Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D489/00—Heterocyclic compounds containing 4aH-8, 9 c- Iminoethano-phenanthro [4, 5-b, c, d] furan ring systems, e.g. derivatives of [4, 5-epoxy]-morphinan of the formula:
  • C07D489/02—Heterocyclic compounds containing 4aH-8, 9 c- Iminoethano-phenanthro [4, 5-b, c, d] furan ring systems, e.g. derivatives of [4, 5-epoxy]-morphinan of the formula: with oxygen atoms attached in positions 3 and 6, e.g. morphine, morphinone

Definitions

• This invention relates to the preparation of codeine from morphine and, more particularly, to an improved process for the preparation of codeine which provides for more complete control over the formation of the methylated by-product codeine methyl ether and for a more thorough separation of dimethylaniline and codeine.
• Codeine is widely used as an analgesic and is the methyl ether of morphine. While it occurs naturally in opium to a small extent, it has been prepared synthetically by methylation of the phenolic hydroxyl group in morphine.
• codeine by the reaction of morphine with a methylating agent such as dimethyl sulfate or trimethylphenyl ammonium ethoxide or trimethylphenyl ammonium hydroxide in the presence of a base such as aqueous sodium hydroxide, or alcoholic sodium ethoxide.
• a methylating agent such as dimethyl sulfate or trimethylphenyl ammonium ethoxide or trimethylphenyl ammonium hydroxide
• a base such as aqueous sodium hydroxide, or alcoholic sodium ethoxide.
• the present invention is directed to a process for the preparation of codeine from morphine which comprises the steps of a) reacting morphine with a methylating agent in the presence of a hydrocarbon solvent at a temperature of approximately 100 to 115°C under reflux conditions such that approximately 50% or more of the hydrocarbon solvent is returned to the reaction mixture to substantially avoid the formation of codeine methyl ether; and b) recovering codeine from the reaction mixture.
• the present invention is also directed to such a process in which step a) above is followed by b) cooling the reaction mixture to approximately 85°C and adding water to terminate the reaction; c) raising the pH of the reaction mixture to approximately 11 ; d) separating the hydrocarbon solvent phase containing codeine and dimethylaniline from the aqueous phase containing unreacted morphine; and e) adding a dilute mineral or organic acid and approximately 6 to 7 times the volume of water for each volume of hydrocarbon solvent to effect a separation of dimethylaniline and codeine.
• the methylation reaction is carried out at a temperature of approximately 90° to 110°.
• Any compatible hydrocarbon solvent such as toluene or xylene may be used as the reaction medium and the methylating agent may be one of those known to those skilled in the art such as trimethylphenyl ammonium chloride, trimethylphenyl ammonium ethoxide, diazomethane or dimethyl sulfate.
• the reaction mixture is cooled to a temperature of approximately 50° to 85°C and water is added to terminate the reaction. Due to the basic nature of the methylating solution, the resulting toluene-water mixture is basic with a pH of approximately 9-10.
• a small portion of sodium hydroxide or other alkaline material is added to render the mixture more strongly basic with a pH of approximately 11-12. At this pH, unreacted morphine is soluble in water and separation of the water and toluene phases effects a separation of unreacted morphine and codeine.
• the toluene phase contains both codeine and dimethylaniline which is left over after the methylating solution of trimethylphenyl ammonium ethoxide has reacted and is neutralized.
• Dimethylaniline is slightly less basic than codeine and remains in the free base form at a pH of 5.0 to 6.0, while codeine is in the salt form in this pH range.
• codeine is water-soluble and as a free base, the dimethylaniline is soluble in toluene in this pH range.
• a dilute mineral or organic acid is added to adjust the pH to approximately 4.0 to 6.0 and approximately six to seven times the volume of water for each volume of hydrocarbon solvent is added to effect a separation of dimethylaniline and codeine in the hydrocarbon solvent phase.
• any dilute mineral or organic acid such as acetic acid, sulfuric acid or hydrochloric acid may be used.
• the morphine starting material may be highly purified or of technical grade and may be in the form of a stable monohydrate containing 5.9% water by weight or even greater levels of water.
• control of codeine methyl ether formation, the removal of unreacted morphine, dimethylaniline and color bodies formed during the methylation reaction advantageously allows for the remaining codeine to be de-colorized via chromatography or other means known to those skilled in the art.
• Example 1 A one-liter flask was charged with 525 ml. of toluene. Either fresh toluene or toluene containing a small portion of codeine from previous use may be employed. 46.5 grams (0.163) gram-moles) of morphine was added to the toluene. The morphine may also contain various amounts of codeine and, in this example, 11.1 grams of codeine (0.037 gram-moles) were part of the morphine charge.
• the resulting toluene-morphine slurry was heated and stirred to a temperature of 111 °C with azeotropic removal of the contained water and under reflux conditions whereby more than 50% of the toluene portion was returned from the azeotrope to the slurry.
• a methylating slurry was prepared as follows: 28.0 grams (0.163 gram- moles) of a commercial grade of trimethylphenyl ammonium chloride was combined with 60.8 mL or 0.163 gram-moles of a 21% commercial solution of sodium ethoxide in ethanol. 95 mL of ethanol was added to complete the mixture. The methylating slurry was added to the dehydrated morphine slurry in toluene at a temperature of 90 to 105°C over the course of one hour. The addition time minimum is 0.5 hours.
• the condenser setup included enough surface area to return more than 50% of the toluene distilled back to the reaction medium while driving off the lower boiling ethanol.
• Ethanol is part of the methylating solution, but is also a by-product of the reaction between morphine and ethoxide anion.
• the addition of the methylating solution may occur over a period of 0.5 to 3 hours. 18 ml. of ethanol was used to rinse the addition apparatus. After addition and rinse, the reaction mixture was heated to 110°C.
• the mixture was then cooled to a temperature of 85°C or less, and 200 ml of water was added as a quenching fluid to terminate the reaction.
• the resulting two phase system had a pH of 9.13.
• Two ml. of a 25% solution of sodium hydroxide in water was added to the toluene phase and the resulting mixture had a pH of 11.7.
• the phases were allowed to settle and then separated.
• the aqueous phase contained any unreacted morphine, approximately 5.5% in this example, and the toluene phase contained codeine and dimethylaniline.
• the toluene phase (375 ml) was mixed with 3 liters of water or an aqueous process stream containing codeine.
• 70 ml of a 3N solution of sulfuric acid was added with stirring to the mixture of toluene and water and the resulting mixture had a pH of 5.7. This pH may range from approximately 4.0 to 6.0, preferably from approximately 5.0 to 5.7.
• the phases were allowed to settle and then separated.
• the aqueous phase containing codeine was separated and measured at 3273 ml.
• the codeine solution is about 15-20 mg/ml and is suitable for decolorization and isolation.
• Example 2 A laboratory reaction vessel is charged with 300 ml. of toluene.
• the toluene used can be fresh or contain a small portion of codeine from previous use.
• 33.7 grams (0.118 gram-moles) of morphine was added to the toluene.
• the morphine used can be highly purified or of technical grade.
• the morphine also contained 6.6 grams (0.022 gram-moles) of codeine.
• the azeotropic removal of water by heating prior to the methylation reaction removed the water of hydration from the morphine under reflux conditions such that there was a return of more than 50% of the toluene to the reaction slurry.
• a methylating slurry was prepared as follows: 20.2 grams (0.118 gram- moles) of a commercial grade of trimethylphenyl ammonium chloride was combined with sodium ethoxide in ethanol. A 21% solution of the commercial grade was used in the amount of 44.0 ml. or 0.118 moles of sodium ethoxide. 68 ml of ethanol was used to complete the mixture.
• the methylating slurry steadily over a period of two hours and ten minutes. This time may vary from an effective minimum of about 0.5 hours to a period with no upper limit.
• the addition of the methylating slurry is done under 100% reflux return in this example.
• a 15 ml rinse of ethanol was done to. insure complete transfer of the methylating slurry.
• the reflux/reaction temperature fell to approximately 84.8°C after the rinse and the reaction mixture was then heated to 110°C under distillation conditons.
• the reaction mixture was then cooled to approximately 86°C and quenched by the addition of 150 ml. of deionized water. About 1 ml.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2002
  • 2002-10-21 US US10/274,702 patent/US6579985B1/en not_active Expired - Lifetime
• 2003
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