A.
Ethyl 2,5-dimethylphenylhydroxymalonate.
One hundred and seventy-four grams (1 mole) of ethyl oxomalonate (Note
1) and
265 g. (2.5 moles) of p-xylene are mixed in a
1-l. three-necked flask equipped with a
good stirrer, a
dropping funnel, and a
calcium chloride drying tube. Suitable precautions are taken to exclude moisture from the reaction mixture. While the mixture is cooled in an
ice-water bath and stirred vigorously,
325 g. (1.25 moles) of anhydrous stannic chloride is added dropwise from the funnel. After the addition is complete, the cooling bath is removed and stirring is continued for 3 hours. The reaction mixture is poured with stirring into about 300 g. of cracked ice containing
50 ml. of concentrated hydrochloric acid. On standing this mixture separates into two layers. Two hundred milliliters of
ether is added, and the
ether layer is washed with 100-ml. portions of water until the wash water is free from chlorides. The
ether solution is dried with anhydrous
sodium sulfate and distilled. After removal of the
ether and the excess of reagents (Note
2), the fraction boiling at
154–156°/5 mm. is collected. The yield of
2,5-dimethylphenylhydroxymalonic ester is
144.5–160 g. (
51.5–57%).