Scientia Sinica

54 SCIENTIA SINICA Vol. V

solution was washed twice with 5% sodium bicarbonate and twice with water and then it was dried over anhydrous magnesium sulfate. After the removal ot the solvent at reduced pressure, the low boiling fraction was quickly distilled off at 0.2 mm in an oil bath of 150°. The yellow oily residue was directly used for the following experiment without further purification. The crude product amounted to 160 g.

y-(6-Methoxy-2-carboxy-3, 4-dihydro-l-naphthyl)-butyric Acid (VII).This compound was prepared according to the method of Bachmann and coworkers! with two major modifications: (1) The keto malonic ester (V) used by Bachmann and coworkers had been purified by flash distillation, but we have found that by cyclizing the crude substituted keto malonic ester as obtained in the above experiment better results could always be obtained. (2) We used two different cyclizing agents, both of which are suitable for making larger runs. Our methods of cyclizing the keto malonic ester (V) are as: follows:

(1) With anhydrous hydrofluoric acid as cyclizing agent—One hundred grams of the crude keto malonic ester (V) was placed in a 1000-ml platinum beaker which was cooled to a temperature of -10 to -15° with ice-salt mixture. To this well-cooled keto malonic ester, about 500 ml of liquid anhydrous hydrofluoric acid was added. After the reaction mixture was kept at about (-10°) for 8 hours, the temperature was gradually raised to room temperature. ‘The hydrofluoric acid was blown off with air. To the residue, about 400 g of cracked ice was added. After the mixture was neutralized with solid sodium carbonate, it was extracted three times with ether, 300 ml being used each time. The ether was distilled off and a solution of the residue in 400 ml of 9572 ethyl alcohol and 200 ml of 45% potassium hydroxide was refluxed for 4 hours. After the major portion of the ethyl alcohol had been removed, the turbid solution was extracted once with ether to remove the small amount of oily substance. Then the clear yellow aqueous solution was slowly poured into 300 ml of concentrated hydrochloric acid and the tribasic acid was liberated as an oil. This oil was extracted three times with ether, 300 ml being used each time. After the ether was distilled off, 500 ml of water was added to the dark oily residue. Vigorous evolution of carbon dioxide took place while the mixture was heated on a steam bath during the first few hours. After the mixture had been heated on the steam bath for twelve hours, it was cooled, and the oily tribasic acid changed to semi-solid dibasic acid upon losing carbon dioxide. This was filtered and the semi-solid, after trituration with 50 ml of ether, 34 g of colourless solid was obtained; m.p. 182-188° (with decomposition). The yield was 47% based on B-m-anisylethylmalonate while the yield was only 27% using the method of Bachmann and coworkers)". The crude acid, after recrystallization from benzene-dioxane, formed colourless needles; m.p. 188-190° (with decomposition) alone or when mixed with a sample prepared by Bachmann and coworkers.