Toluene → Methyl 4,4-ethylenedioxy-1,2,3,4-tetrahydro-5,8-dimethoxynaphthalene-2-carboxylate

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Reaction Steps

40 g of methyl rac-1,2,3,4-tetrahydro-5,8-dimethoxy-4-oxonaphthalene-2-carboxylate were added to a mixture of 800 ml of toluene, 800 ml of hexane, 30 ml of ethyleneglycol and 0.65 g of toluene-4-sulphonic acid. The mixture was heated under reflux for 24 hours using a Dean-Stark trap. The solution was cooled in an ice-bath and washed with three 124 ml portions of 10% potassium hydrogen carbonate solution and 200 ml of brine, dried and the solvent was evaporated. The residue was taken up in 200 ml of methanol at 70° C. and 0.5 g of a 50% dispersion of sodium hydride in mineral oil was added. The solution obtained was left to cool to room temperature and then cooled further in an ice-bath for 2 hours. The crystalline product was filtered off, washed with cold methanol and dried in vacuo. There were obtained 28.5 g (61%) of methyl rac-4,4-ethylenedioxy-1,2,3,4-tetrahydro-5,8-dimethoxynaphthalene-2-carboxylate in the form of colourless crystals of melting point 133°-134° C.

Provenance & Evidence