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A 1 l. three-necked flask, equipped with a dropping funnel, mechanical stirrer and a distillation head with thermometer and Liebig condenser was charged with 515 ml of xylene (b.p. 138°-140°), stirred and heated to boiling. 65.9 g of a 24% (wt/wt) sodium methoxide solution (prepared as in Example 1) in methyl alcohol (15.8 g = 0.293 moles) was added over 10 min., distilling off continuously the methyl alcohol. 300 ml of additional xylene were added and distillation was continued until the vapor temperature reached 135°. After the addition of 6.6 ml of dimethylsulfoxide, a solution of 40 g (0.232 moles) of 4-oxoheptanoic acid ethyl ester in 80 ml of xylene was added over 25 min. to the vigorously stirred sodium methoxide suspension while keeping the vapor temperature at ca. 135°C by continuous distillation of xylene. The orange-colored mixture was stirred and heated for an additional 5 min. and then allowed to cool to room temperature. Water was added, the mixture was acidified and the product filtered, washed, dried and recrystallized from water to afford 13.45 g (46%) of 2-ethyl-cyclopentan-1,3-dione, m.p. (uncorr.): 171°-172°C.

1. customthree-necked flask, equipped with a dropping funnel, mechanical stirrer
2. temperatureheated to boiling
3. distillationdistilling off continuously the methyl alcohol
4. addition300 ml of additional xylene were added
5. distillationdistillation
6. customreached 135°
7. additionAfter the addition of 6.6 ml of dimethylsulfoxide
8. customat ca. 135°C
9. distillationby continuous distillation of xylene
10. stirringThe orange-colored mixture was stirred
11. temperatureheated for an additional 5 min.
12. additionWater was added
13. filtrationthe product filtered
14. washwashed
15. customdried
16. customrecrystallized from water