1-[2,4-Dihydroxy-3-(prop-2-en-1-yl)phenyl]ethan-1-one → 2',4'-Dihydroxy-3'-propylacetophenone

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Reaction Steps

The chromone derivative of formula I is readily prepared according to the following reaction scheme: ##STR2## by reacting 2,4-dihydroxyacetophenone (II) with allylbromide in the presence of potassium carbonate and acetone to obtain 4-allyloxy-2-hydroxyacetophenone III which, upon heating at 180°-220° C., undergoes rearrangement to form 3-allyl-2,4-dihydroxyacetophenone (IV). The dihydroxy intermediate then is catalytically reduced in the presence of palladium/carbon catalyst to form 2,4-dihydroxy-3-propylacetophenone (V). Intermediate (V) then is treated with epichlorohydrin in refluxing ethanolic potassium hydroxide to form 4-(2,4-epoxypropoxy)-2-hydroxy-3-propylacetophenone (VI) and with diethyl oxalate in the presence of sodium ethoxide to form ethyl 7-hydroxy-8-propyl-4-oxo-4H-1-benzopyran-2-carboxylate (VII). Intermediates (VI) and (VII) are reacted under a nitrogen atmosphere at 140°-150° C. in the presence of Triton B (Rohm & Hass, Philadelphia, Pa.) and the resulting ester treated with sodium bicarbonate to form 7-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-2-hydroxypropoxy]-4-oxo-8-propyl-4H-1-benzopyran-2-carboxylic acid (VIII). This intermediate, preferrably the sodium salt, then is iodinated in the presence of potassium triiodide to form the desired 7-[3-(4-acetyl-3-hydroxy-6-iodo-2-propylphenoxy)-2-hydroxypropoxy]-4-oxo-8-propyl-4H-1-benzopyran-2-carboxylic acid (I).

Provenance & Evidence