Ketoisophorone → Levodione

참여 물질

반응 단계

The water phase (190 liters+5 liters of wash-water) is stirred out five times with 60 liters of methylene chloride each time. The solvent phase is separated, washed twice with 60 liters of water each time and concentrated to about 15 liters on a rotary evaporator. This concentrate is dehydrated with 1.5 kg of sodium sulphate, filtered and concentrated to dryness under reduced pressure. The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether, decolourised with 80 g of active carbon, filtered over diatomaceous earth padding and rinsed with 1.8 liters of hot diisopropyl ether. From this solution, 2.6 liters of diisopropyl ether are distilled off at normal pressure, such that the product remains dissolved in a three-fold amount of diisopropyl ether. The product is crystallised overnight at 5° C., filtered off under suction, washed twice with 1500 ml of cold n-hexane each time and dried for 15 hours at 40° C. under reduced pressure. This first crystallisation produces 1280 g of optically pure [6R]-2,2,6-trimethyl-1,4-cyclohexanedione of melting point 91°-92° C. The mother liquor contains a further 447 g of substances. The latter is taken up in the same amount of n-hexane, treated with diisopropyl ether until the solution is clear, crystallised overnight at 5° C., filtered off under suction and washed twice with a small amount of cold n-hexane. The crystallisate is dried at 40° C. under reduced pressure. This second crystallisation produces 83.6 g of product with a melting point of 70°-88° C. After triple recrystallisation with the three-fold amount of diisopropyl ether, there are obtained a further 43 g of optically pure [6R]-2,2,6 -trimethyl-1,4-cyclohexanedione of melting point 90.5°-91.5° C.

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