(r)-2,2,6-三甲基-1,4-环己二酮

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C. under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C. under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: A mixture of (-)-(6R)-2,2,6-trimethyl-1,4-cyclohexandione (924 mg, 6.0 mmol), 2,2-dimethyl-1,3-propandiol (791 mg, 7.6 mmol), pyridinium p-tosylate (34 mg, 0.13 mmol), and benzene (15 mL) was heated to reflux under a Dean-Stark water separator for 4 h. The reaction mixture was allowed to cool to room temperature before it was washed with H2O, and dried over anhydrous Na2SO4. Evaporation of solvent gave a pale yellow oil (1.43 g) as the crude product, which was distilled using the Kugel-rohr apparatus (80°-100° C., 0.03 mm Hg) to give pure ketal as a colorless oil (1.31 g, 91%), [a]D -87.7° C. (c 1.10, CH3OH); ir: 1710 cm-1; 1H nmr d: 0.85 (s, 3H, CH3), 0.91 (d, J=6.6 Hz, 3H, CHCH3), 0.97 (s, 6H, 2 CH3), 1.16 (s, 3H, CH3), 1.56 (dd, J=13.5, 13.5 Hz, H-11ax), 1.58 (d, J=14.2 Hz, H-7ax), 2.38 (ddd, J=13.5, 5.3, 3.8 Hz, 1H, H-11eq), 2.47 (dd, J=14.2, 3.8 Hz, 1H, H-7eq), 2.85 (m, 1H, CHCH3), 3.41 and 3.48 (2dd, J=11.4, 1.6 Hz, 2H, 2 equatorial H at C2 and C4), 3.53 and 3.61 (2d, J=11.4 Hz, 2H, 2 axial H at C2 and C4); ms m/e: 240 (M+, 0.58), 141 (27), 155 (98), 83 (27), 69 (100). was heated was washed with H2O dried over anhydrous Na2SO4 Evaporation of solvent

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C. under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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 produce 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C. under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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 produce 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C. under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: A mixture of (-)-(6R)-2,2,6-trimethyl-1,4-cyclohexandione (924 mg, 6.0 mmol), 2,2-dimethyl-1,3-propandiol (791 mg, 7.6 mmol), pyridinium p-tosylate (34 mg, 0.13 mmol), and benzene (15 mL) was heated to reflux under a Dean-Stark water separator for 4 h. The reaction mixture was allowed to cool to room temperature before it was washed with H2O, and dried over anhydrous Na2SO4. Evaporation of solvent gave a pale yellow oil (1.43 g) as the crude product, which was distilled using the Kugel-rohr apparatus (80°-100° C., 0.03 mm Hg) to give pure ketal as a colorless oil (1.31 g, 91%), [a]D -87.7° C. (c 1.10, CH3OH); ir: 1710 cm-1; 1H nmr d: 0.85 (s, 3H, CH3), 0.91 (d, J=6.6 Hz, 3H, CHCH3), 0.97 (s, 6H, 2 CH3), 1.16 (s, 3H, CH3), 1.56 (dd, J=13.5, 13.5 Hz, H-11ax), 1.58 (d, J=14.2 Hz, H-7ax), 2.38 (ddd, J=13.5, 5.3, 3.8 Hz, 1H, H-11eq), 2.47 (dd, J=14.2, 3.8 Hz, 1H, H-7eq), 2.85 (m, 1H, CHCH3), 3.41 and 3.48 (2dd, J=11.4, 1.6 Hz, 2H, 2 equatorial H at C2 and C4), 3.53 and 3.61 (2d, J=11.4 Hz, 2H, 2 axial H at C2 and C4); ms m/e: 240 (M+, 0.58), 141 (27), 155 (98), 83 (27), 69 (100). was heated was washed with H2O dried over anhydrous Na2SO4 Evaporation of solvent

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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 crystallized 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 crystallized overnight at 5° C filtered off under suction washed twice with 1500 ml of cold n-hexane each time dried for 15 hours at 40° C under reduced pressure This first crystallisation

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 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. The solvent phase is separated washed twice with 60 liters of water each time concentrated to about 15 liters on a rotary evaporator filtered concentrated to dryness under reduced pressure The residue (1755 g) is dissolved while hot in 6 liters of diisopropyl ether filtered over diatomaceous earth padding 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 dried for 15 hours at 40° C under reduced pressure This first crystallisation