Carbon Dioxide → 7-hydroxy-5-methylcoumarin

Participants

Reaction Steps

5-methylresorcinol monohydrate (284 gm, 2.0 mol; Aldrich) was thoroughly mixed with malic acid (280 gm, 2.10 mol; Aldrich) and then placed in a reaction flask containing sulfuric acid (600 ml) and a trace of sodium bisulfite (1.0 gm; Aldrich). The reaction mixture was heated to 90.C while being mechanically stirred until evolution of carbon dioxide subsided (about 5 hours). The resulting reddish-orange solution was poured into sufficient ice (with vigorous stirring) to make up 1 liter. The receiving flask was maintained at 0.C by external cooling until the addition of the reaction mixture was complete. The resulting light-orange product that precipitated was collected by suction filtration then washed thoroughly with water. The crude product was air dried on the filter, then recrystallized twice from tetramethylene glycol (1800 ml) to give pure 7-hydroxy-5-methylcoumarin (H5MC,l) as product (220 gm, 62% yield; mp 252°-255° C.).

Provenance & Evidence