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A solution of isopropyl magnesium chloride in ether is prepared by dropwise adding a solution of 410 grams (3.45 moles) of isopropyl chloride in 700 ml of dry ether to a stirred slurry of 76.5 grams of magnesium (3.15 moles) in 600 ml of dry ether under nitrogen at reflux. The resulting solution is stirred at reflux for 30 minutes. A solution of 372 grams of 4-methyl-3-cyclohexenecarboxaldehyde (3.38 moles) in 200 ml of ether is then added to the reaction mixture over a period of 1 hour at reflux under nitrogen. The resulting slurry is heated at reflux for 30 minutes and then cooled to 0° C. 1200 grams of 20% sulfuric acid is slowly added with external cooling over a 30 minute period. After the addition is complete, two clear layers appear. A distillation head is placed on the flask ether is distilled from the reaction mixture at atmospheric pressure to a pot temperature of 90° C. 500 ml of water and 300 ml of isopropyl alcohol is added to the reaction mixture. Sulfuric acid (200 grams) is added slowly and the resulting solution is heated to reflux for 9 hours. At the end of this period the reaction mass is cooled. 500 ml of water and 200 ml of toluene is added thereto with stirring. The phases are allowed to separate and the aqueous phase is discarded. The organic phase is washed twice with H2O, with sufficient sodium carbonate added to the second wash to adjust to pH to 7-8. Distillation of the organic layer affords 255 grams of 3-isopropyl-1-methyl-2-oxabicyclo[2.2.2]octane.

1. temperatureat reflux
2. temperatureat reflux for 30 minutes
3. temperatureat reflux under nitrogen
4. temperatureThe resulting slurry is heated
5. temperatureat reflux for 30 minutes
6. temperaturewith external cooling over a 30 minute period
7. additionAfter the addition
8. distillationis distilled from the reaction mixture at atmospheric pressure to a pot temperature of 90° C
9. addition500 ml of water and 300 ml of isopropyl alcohol is added to the reaction mixture
10. additionSulfuric acid (200 grams) is added slowly
11. temperaturethe resulting solution is heated
12. temperatureto reflux for 9 hours
13. temperatureAt the end of this period the reaction mass is cooled
14. addition500 ml of water and 200 ml of toluene is added
15. stirringwith stirring
16. customto separate
17. washThe organic phase is washed twice with H2O, with sufficient sodium carbonate
18. additionadded to the
19. washsecond wash
20. distillationDistillation of the organic layer