Maleic Anhydride → 4-Methyl-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1,3-dione

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Reaction Steps

2-Methyl furan was reacted with maleic anhydride in a manner similar to the procedure described in Example 1 to yield 1-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride. An amount of 28 mmol of this compound was dissolved in methanol (50 ml). To this solution, solid sodium methoxide (56 mmol) was added at 0° C. The resulting deep orange solution was stirred for 18 h at room temperature, after which the solvent was evaporated in vacuo. After drying for 1 h at 77° C. under reduced pressure, the solid was dissolved in water and heated under reflux for 5 h followed by treatment with charcoal (stirring for 30 min at reflux). Filtration and evaporation under reduced pressure yielded 3-methylphthalic acid disodium salt (4.4 g, 71%).

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