p-Toluenesulfonic acid monohydrate → Methyl 4-oxo-4,5,6,7-tetrahydro-1-benzofuran-3-carboxylate

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Reaction Steps

To a solution of 2.11 g of 4-oxo-4,5,6,7-tetrahydrobenzo[b]furan-3-carboxylic acid in 100 ml of methanol is added 202 mg of p-toluenesulfonic acid hydrate and the mixture heated at reflux for 24 hours. The reaction mixture is cooled to room temperature and the methanol concentrated in vacuo to a residue. The residue is dissolved in 100 ml of ethyl acetate and washed with 30 ml of saturated sodium bicarbonate and 30 ml of brine. The organic layer is dried with Na2SO4, filtered and the filtrate concentrated in vacuo to a residue which is crystallized from ethyl acetate-hexane to give 1.75 g of the desired product as a white crystalline solid, m.p. 100°-102° C.

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