

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5-Methyl-2-thiophene carboxylate (2.0 g, 14.1 mmol, Aldrich, 1001 West Saint Paul Avenue, Milwaukee, Wis. 53233 USA) was carefully dissolved in 50 ml methanol and 15 ml conc. sulfuric acid at room temperature under an inert atmosphere. The reaction mixture was refluxed at 83° C. for 5 hours. After the reaction mixture was allowed to cool to room temperature, it was poured into a beaker containing 200 ml of ice. This aqueous mixture was neutralized to pH 7 with solid NaHCO3. This liquid was poured into a separatory funnel and extracted 2×200 ml CH2Cl2. The combined organics were dried over MgSO4, filtered, and stripped to provide the title compound of this Preparation (2.2 g, 67% yield) as a brown oil. 1H NMR (CDCl3): δ 7.61 (1H, d J=4), 6.77 (1H, d, J=4), 3.84 (3H, s), 2.52 (3H, s).

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