Hydrochloric Acid → 5,6-Dimethoxy-3H-isobenzofuran-1-one

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Reaction Steps

A suspension of 3,4-dimethoxybenzoic acid (10 g, 54.9 mmol) in aqueous 37% HCl (126 ml, 1522 mmol) and a 37% solution in water of formaldehyde (25 ml, 54.9 mmol) were heated to 90 to 100° C. for 6 hours. Stirring was prolonged overnight at room temperature, and then the obtained insoluble material was removed by filtration. The filtrate was quenched with water (200 ml) and extracted with ethyl acetate (200 ml×3). The combined organic layers were washed with aqueous 1N NaOH (100 ml) and then with brine (2×100 ml). The organic phase was dried over Na2SO4, filtered and evaporated to dryness. The obtained yellow solid was triturated with ethyl acetate to afford 5,6-dimethoxyisobenzofuran-1(3H)-one as a white solid (3.171 g, 16.33 mmol, 30% yield). MS/ESI+ 195.0 [MH]+.

Provenance & Evidence