Ethylene Glycol → 2-Butyl-4-carbethoxy-5-methyl-2,3-dihydrofuran

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A mixture containing 750 grams of 3-acetyl-5-butyl-dihydro-2 (3H)-furanone (4.0 mols), 750 grams of cyclohexane and 8.6 grams of sodium hydrogen sulfate were heated to reflux. To the refluxing mixture were added 250 grams of ethylene glycol (4.0 mols) over a period of 6 hours while the water formed by the reaction was collected in a Dean Stark Trap. An additional 110 grams of ethylene glycol (1.8 mols) was added over 22 hours to replace glycol carried over with the refluxing cyclohexane (azeotropic agent). After 36 hours, an analysis of the reaction mixture showed that the furanone was 95.4 percent converted to a ketal of the formula ##STR21## An aliquot of 94.5 grams of the mixture (0.22 mols) and 30.5 grams of anhydrous ethanol (0.66 mols) and 0.6 grams of p-toluene sulfonic acid were refluxed at 71° C. for 26 hours. The mixture was then neutralized with 0.73 grams of sodium ethoxide followed by stripping on a Rotovap under vacuum to a temperature of 90° C. The residue was water washed, dried on a Rotovap and distilled to provide 29.6 grams of 2-butyl-4-carbethoxy-5-methyl-2,3-dihydrofuran. The amount of recovered material represented a yield of 63.5 percent based on the amount of furanone reacted and a yield of 66.9% based on a 93.0% conversion of the ketal.

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