WO2005063707A1 - Enantiospecific process for the preparation of paroxetine intermediate - Google Patents

Enantiospecific process for the preparation of paroxetine intermediate Download PDF

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WO2005063707A1
WO2005063707A1 PCT/IN2004/000247 IN2004000247W WO2005063707A1 WO 2005063707 A1 WO2005063707 A1 WO 2005063707A1 IN 2004000247 W IN2004000247 W IN 2004000247W WO 2005063707 A1 WO2005063707 A1 WO 2005063707A1
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acid
formula
compound
toluene
xxi
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French (fr)
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Muddasani Pulla Reddy
Reddy Peddi Rajasekhara
Nannapaneni Venkaiah Chowdary
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Natco Pharma Limited
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D211/00—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings
    • C07D211/04—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D211/06—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members
    • C07D211/36—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D211/60—Carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C215/00—Compounds containing amino and hydroxy groups bound to the same carbon skeleton
    • C07C215/02—Compounds containing amino and hydroxy groups bound to the same carbon skeleton having hydroxy groups and amino groups bound to acyclic carbon atoms of the same carbon skeleton
    • C07C215/22—Compounds containing amino and hydroxy groups bound to the same carbon skeleton having hydroxy groups and amino groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being unsaturated
    • C07C215/28—Compounds containing amino and hydroxy groups bound to the same carbon skeleton having hydroxy groups and amino groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being unsaturated and containing six-membered aromatic rings
    • C07C215/30—Compounds containing amino and hydroxy groups bound to the same carbon skeleton having hydroxy groups and amino groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being unsaturated and containing six-membered aromatic rings containing hydroxy groups and carbon atoms of six-membered aromatic rings bound to the same carbon atom of the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
    • C07C229/02—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton
    • C07C229/04—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated
    • C07C229/06—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton
    • C07C229/10—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton the nitrogen atom of the amino group being further bound to acyclic carbon atoms or to carbon atoms of rings other than six-membered aromatic rings
    • C07C229/12—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton the nitrogen atom of the amino group being further bound to acyclic carbon atoms or to carbon atoms of rings other than six-membered aromatic rings to carbon atoms of acyclic carbon skeletons
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C309/00—Sulfonic acids; Halides, esters, or anhydrides thereof
    • C07C309/63—Esters of sulfonic acids
    • C07C309/64—Esters of sulfonic acids having sulfur atoms of esterified sulfo groups bound to acyclic carbon atoms
    • C07C309/65—Esters of sulfonic acids having sulfur atoms of esterified sulfo groups bound to acyclic carbon atoms of a saturated carbon skeleton
    • C07C309/66—Methanesulfonates
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D211/00—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings
    • C07D211/04—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D211/06—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members
    • C07D211/08—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hydrocarbon or substituted hydrocarbon radicals directly attached to ring carbon atoms
    • C07D211/18—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hydrocarbon or substituted hydrocarbon radicals directly attached to ring carbon atoms with substituted hydrocarbon radicals attached to ring carbon atoms
    • C07D211/20—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hydrocarbon or substituted hydrocarbon radicals directly attached to ring carbon atoms with substituted hydrocarbon radicals attached to ring carbon atoms with hydrocarbon radicals, substituted by singly bound oxygen or sulphur atoms
    • C07D211/22—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hydrocarbon or substituted hydrocarbon radicals directly attached to ring carbon atoms with substituted hydrocarbon radicals attached to ring carbon atoms with hydrocarbon radicals, substituted by singly bound oxygen or sulphur atoms by oxygen atoms
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D405/00—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom
    • C07D405/02—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings
    • C07D405/12—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings linked by a chain containing hetero atoms as chain links
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
    • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
    • C07B2200/07—Optical isomers

Definitions

  • the present mvention relates to an improved process for the preparation of (-)-trans-4-(4- fluorophenyl)-3-hydroxymethyl-l-methylpiperidine.
  • (-)-trans-4-(4-Fluorophenyl)-3- hydroxymethyl-1-methylpiperidine prepared by the process of the invention has the formula-I,
  • (-)- ⁇ II (paroxetine) (-)-trans-4-(4-Fluorophenyl)-3-hydroxymethyl-l-methylpiperidine is a key intermediate used in the synthesis of paroxetine ((-)-trans-4-p-fluorophenyl-3-(3',4'- methylenedioxyphenoxymethyl)-piperidine) of the formula-II.
  • Paroxetine is a serotonine reuptake inhibitor which has been used clinically for the treatment of depression (S. M.
  • (+)-I a number of processes for the preparation of (+)-I were disclosed in various patents. Some of them include US Pat. No. 5,258,517; US Pat. No. 4,902,801; EP No. 374,675; EP No. 802,185; ES Patent No. 96 00,369; EP No. 812827; WO 98 53,824; EP No. 812,827; WO 00/026187 and WO 02/053537. Resolution of this mixture to get (-)-I leads to a loss of more than 50% of unwanted isomer which represents a severe disadvantage of the above processes.
  • the compound of the formula-XXV can be prepared by the generation of an anion ⁇ to the ester carbon present in compound of the formula XXIV and .intramolecular cyclization through displacement of the leaving group OX.
  • the ester group present in compound of the formula-XXV can be reduced with a number of reagents like sodium borohydride or lithium aluminum hydride to get the desired compound of the formula-I in more than 97% chiral purity.
  • compound of the formula-XX can be resolved into its single isomers by treating it with a chiral acid and preferential crystallization of the required salt in a suitable solvent.
  • the acid used in the resolution step is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p- toluoyltartaric acid, (+)-tartaric acid, etc., preferably (+)-Mandelic acid.
  • the solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
  • the solvent used for the recrystallization of the resolved amine salt is same as the solvent used for crystallization or different.
  • the quantity of chiral acid used in the resolution step is at least one molar equivalent to the amine.
  • Chiral amine of the formula-XXI can be isolated from diastereomeric salt by neutralization with inorganic base and extraction of liberated amine with a solvent.
  • the inorganic base used for neutralization of salt is selected from sodium or potassium carbonate, bicarbonate, hydroxide, preferably sodium hydroxide.
  • the solvent used for extraction of liberated amine is selected from hydrocarbon solvents such as toluene, hexane, heptane, cyclohexane, etc, preferably toluene, or cyclohexane. Chiral purity of the amine by chiral HPLC was found to be more than 99.9%.
  • the resolved amine of formula-XXI can be hydrogenated in the presence of heterogeneous metal catalyst to get the secondary amine of formula-XXII.
  • the hydrogenation can be done on free amine of formula-XXI or on its acid addition salt.
  • the acids used for salt formation are selected from organic or mineral acids.
  • the organic acids include, acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc.
  • the mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc.
  • the metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel.
  • the chiral amine of formula-XXII can be reacted with methyl or ethyl acrylate to get the 1, 4-addition product of formula-XXIII.
  • the reaction can be done in a number solvents such as toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., preferably toluene or heptane.
  • the temperature of the reaction is in the range of 20-90°C, preferably 50-60°C.
  • Compound of formula-XXIII can be isolated from the reaction mass by simple distillation of solvent and excess reagent.
  • Hydroxy group present in compound of formula-XXIII can be converted into a facile leaving group such as benzenesulfonate, methanesulfonate, toluenesulfonate, trifluoromethanesulfonate, etc., preferably methanesulfonate or benzenesulfonate.
  • the reaction can be done in various solvents such halogenated solvents (methylene chloride, dichloroethane, chloroform, et.), hydrocarbon solvents (toluene, cyclohexane, hexane, heptane) or ether solvents (diethyl ether, diisopropyl ether, dioxane, THF).
  • the sulfonate derivatives of the formula-XXIV can be reacted with a strong base (NaH, n-butyl lithium, potassium t-butoxide, lithium diisopropyl amide, etc.) in a hydrocarbon/ether and/or dipolar aprotic solvent such as N,N-dimethylformamide, N,N- dimethylacetamide, dimethyl sulfoxide.
  • a strong base NaH, n-butyl lithium, potassium t-butoxide, lithium diisopropyl amide, etc.
  • a hydrocarbon/ether and/or dipolar aprotic solvent such as N,N-dimethylformamide, N,N- dimethylacetamide, dimethyl sulfoxide.
  • the ether solvent used is such as tetrahydrofuran, dioxane, diisopropyl ether
  • the hydrocarbon solvent used is such as toluene, hexane, heptane,
  • the cyclized compound of the formula-XXV can be reduced using sodium borohydride under various conditions (sodium borohydride/borontrifluoride-etherate, sodium , borohydride/t-butanbl/methanol, reflux; t-butanol/acetic acid, ⁇ etc.), vitride, sodium/ethanol, lithium tris-(t-butoxy)aluminum hydride, lithium aluminum hydride, etc., to get the required compound of the formula-I.
  • the medium of the reaction can be an alcoholic solvent (for sodium borohydride), hydrocarbon solvent for vitride, and an ether solvent for lithium reagents.
  • the invention provides novel chiral compound of the formula-XXI, XXI its isomer and the acid addition salts.
  • the invention also provides a process for the preparation of chiral compound of the formula-XXI,
  • chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)- c camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid.
  • the solvent used in step (i) and (ii) i cs selected from alcoholic solvent such as methanol, ethanol, isopropanol, t-butanol, etc., preferably methanol or isopropanol, or a combination of alcoholic solvent with ether solvent such as THF, dioxane, etc., or a hydrocarbon solvent such as toluene, xylene, cyclohexane, heptane, etc.
  • alcoholic solvent such as methanol, ethanol, isopropanol, t-butanol, etc.
  • ether solvent such as THF, dioxane, etc.
  • hydrocarbon solvent such as toluene, xylene, cyclohexane, heptane, etc.
  • the inorganic base used in neutralization step (iii) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, etc.
  • the solvent used for extraction of chiral amine in step (iv) is selected from hydrocarbon solvent such as toluene, xylene, hexane, heptane, cyclohexane, etc.; ester solvent such as ethyl acetate, isopropyl acetate; ether solvent such as diethyl ether, diisopropyl ether, methyl isobutyl ether, methyl t-butyl ether; halogenated solvent such as methylene chloride, ethylene chloride, chloroform.
  • the invention provides novel chiral compound of the formula-XXII,
  • the invention also provides a process for the preparation of chiral compound of the formula-XXII,
  • XXII which comprises: (i) Resolution of the amine compound of formula-XX, XX
  • the invention provides novel compounds of formula-XXIII,
  • the chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)- camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid.
  • the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
  • the organic acids include acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc.
  • the mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc.
  • the metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel.
  • the acid addition salt of the compound of formula-XXII thus obtained can be neutralized with a base and extracted into a
  • the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., preferably toluene or heptane.
  • the temperature of the reaction in step (iii) is in the range of 20-90°C, preferably 50-60°C.
  • Compound of formula-XXIII can be isolated from the reaction mass by simple distillation of solvent and excess reagent.
  • the invention provides novel compounds of formula-XXIV,
  • the invention provides a process for the preparation of compound of formula-XXIV,
  • the invention provides an improved process for the preparation of compound of the formula-I,
  • the chiral acid used in resolution step (i) is selected from ( ⁇ )-Mandelic acid, (+)- 10 camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid.
  • the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
  • the organic acids include acetic acid, propionic acid, oxalic acid, 15 succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc.
  • the mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc.
  • the metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel. The acid addition salt of the compound of formula-XXII thus obtained can be neutralized with a base and extracted
  • the acrylate ester used in step (iii) is selected from methyl or ethyl acrylate and the like.
  • the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., • 25 preferably toluene or heptane.
  • the temperature of the reaction in step (iii) is in the range of 20-90°C, preferably 50-60°C. borohydide/t-butanol/methanol, vitride, lithium aluminum hydride.
  • the temperature of reaction in step (vi) is in the range of -50°C to 70°C, preferably -20°C to 20°C. '
  • the chiral purity of the (-)-trans isomeric compound of formula-XXV obtained from the reaction is in the range of 95-98%. Chiral purity can be raised to more than 99.8% after converting it to the required compound of the formula-I and crystallization of compound of formula-I. Alternatively, chiral purity of compound of formula-XXV can be raised to >99.8% by forming a diastereomeric salt with a chiral acid and neutralization of the diastereomeric salt with a base.
  • (+)-mandelic acid salt Into a 2-L, three-necked RB flask was charged 200 g of ( ⁇ )-N-benzyl-N-methyl-N-[3- hydroxy-3-(4-fluorophenyl)]propyl-amine, 650 mL of isopropanol, and 110 g of (+)- mandelic acid. The reaction mass was heated to 50-55 °C and maintained for 1 hr to get a clear solution.
  • reaction mass was allowed to cool to 25-30 °C and filtered and the wet solid washed with 50 mL of isopropanol to get 140 g of (+)-N-benzyl-N-methyl-N- [3-hydroxy-3-(4-fluorophenyl)]propyl-amine (+)-mandelic acid salt.
  • the above crude mandelate salt was taken into a 2-L, three-necked, RB flask and added 600 mL of isopropanol. After heating to 70 °C a clear solution formed. The resultant solution was allowed to cool to 25-30 °C and maintained for 1 hr.
  • the reaction mass was filtered and the solid washed with 100 mL of isopropanol to get 125 g of pure mandelate
  • the reagents used in step (iv) for the conversion of the hydroxy group to OX is selected from methanesulfonyl chloride, ethanesulfonyl chloride, benzenesulfonyl chloride, p- toluenesulfonyl chloride, acetyl chloride, benzoyl chloride, trifluoromethanesulfonyl chloride, etc., preferably, methanesulfonyl chloride, benzenesulfonyl chloride.
  • the solvent used in step (iv) is selected from methylene chloride, ethylene dichloride, toluene, cylcohexane, heptane, THF, ether, diisopropyl ether etc., preferably, methylene chloride, toluene or heptane and the reaction temperature is in the range of -20 to 25°C, preferably -5 to 15°C.
  • the base used in step (iv) is selected from triethylamine, pyridine, lutidine, sodium or potassium carbonate, or bicarbonate, etc., preferably, pyridine or triethylamine.
  • the strong base used in step (v) is selected from sodium hydride, butyl lithium, hexyl lithium, lithium diisopropylamide, sodium t-butoxide, potassium t-butoxide, sodium sec- amyloxide, sodium amide, lithium amide, sodium methoxide, and the like, preferably sodium hydride or lithium diisopropylamide.
  • the solvent used in step (v) is selected from N,N-dimethylformamide, N,N- dimethylacetamide, pyridine, dimethylsulfoxide, tetrahydrofuran, dioxane, toluene, xylene, diisopropyl ether, etc., preferably N,N-dimethylformamide, dimethylsulfoxide, pyridine, tetrahydrofuran, more preferably N,N-dimethylformamide, tetrahydrofuran.
  • the temperature of reaction in step (v) is between -10 and 45°C, preferably -5 to 25°C.
  • the mole ratio of base to substrate in step (v) is in the range of 1 :1.1 to 1:2.0, preferably 1:1.25.
  • the reducing agent used in step (vi) is selected from sodium borohydride/t- butanol/methanol, sodium borohydride in the presence of an acid catalyst like boron trifluoride-etherate, sulfuric acid, etc.; vitride, lithium aluminum hydride, lithium tris-(t- b ⁇ toxy)aluminum hydride, sodium/ethanol, and the like, preferably, sodium salt.
  • step (i) salt was added to the reaction mass and kept under stirring for 6 hr.
  • the reaction mass was filtered and the cake washed with 100 mL of isopropanol and dried to get 40 g of sodium mandelate.
  • the isopropanol filtrate was taken into a RB flask and distilled off solvent under vaccum. The residue was suspended in water (150 mL) and extracted with toluene (2 x 300 mL).
  • step (iii) (+)-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propyIamine
  • step (ii) compound Into a 1-L stainless steel kettle are charged 50 g of above step (ii) compound, 500 mL of isopropanol, 11 g of acetic acid, and 2.5 g of 5% palladium-on-carbon (50% wet). After evacuating the kettle it was filled with hydrogen and shaken under hydrogen pressure of 40-60psi at room temperature.
  • reaction mass was allowed to cool to 25-30 °C and filtered and the wet solid washed with 100 mL of isopropanol to get 138 g of (-)-N-benzyl-N-methyl-N- [3-hydroxy-3-(4-fluorophenyl)]propyl-amine (-)-mandelic acid salt.
  • step (i) salt was added to the reaction mass and kept under stirring for 6 hr.
  • the reaction mass was filtered and the cake washed with 100 mL of isopropanol and dried to get 40 g of sodium mandelate.
  • the isopropanol filtrate was taken into a RB flask and distilled off solvent under vaccum. The residue was suspended in water (150 mL) and extracted with toluene (2 x 300 mL).
  • step (ii) compound Into a 1-L stainless steel kettle are charged 50 g of above step (ii) compound, 500 mL of isopropanol, 11 g of acetic acid, and 2.5 g of 5% palladium-on-carbon (50% wet). After evacuating the kettle it was filled with hydrogen and shaken under hydrogen pressure of 40-60psi at room temperature. After maintaining under hydrogen pressure for 6 hr reaction mass was filtered and the filtrate distilled under vaccum to get 43 g of crude acetate salt of (-)-N-methyl-N-[3-l ⁇ ydroxy-3-(4-fluorophenyl)]propylamine.

Abstract

A novel, improved, and enantiospecific process for the preparation of (-)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-1-methylpiperidine of formula-(I), an advanced intermediate in the manufacture of antidepressant drug paroxetine is disclosed in the present invention. Compound of formula-(XXII) is prepared by resolution of compound of formula-(XX) using a chiral acid followed by hydrogenation of the resolved amine. Michael addition of the compound of formula-(XXII) onto acrylate esters gave the compounds of formula-(XXIII). Conversion of the hydroxy group present in compound of formula-(XXIII) into a leaving group followed by treatment with a strong base gave the enantiospecific intramolecularly cyclized piperidine derivative of formula-(XXV). Reduction of the ester group present in compound of formula-(XXV) with a metal hydride reducing agent gave the compound of formula-I with more than 97% chiral purity. Further purification of compound of formula-I to >99.5% is achieved by one recrystallization from a number of solvents. Present process is easily adaptable for commercial preparation of (-)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-1-methylpiperidine of formula-(I).

Description

ENANTIOSPECIFIC PROCESS FOR THE PREPARATION OF PAROXETINE INTERMEDIATE
The present mvention relates to an improved process for the preparation of (-)-trans-4-(4- fluorophenyl)-3-hydroxymethyl-l-methylpiperidine. (-)-trans-4-(4-Fluorophenyl)-3- hydroxymethyl-1-methylpiperidine prepared by the process of the invention has the formula-I,
Figure imgf000003_0001
(-)-ι II (paroxetine) (-)-trans-4-(4-Fluorophenyl)-3-hydroxymethyl-l-methylpiperidine is a key intermediate used in the synthesis of paroxetine ((-)-trans-4-p-fluorophenyl-3-(3',4'- methylenedioxyphenoxymethyl)-piperidine) of the formula-II. Paroxetine is a serotonine reuptake inhibitor which has been used clinically for the treatment of depression (S. M.
Hassan, et al, Brit. J. Clin. Pharmacol, 1985, 19, 705; L. E. Dahl et al., Acta Osychiatr.
Scand., 1982, 9, 66). US pat. No. 3,912,743 delineates some of paroxetine's pharmacological properties.
BACKGROUND OF INVENTION
For the first time, the (±)-compound of formula-I was disclosed in the US patent No
3,912,743. Subsequently it was also disclosed in the US patent no 4,007,196. Process disclosed in these patents is based on a Grignard reaction in which arecoline and 4- fluorophenylmagnesium bromide are reacted.
The main disadvantage of this process is that arecoline is very irritant and harmful to the persons involved in the usage and is also not commercially available. The process produces mixture of two stereoisomers in equal ratio. Therefore, it involves a resolution step and the unwanted isomer is of no use. Therefore, this process is not suitable for commercial preparation.
Subsequently, a number of processes for the preparation of (+)-I were disclosed in various patents. Some of them include US Pat. No. 5,258,517; US Pat. No. 4,902,801; EP No. 374,675; EP No. 802,185; ES Patent No. 96 00,369; EP No. 812827; WO 98 53,824; EP No. 812,827; WO 00/026187 and WO 02/053537. Resolution of this mixture to get (-)-I leads to a loss of more than 50% of unwanted isomer which represents a severe disadvantage of the above processes.
Keeping in view of the disadvantages of the process leading to formation of (±)-trans compound of formula-I a number of groups developed enantiospecific processes for the preparation of compound, of the formula-I. Some of the processes that gave more than 70% of the required isomer of formula-I are given below.
In Tetrahedron Letters, 2001, 7805, a process for the preparation compound of the formula-I is disclosed starting from 2-piperidone derivative. Key step in this process is the introduction of 4-fluorophenyl group via 1,4-Michael addition to the compound of formula-VI in a stereospecific manner. Reduction of the compound of formula- VII gave the required compound of the formula-I.
Figure imgf000004_0001
Scheme-I The main disadvantage of the process is that it involves handling of a chiral reagent (R* shown in scheme) which is not commercially available and very expensive. Also, the process produces the required (-)-I isomer in 80%. Purification of this isomer to >99% requires a conventional resolution step which is not commercially attractive over the above mentioned process for the (+)-trans-I.
In the US patent No 6,066,737 a process for the preparation of compound of the formula- I is disclosed starting from pyridine-3-carboxaldehyde (Scheme-II). According to the process pyridine-3-carboxaldehyde is converted to an aminal using a chiral compound 1,2-diarylethylenediamine derivative. 1,4-Reduction of pyridine ring gave the compound of the formula-X as major isomer. Liberation of the protecting group and reduction of the dihydropyridine ring gave the required compound of the formula-I.
Figure imgf000005_0001
XI XII Scheme-II Disadvantages of this, process are that it requires a costly and rarely available chiral amine (N,N'-dimethyl-2,3-diphenylethylenediamine). Also, formation of piperidine ring requires a hydrogenation step which would lead to the formation of a desfluoro impurity in the process. Removal of this impurity from required conψound of formula-I is very difficult.
Stereoselective synthesis of the compound of the formula-I is disclosed in US patent no 5,962,689 using a starting material of formula-XIII where R is chiral auxiliary which controls the stereochemistry during 1,4-Michael addition of organometallic reagents (Scheme-Ill). Ratio of the required isomer formed in this process is only 80%. Remaining 20% of the unwanted isomer was removed by separation techniques such as column chromatography.
Figure imgf000006_0001
Scheme-Ill Main drawback of this process is that the compound of formula-I is produced with 80% purity. Increasing the purity to required level needs a column chromatography which is not commercially viable.
Keeping in view of the difficulties in commercialization of the above mentioned processes we aimed to develop a versatile method that could control the stereochemistry at C-3 and C-4 of compound of the formula-I in more than 95%.
SUMMARY OF INVENTION Recently we developed a novel process (shown in Scheme-IV) for the preparation of (±)- trans compound of formula-I which is the subject matter of our Indian patent application bearing no 830/MAS/2002. According to the process disclosed in the said patent application the compound of the formula-XVI is reacted with an acrylate ester and converted the hydroxy group present in the compound of the formula-XVII to a leaving group and treated with a strong base to get the piperidine derivative of the formula-XIX. Reduction of the ester group present in compound of formula-XIX with a reducing agent gave the compound of formula-I.
Figure imgf000008_0001
XVI
Figure imgf000008_0002
(+/-)-XIX (+/-)-trans-l
Scheme-IV
Piperidine ring formation in the above mentioned process i,s an intramolecular nucleophilic displacement reaction. If the stereochemistry of the leaving group OX in compound of formula-XVIII is fixed, the cyclized product of formula-XIX is also expected to be of stereospecific with opposite stereochemistry. Accordingly, to get the required compound of the formula-I (3S, 4R-isomer), starting compound of the formula- XVI should have the opposite stereochemistry, i. e., S -configuration at the asymmetric center of the compound of formula-XVIII.
Accordingly, process for the preparation of the compound of the formula-I is as given below:
Figure imgf000009_0001
XXIV (-)-XXV (-)-l Scheme-V The amine compound of the formula-XX can be resolved into a chiral amine of the formula-XXI and debenzylated under hydrogenation conditions to get the secondary amine of formula-XXII. The secondary amine of formula-XXII can be reacted with acrylic acid esters to give the corresponding N-alkylated derivative of the formula-XXIII. The hydroxy group present in the compound of the formula-XXIII can be converted to a leaving group OX (X = methanesulfonyl-, toluenesulfonyl-, benzenesulfonyl) to get a compound of the formula-XXI V.
The compound of the formula-XXV can be prepared by the generation of an anion α to the ester carbon present in compound of the formula XXIV and .intramolecular cyclization through displacement of the leaving group OX. The ester group present in compound of the formula-XXV can be reduced with a number of reagents like sodium borohydride or lithium aluminum hydride to get the desired compound of the formula-I in more than 97% chiral purity. DETAILED DESCRIPTION OF INVENTION
In a preferred embodiment of the present invention, compound of the formula-XX can be resolved into its single isomers by treating it with a chiral acid and preferential crystallization of the required salt in a suitable solvent. The acid used in the resolution step is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p- toluoyltartaric acid, (+)-tartaric acid, etc., preferably (+)-Mandelic acid. The solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol. The solvent used for the recrystallization of the resolved amine salt is same as the solvent used for crystallization or different. The quantity of chiral acid used in the resolution step is at least one molar equivalent to the amine.
Chiral amine of the formula-XXI can be isolated from diastereomeric salt by neutralization with inorganic base and extraction of liberated amine with a solvent. The inorganic base used for neutralization of salt is selected from sodium or potassium carbonate, bicarbonate, hydroxide, preferably sodium hydroxide. The solvent used for extraction of liberated amine is selected from hydrocarbon solvents such as toluene, hexane, heptane, cyclohexane, etc, preferably toluene, or cyclohexane. Chiral purity of the amine by chiral HPLC was found to be more than 99.9%.
The resolved amine of formula-XXI can be hydrogenated in the presence of heterogeneous metal catalyst to get the secondary amine of formula-XXII. The hydrogenation can be done on free amine of formula-XXI or on its acid addition salt. The acids used for salt formation are selected from organic or mineral acids. The organic acids include, acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc. The mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc. The metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel. The chiral amine of formula-XXII can be reacted with methyl or ethyl acrylate to get the 1, 4-addition product of formula-XXIII. The reaction can be done in a number solvents such as toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., preferably toluene or heptane. The temperature of the reaction is in the range of 20-90°C, preferably 50-60°C. Compound of formula-XXIII can be isolated from the reaction mass by simple distillation of solvent and excess reagent.
Hydroxy group present in compound of formula-XXIII can be converted into a facile leaving group such as benzenesulfonate, methanesulfonate, toluenesulfonate, trifluoromethanesulfonate, etc., preferably methanesulfonate or benzenesulfonate. The reaction can be done in various solvents such halogenated solvents (methylene chloride, dichloroethane, chloroform, et.), hydrocarbon solvents (toluene, cyclohexane, hexane, heptane) or ether solvents (diethyl ether, diisopropyl ether, dioxane, THF).
The sulfonate derivatives of the formula-XXIV can be reacted with a strong base (NaH, n-butyl lithium, potassium t-butoxide, lithium diisopropyl amide, etc.) in a hydrocarbon/ether and/or dipolar aprotic solvent such as N,N-dimethylformamide, N,N- dimethylacetamide, dimethyl sulfoxide. The ether solvent used is such as tetrahydrofuran, dioxane, diisopropyl ether and the hydrocarbon solvent used is such as toluene, hexane, heptane, cyclohexane, xylene.
The cyclized compound of the formula-XXV can be reduced using sodium borohydride under various conditions (sodium borohydride/borontrifluoride-etherate, sodium , borohydride/t-butanbl/methanol, reflux; t-butanol/acetic acid, ■ etc.), vitride, sodium/ethanol, lithium tris-(t-butoxy)aluminum hydride, lithium aluminum hydride, etc., to get the required compound of the formula-I. The medium of the reaction can be an alcoholic solvent (for sodium borohydride), hydrocarbon solvent for vitride, and an ether solvent for lithium reagents.
The invention provides novel chiral compound of the formula-XXI,
Figure imgf000012_0001
XXI its isomer and the acid addition salts.
Accordingly the invention also provides a process for the preparation of chiral compound of the formula-XXI,
Figure imgf000012_0002
XXI which comprises: (i) Reacting the compound of the formula-XX,
Figure imgf000012_0003
XX with a chiral acid in an organic solvent to get preferentially crystalline (S,S)- diastereomeric salt (ii) Recrystallizing the (S, S)-diastereomeric salt in a solvent to enhance the chiral purity to >99.5% (iii) Neutralizing the (S, S)-diastereomeric salt with an inorganic base (iv) Extracting the liberated chiral amine of the formula-XXI into an organic solvent (v) Removing the solvent by distillation to get the chiral amine of formula-XXI The chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)- c camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid. The solvent used in step (i) and (ii) i cs selected from alcoholic solvent such as methanol, ethanol, isopropanol, t-butanol, etc., preferably methanol or isopropanol, or a combination of alcoholic solvent with ether solvent such as THF, dioxane, etc., or a hydrocarbon solvent such as toluene, xylene, cyclohexane, heptane, etc.
The inorganic base used in neutralization step (iii) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, etc. The solvent used for extraction of chiral amine in step (iv) is selected from hydrocarbon solvent such as toluene, xylene, hexane, heptane, cyclohexane, etc.; ester solvent such as ethyl acetate, isopropyl acetate; ether solvent such as diethyl ether, diisopropyl ether, methyl isobutyl ether, methyl t-butyl ether; halogenated solvent such as methylene chloride, ethylene chloride, chloroform.
The invention provides novel chiral compound of the formula-XXII,
Figure imgf000013_0001
XXII its isomer and acid addition salts.
Accordingly the invention also provides a process for the preparation of chiral compound of the formula-XXII,
Figure imgf000013_0002
XXII which comprises: (i) Resolution of the amine compound of formula-XX,
Figure imgf000014_0001
XX
With a chiral acid to get the resolved amine of formula-XXI,
Figure imgf000014_0002
XXI (ϋ) Hydrogenation of the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of formula-XXII.
The invention provides novel compounds of formula-XXIII,
Figure imgf000014_0003
XXIII wherein R = Me or Et its isomer and acid addition salts.
Accordingly, the invention provides a process for the preparation of compounds of the formula-XXIII,
Figure imgf000015_0001
XXIII wherein R = Me or Et which έomprises: (i) Resolution of the amine compound of formula-XX,
Figure imgf000015_0002
XX With a chiral acid to get the resolved amine of formula-XXI,
Figure imgf000015_0003
XXI (ϋ) Hydrogenation of the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of formula-XXII,
Figure imgf000015_0004
XXII (iii) Reaction of the chiral amine of formula-XXII with methyl or ethyl acrylate in the presence of a solvent at an elevated temperature to get the 1,4-addition product of the formula-XXIII.
The chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)- camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid. The acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids. The organic acids include acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc. The mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc. The metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel. The acid addition salt of the compound of formula-XXII thus obtained can be neutralized with a base and extracted into a suitable organic solvent.
The solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., preferably toluene or heptane. The temperature of the reaction in step (iii) is in the range of 20-90°C, preferably 50-60°C. Compound of formula-XXIII can be isolated from the reaction mass by simple distillation of solvent and excess reagent.
The invention provides novel compounds of formula-XXIV,
Figure imgf000016_0001
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et And its isomers
The invention provides a process for the preparation of compound of formula-XXIV,
Figure imgf000017_0001
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et, Which comprises: (i) Resolution of the amine compound of formula-XX,
Figure imgf000017_0002
XX With a chiral acid to get the resolved amine of formula-XXI,
Figure imgf000017_0003
XXI (ϋ) Hydrogenation of the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of formula-XXII,
Figure imgf000018_0001
XXII (iii) Reaction of the chiral amine of formula-XXII with methyl or ethyl acrylate in the presence of a solvent at an elevated temperature to get the, 1,4-addition product of the formula-XXIII,
Figure imgf000018_0002
XXIII (iv) Conversion of the hydroxy group present in the compound of the formula- XXIII into a leaving group OX with appropriate reagent in a solvent medium with or without a base at low temperature or elevated temperature to get the compound of formula-XXIV
The invention provides an improved process for the preparation of compound of the formula-I,
Figure imgf000018_0003
(-)-I Which comprises: (i) Resolution of the amine compound of formula-XX,
Figure imgf000019_0001
XX With a chiral acid to get the resolved amine of formula-XXI,
Figure imgf000019_0002
XXI (ii) Hydrogenation of the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of formula-XXII,
Figure imgf000019_0003
XXII (iϋ) Reaction of the chiral amine of formula-XXII with methyl or ethyl acrylate in the presence of a solvent at an elevated temperature to get the 1,4-addition product of the formula-XXIII,
Figure imgf000020_0001
XXIII (iv) Conversion of the hydroxy group present in the compound of the formula- XXIII into a leaving group OX with appropriate reagent in a solvent medium with or without a base at low temperature or elevated temperature to get the compound of formula-XXIV,
Figure imgf000020_0002
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et, (v) Reacting the compound of the formula-XXIV with a strong base in the presence in a hydrocarbon/ether and/or dipolar aprotic solvent at a temperature in the range of -20 to 40 °C to get the cyclized compound of formula-XXV,
Figure imgf000021_0001
XXV Wherein R = Me or Et 5 (vi) Reducing the ester group present in the compound of the formula-XXV with a . reducing0 agent to get the compound of the formula-I.
The chiral acid used in resolution step (i) is selected from (÷)-Mandelic acid, (+)- 10 camphorsulfonic acid, (+)-tartaric acid, (+)-di-p-toluoyltartaric acid, etc., preferably (+)- mandelic acid.
The acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids. The organic acids include acetic acid, propionic acid, oxalic acid, 15 succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, etc. The mineral acids used can be such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphate, etc. The metal catalyst used in hydrogenation is selected from 2-10% palladium-on-carbon, Raney nickel. The acid addition salt of the compound of formula-XXII thus obtained can be neutralized with a base and extracted
20 into a suitable organic solvent.
The acrylate ester used in step (iii) is selected from methyl or ethyl acrylate and the like. The solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, etc., • 25 preferably toluene or heptane. The temperature of the reaction in step (iii) is in the range of 20-90°C, preferably 50-60°C. borohydide/t-butanol/methanol, vitride, lithium aluminum hydride. The temperature of reaction in step (vi) is in the range of -50°C to 70°C, preferably -20°C to 20°C. '
The chiral purity of the (-)-trans isomeric compound of formula-XXV obtained from the reaction is in the range of 95-98%. Chiral purity can be raised to more than 99.8% after converting it to the required compound of the formula-I and crystallization of compound of formula-I. Alternatively, chiral purity of compound of formula-XXV can be raised to >99.8% by forming a diastereomeric salt with a chiral acid and neutralization of the diastereomeric salt with a base.
The details of the invention are given in the Examples given below which are provided to illustrate the invention only and therefore should not be construed to limit the scope of the present invention.
Example 1
Preparation of (+)-N-methyI-N-[3-hydroxy-3-(4-fluorophenyl)]propyIamine
(i) Preparation of (+)-N-benzyl-N-methyI-N-[3-hydroxy-3-(4-fluorophenyI)]propyl- amine (+)-mandelic acid salt Into a 2-L, three-necked RB flask was charged 200 g of (±)-N-benzyl-N-methyl-N-[3- hydroxy-3-(4-fluorophenyl)]propyl-amine, 650 mL of isopropanol, and 110 g of (+)- mandelic acid. The reaction mass was heated to 50-55 °C and maintained for 1 hr to get a clear solution. The reaction mass was allowed to cool to 25-30 °C and filtered and the wet solid washed with 50 mL of isopropanol to get 140 g of (+)-N-benzyl-N-methyl-N- [3-hydroxy-3-(4-fluorophenyl)]propyl-amine (+)-mandelic acid salt. Optical rotation is +54.44 (c =l, MeOH).
The above crude mandelate salt was taken into a 2-L, three-necked, RB flask and added 600 mL of isopropanol. After heating to 70 °C a clear solution formed. The resultant solution was allowed to cool to 25-30 °C and maintained for 1 hr. The reaction mass was filtered and the solid washed with 100 mL of isopropanol to get 125 g of pure mandelate The reagents used in step (iv) for the conversion of the hydroxy group to OX is selected from methanesulfonyl chloride, ethanesulfonyl chloride, benzenesulfonyl chloride, p- toluenesulfonyl chloride, acetyl chloride, benzoyl chloride, trifluoromethanesulfonyl chloride, etc., preferably, methanesulfonyl chloride, benzenesulfonyl chloride.
The solvent used in step (iv) is selected from methylene chloride, ethylene dichloride, toluene, cylcohexane, heptane, THF, ether, diisopropyl ether etc., preferably, methylene chloride, toluene or heptane and the reaction temperature is in the range of -20 to 25°C, preferably -5 to 15°C. The base used in step (iv) is selected from triethylamine, pyridine, lutidine, sodium or potassium carbonate, or bicarbonate, etc., preferably, pyridine or triethylamine.
The strong base used in step (v) is selected from sodium hydride, butyl lithium, hexyl lithium, lithium diisopropylamide, sodium t-butoxide, potassium t-butoxide, sodium sec- amyloxide, sodium amide, lithium amide, sodium methoxide, and the like, preferably sodium hydride or lithium diisopropylamide.
The solvent used in step (v) is selected from N,N-dimethylformamide, N,N- dimethylacetamide, pyridine, dimethylsulfoxide, tetrahydrofuran, dioxane, toluene, xylene, diisopropyl ether, etc., preferably N,N-dimethylformamide, dimethylsulfoxide, pyridine, tetrahydrofuran, more preferably N,N-dimethylformamide, tetrahydrofuran. The temperature of reaction in step (v) is between -10 and 45°C, preferably -5 to 25°C. The mole ratio of base to substrate in step (v) is in the range of 1 :1.1 to 1:2.0, preferably 1:1.25.
The reducing agent used in step (vi) is selected from sodium borohydride/t- butanol/methanol, sodium borohydride in the presence of an acid catalyst like boron trifluoride-etherate, sulfuric acid, etc.; vitride, lithium aluminum hydride, lithium tris-(t- bύtoxy)aluminum hydride, sodium/ethanol, and the like, preferably, sodium salt. Optical rotation is +62,7 (c = 1, MeOH). Melting point is 110-11 ϊ °C. Chiral purity by HPLC is 100%.
(ii) Preparation of (+)-N-benzyI-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propyI- amine
Into a 1-L, three-necked, RB flask were charged 450 mL of isopropanol and 11.5 g of sodium hydroxide. After stirring the reaction mass for 20 min, 125 g of step (i) salt was added to the reaction mass and kept under stirring for 6 hr. The reaction mass was filtered and the cake washed with 100 mL of isopropanol and dried to get 40 g of sodium mandelate. The isopropanol filtrate was taken into a RB flask and distilled off solvent under vaccum. The residue was suspended in water (150 mL) and extracted with toluene (2 x 300 mL). The toluene layer was washed with water, dried and evaporated under vaccum to get 82 g of (+)-N-benzyl-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propyl- amine as liquid. Optical rotation is +22.36 (c = 1, MeOH).
(iii) (+)-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propyIamine Into a 1-L stainless steel kettle are charged 50 g of above step (ii) compound, 500 mL of isopropanol, 11 g of acetic acid, and 2.5 g of 5% palladium-on-carbon (50% wet). After evacuating the kettle it was filled with hydrogen and shaken under hydrogen pressure of 40-60psi at room temperature. After maintaining under hydrogen pressure for 6 hr reaction mass was filtered and the filtrate distilled under vaccum to get 43 g of crude acetate salt of (+)-N-methyl-N-[3-hydiOxy-3-(4-fluorophenyl)]propylamine. The crude salt was suspended in toluene (40 mL) and filtered to get 40 g of pure white crystalline acetate salt. Melting point is 127 °C. Optical rotation is +41.4 (c = 1, MeOH). Purity by HPLC is 99.3% and the des-fluoro impurity is 0.07%.
The above acetate salt was taken into a 1-L, three-necked RB flask and added a solution of aqueous sodium hydroxide (8 g of sodium hydroxide dissolved in 120 mL of water). After stirring for 30 min toluene (100 mL) was added to the reaction mass. Toluene layer was separated and the aqueous layer extracted with 50 mL of toluene. Combined toluene layer was washed with water, dried and distilled off solvent under vaccum to get 30 g liquid (+)-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propylamine. Optical rotation is +32.3 (c = 1, MeOH). HPLC purity is 99.9%.
Example 2
Preparation of (-)-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propylamine
(i) Preparation of (-)-N-benzyI-N-methyl-N-[3-hydroxy-3-(4-fluorophenyI)]propyl- amine (-)-mandelic acid salt
Into a 2-L, three-necked RB flask was charged 200 g of (±)-N-benzyl-N-methyl-N-[3- hydroxy-3-(4-fluorophenyl)]propyl-amine, 650 mL of isopropanol, and 110 g of (-)- mandelic acid. The reaction mass was heated to 50-55 °C and maintained for 1 hr to get a clear solution. The reaction mass was allowed to cool to 25-30 °C and filtered and the wet solid washed with 100 mL of isopropanol to get 138 g of (-)-N-benzyl-N-methyl-N- [3-hydroxy-3-(4-fluorophenyl)]propyl-amine (-)-mandelic acid salt. Optical rotation is - 55.40 (c =l, MeOH).
The above crude mandelate salt was taken into a 2-L, three-necked, RB flask and added 600 mL of isopropanol. After heating to 70 °C a clear solution formed. The resultant solution was allowed to cool to 25-30 °C and maintained for 1 hr. The reaction mass was filtered and the solid washed with 100 mL of isopropanol to get 120 g of pure mandelate salt. Optical rotation is -62.1 (c = 1, MeOH). Melting point is 110-111 °C. Chiral purity by HPLC is 99.5%.
(ii) Preparation of (-)-N~benzyI-N-methyI-N-[3-hydroxy-3-(4-fluorophenyI)]propyl- amine
Into a 1-L, three-necked, RB flask were charged 450 mL of isopropanol and 11 g of sodium hydroxide. After stirring the reaction mass for 20 min, 120 g of step (i) salt was added to the reaction mass and kept under stirring for 6 hr. The reaction mass was filtered and the cake washed with 100 mL of isopropanol and dried to get 40 g of sodium mandelate. The isopropanol filtrate was taken into a RB flask and distilled off solvent under vaccum. The residue was suspended in water (150 mL) and extracted with toluene (2 x 300 mL). The toluene layer was washed with water, dried and evaporated under vaccum to get 80 g of (-)-N-benzyl-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propyl- amine as liquid. Optical rotation is -22.1 (c = 1, MeOH).
(iii) (-)-N-methyI-N-[3-hydroxy-3-(4-fluorophenyl)]propyIamine
Into a 1-L stainless steel kettle are charged 50 g of above step (ii) compound, 500 mL of isopropanol, 11 g of acetic acid, and 2.5 g of 5% palladium-on-carbon (50% wet). After evacuating the kettle it was filled with hydrogen and shaken under hydrogen pressure of 40-60psi at room temperature. After maintaining under hydrogen pressure for 6 hr reaction mass was filtered and the filtrate distilled under vaccum to get 43 g of crude acetate salt of (-)-N-methyl-N-[3-lιydroxy-3-(4-fluorophenyl)]propylamine. The crude salt was suspended in toluene (40 mL) and filtered to get 40 g of pure white crystalline acetate salt. Melting point is 127 °C. Optical rotation is -41.4 (c = 1, MeOH). Purity by HPLC is 99.4% and the des-fluoro impurity is 0.06%.
The above acetate salt was taken into a 1-L, three-necked RB flask and added a solution of aqueous sodium hydroxide (8 g of sodium hydroxide dissolved in 120 mL of water). After stirring for 30 min toluene (100 mL) was added to the reaction mass. Toluene layer was separated and the aqueous layer extracted with 50 mL of toluene. Combined toluene layer was washed with water, dried and distilled off solvent under vaccum to get 30 g of (-)-N-methyl-N-[3-hydroxy-3-(4-fluorophenyl)]propylamineas colorless liquid. Optical rotation is -32.0 (c = l, MeOH). HPLC purity is 99.8%.
Example 3
Preparation of (3S, 4R)-trans-4-(4-fluorophenyI)-3-hydroxymethyl-l-methyI- piperidine of the formula-I (i) Preparation of methyl (+)-3-[N-methyI-N-(3-hydroxy-3-(4-fluorophenyl)propyl)]- aminopropioaate
Into a 1-L, three-necked, RB flask was charged 100 g of (+)-N-methyl-N-[3-hydroxy-3- (4-fluorophenyl)]propylamine and 300 mL of toluene. Methyl acrylate (48 g) was added to the reaction mixture. The reaction mixture was slowly heated to 60-65 °C and maintained for 7 hr. The reaction mixture was cooled to 40 °C and toluene distilled off under vaccum. The residue was dissolved in hexane (150 mL), cooled to 0- 5 °C, and filtered to give 140 g of white solid. Melting point is 43.3 °C. Optical rotation is +23.5 (c = 1, MeOH).
(ii) Preparation of methyl (+)-3-[N-methyI-N-(3-methanesulfonyloxy-3-(4-fluoro- phenyl)propyl)]aminopropionate
Into a 2-L, three-necked, RB flask was charged 850 mL of methylene chloride and 100 g of methyl (+)-3-[N-methyl-N-(3-hydroxy-3-(4-fluorophenyl)propyl)]aminopropionate under nitrogen atmosphere. The reaction mixture was cooled to -5 to 0 °C and triethylamine (51 g) was added. A solution of methanesulfonyl chloride (51 g) in methylene chloride (100 mL) was added to the reaction mixture slowly over a period of 4-5 hr and kept under maintenance for additional 10 hr. The reaction mixture was poured into 450 mL of chilled water and extracted the product into methylene chloride. Aqueous layer was extracted with 2 x 150 mL of methylene chloride. Combined methylene chloride layer was washed with water and dried over sodium sulfate. Distillation of methylene chloride gave the crude compound (89 g) as syrup. This was found to be sufficiently pure enough for further conversion. Optical rotation is +60.0 (c = 1, MeOH).
(iii) Preparation of (3S, 4R)-trans-3-carbomethoxy-4-(4-fluorophenyl)-N-methyI- piperidine
Into a 1-L, three-necked, RB flask were charged 400 mL of dry DMF and 89 g of compound obtained in step (ii) above under nitrogen atmosphere. The reaction mixture was cooled to -15 to -10 °C and added sodium hydride (14.5 g, 55%) in lots over a period of 1 hr. The reaction mixture was maintained at same temperature for 3 hr and slowly allowed to reach 25-30 °C over a period of 5-6 hr. The reaction mixture was maintained at 25-30 °C for 12-13 hr and found to be over by TLC. The reaction mixture was cooled to 5-10 °C and quenched with methanol (20 mL). The reaction mixture was poured into 2.3L of chilled water. Toluene (600 mL) was added to the reaction mixture and stirred for 1 hr. Toluene layer was separated and the aqueous layer extracted with toluene (2 x 100 mL). The combined organic layer was washed with water and product extracted into 10% aqueous acetic acid (1 x 400 mL, 2 x 150 mL). Combined acetic acid layer was extracted with 100 mL of toluene. Aqueous acetic acid layer was treated with carbon and neutralized with sodium bicarbonate. The product thus obtained was extracted into toluene (1 x 400 mL, 2 x 150 mL). Toluene was distilled off from the organic layer to leave 47 g of crude compound as syrup. Optical rotation is -45.0 (c = 1, MeOH).
(iv) Preparation of (3S, 4R)-trans-4-(4-fluoropheriyl)-3-hydroxymethyl-l-methyl- piperidine
Into a 1-L, three-necked, RB flask was charged 47 g of the crude compound obtained in step (iii) above and t-butanol (300 mL). Sodium borohydride (10 g) was added to the reaction mixture and heated to reflux temperature. Methanol (50 mL) was added in lots to the reaction mixture over a period of 6 hr. After the last lot addition reaction mixture was maintained at reflux for 2 hr and checked the TLC. Reaction mixture was quenched with
5 mL of acetic acid. Solvent was removed from the reaction mixture under vaccum and water (200 mL) added to the reaction mass. pH of the reaction mass was adjusted to 8-9 with sodium bicarbonate Compound was extracted into toluene (2 x 100 mL). Toluene layer was dried and distilled under vaccum to get 37 g of the crude product. Optical rotation is -35.4 (c = 1, MeOH). Chiral purity by HPLC is 97.5%. The crude compound was crystallized from hexane/toluene to get the pure compound of the formula-I as off- white solid (30 g). Purity by HPLC is 98.5%. Melting point is 98-99 °C.
Example 4
Preparation of (3S, 4R)-trans-4-(4-fluorophenyI)-3-hydroxymethyI-l-methyI- piperidine of formula-I (i) Preparation of (3S, 4R)-trans-3-carbomethoxy-4-(4-fluorophenyl)-N-methyl- piperidine (-)-mandelic acid salt
Into a Ϊ-L, three-necked, RB flask was charged 100 g of crude (3S, 4R)-trans-3- carbomethoxy-4-(4-fluorophenyl)-N-methyl-piperidine obtained according to the procedure given in Example 3 step (iii), 450 mL of isopropanol, and 60 g of (-)-mandelic acid. The reaction mass was heated to 55-60 °C to get a clear solution. The reaction mass was slowly cooled to 25-30 °C and kept under stirring for 12-15 hr. The reaction mass was further cooled- to 5-10 °C and filtered the mass. The wet cake thus obtained was washed with 50 mL of isopropanol and dried to get 135 g of white solid. Melting point is 120 °C. Optical rotation is -69.4 (c = 1, MeOH).
(ii) Preparation of (3S, 4R)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-l-methyl- piperidine
Into a 2-L, three-necked RB flask were charged 500 mL of water, 200 mL of toluene, and 135 g of the compound obtained in step (i) above. Sodium bicarbonate (38 g) was slowly added to the reaction mass under stirring. Layers were separated and the aqueous layer extracted with 2 x 100 mL of toluene. Combined toluene layer was washed with water, dried and evaporated under vaccum to get 83 g of pure (3S, 4R)-trans-3-carbomethoxy-4- (4-fluorophenyl)-N-methyl-piperidine. Optical rotation is -49.5 (c = 1, MeOH).
Into a 1-L, three-necked RB flask was charged 300 mL of anhydrous THF under nitrogen atmosphere. Lithium aluminum hydride (7.5 g) was added to THF and cooled to -30 °C. A solution of 50 g of above pure (3S, 4R)-trans-3-carbomethoxy-4-(4-fluorophenyl)-N- methyl-piperidine in 100 mL of anhydrous THF was slowly added to the reaction mass over a period of 1 hr keeping the temperature below -25°C. After stirring for 30 min reaction was found to be over by TLC. The reaction was quenched by adding 15 mL of water and stirred for lhr at 25-30 °C. The inorganic solids were removed by filtration and washed the salts with 200 mL of ethyl acetate. Solvents were distilled off from the filtrate and the residue dissolved in 200 mL of toluene and washed with 100 mL of water. Toluene was distilled off under vaccum to get 41 g of residue which was crystallized using hexane/toluene (9:1) to get 37 g of pure (3S, 4R)-trans-4-(4-fluorophenyl)-3- hydroxymethyl-1-methyl-piperidine as white solid. Melting point is 99.5 °C. Optical rotation is -38.1 (c = 1, MeOH). Chiral purity by HPLC is 100%. Chemical purity by HPLC is 99.7%.
Example 5
Preparation of (3S, 4R)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-l-methyl- piperidine of formula-I
(i) Preparation of ethyl (+)-3-[N-methyI-N-(3-hydroxy-3-(4-fluorophenyl)propyl)]- aminopropionate
Into a 1-L, three-necked, RB flask was charged 63 g of (+)-N-methyl-N-[3-hydroxy-3-(4- fluorophenyl)]propylamine and 200 mL of toluene. Ethyl acrylate (35 g) was added to the reaction mixture. The reaction mixture was slowly heated to 60-65 °C and maintained for 7 hr. The reaction mixture was cooled to 40 °C and toluene distilled off under vaccum to leave the title compound (93 g) as syrup. Optical rotation is +19.4 (c = 1, MeOH).
(ii) Preparation of ethyl (+)-3-[N-methyI-N-(3-methanesulfonyIoxy-3-(4-fluoro- phenyl)propyl)]aminopropionate
Into a 2-L, three-necked, RB flask was charged 700 mL of methylene chloride and 81 g of ethyl (+)-3-[N-methyl-N-(3-hydroxy-3-(4-fluorophenyl)propyl)]aminopropionate under nitrogen atmosphere. The reaction mixture was cooled to -5 to 0 °C and triethylamine (38.2 g) was added. A solution of methanesulfonyl chloride (38 g) in methylene chloride (100 mL) was added to the reaction mixture slowly over a period of
4-5 hr and kept under maintenance for additional 10 hr. The reaction mixture was poured into 400 mL of chilled water and extracted the product into methylene chloride. Aqueous layer was extracted with 2 x 150 mL of methylene chloride. Combined methylene chloride layer was washed with water and dried over sodium sulfate. Distillation of methylene chloride gave the crude compound (70 g) as syrup. This was found to be sufficiently pure enough for further conversion. Optical rotation is +54.3 (c = 1, MeOH). (iii) Preparation of (3S, 4R)-trans-3-carboethoxy-4-(4-fluorophenyl)-N- methylpiperidine
Into a 1-L, three-necked, RB flask were charged 350 mL of dry DMF and 63 g of compound obtained in step (ii) above under nitrogen atmosphere. The reaction mixture was cooled to -15 to -10 °C and added sodium hydride (11 g, 55%) in lots over a period of 1 hr. The reaction mixture was maintained at same temperature for 3 hr and slowly' allowed to reach 25-30 °C over a period of 5-6 hr. The reaction mixture was maintained at 25-30 °C for 12-13 hr and found to be over by TLC. The reaction mixture was cooled to 5-10 °C and quenched with ethanol (20 mL). The reaction mixture was poured into 700 mL of chilled water. Toluene (500 mL) was added to the reaction mixture and stirred for 1 hr. Toluene layer was separated and the aqueous layer extracted with toluene (2 x 100 mL). The combined organic layer was washed with water and product extracted into 5% aqueous acetic acid r(l x 300 mL,»2 x 100 mL). Combined acetic acid layer was extracted with 100 mL of toluene. Aqueous acetic acid layer was treated with carbon and neutralized with sodium bicarbonate. The product thus obtained was extracted into toluene (1 x 500 mL, 2 x 100 mL). Toluene was distilled off from the organic layer to leave 32 g of crude compound as syrup. Optical rotation is -45.3 (c = 1, MeOH).
Into a 500-mL, three-necked, RB flask were charged 30 g of above crude compound, 150 mL of isopropanol, and 18 g of (-)-mandelic acid. The reaction mixture was heated 55-60 °C and maintained for 1 hr. The resultant solution was slowly allowed to cool to 25-30 °C and maintained for 15 hr. The reaction mixture was cooled to 5-10 °C and filtered the salt. Washed the salt with 50 mL of isoporpanol and dried at 40-50 °C to get 43 g of white solid. Melting point is 117-1 18 °C. Optical rotation is -65.3 (c = 1, MeOH).
Into a 1-L, three-necked RB flask were charged 40 g of above salt, 250 mL of water and 250 mL of toluene. Sodium bicarbonate (15 g) was added to the reaction mixture., Toluene layer was separated and the aqueous layer extracted with 2 x 100 mL of toluene. Combined toluene layer was dried, and evaporated to get 26 g of pure compound as syrup. Optical rotation is -47.1 (c = 1, MeOH). (iv) Preparation of (3S, 4R)-trans-4-(4-fluorophcnyl)-3-hydroxymethyl-l-methyl- piperidinc
Into a 1-L, three-necked, RB flask were charged 10 g of the above step (iii) compound and 70 mL of t-butanol. Sodium borohydride (2 g) was added to the reaction mixture and heated to reflux temperature. Methanol (20 mL) was added in lots to the reaction mixture over a period of 6 hr. After the last lot addition reaction mixture was maintained at reflux for 2 hr and checked the TLC. Reaction mixture was quenched with 2 mL of acetic acid. Solvent was removed from the reaction mixture under vaccum and added water (100 mL) to the residue. pH of the reaction mass was adjusted to 8-9 with sodium bicarbonate and the product extracted into toluene (2 x 75 mL). Toluene layer was dried and distilled under vaccum to get 7 g of the crude product. Optical rotation is -37.8 (c = 1, MeOH). Chiral purity by HPLC is 99.5%.
Example 6 Preparation of (3R, 4S)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-l-methyl- piperidine
(i) Preparation of methyl (-)-3-[N-methyI-N-(3-hydroxy-3-(4-fluorophenyI)propyl)]- aminopropionate Into a 1-L, three-necked, RB flask were charged 100 g of (-)-N-methyl-N-[3-hydroxy-3- (4-fluorophenyl)]propylamine obtained as per the procedure given in Example 2 and 300 mL of toluene. Methyl acrylate (48 g) was added to the reaction mixture. The reaction mixture was slowly heated to 60-65 °C and maintained for 7 hr. Toluene was distilled off from the reaction mixture under vaccum. The residue was dissolved in hexane (150 mL), cooled to 0-5 °C, and filtered to give 138 g of white solid. Melting point is 43 °C. Optical rotation is -23.3 (c = 1, MeOH).
(ii) Preparation of methyl (-)-3-[N-methyl-N-(3-methanesuIfonyIoxy-3-(4-fluoro- phenyl)propyl)]aminopropionate of the formula-XXII Into a 2-L, three-necked, RB flask was charged 850 mL of methylene chloride and 100 g of methyl (-)-3-[N-methyl-N-(3-hydroxy-3-(4-fluorophenyl)propyl)]aminopropionate under nitrogen atmosphere. The reaction mixture was cooled to -5 to 0 °C and triethylamine (51 g) was added. A solution of methanesulfonyl chloride (51 g) in methylene chloride (100 mL) was added to the reaction mixture slowly over a period of 4-5 hr and kept under maintenance for additional 10 hr. The reaction mixture was poured into 450 mL of chilled water and extracted the product into methylene chloride. Aqueous layer was extracted with 2 x 150 mL of methylene chloride. Combined methylene chloride layer was washed with water and dried over sodium sulfate. Distillation of methylene chloride gave the crude compound (86 g) as syrup. This was found to be sufficiently pure enough for further conversion. Optical rotation is -59.5 (c = 1, MeOH).
(iii) Preparation of (3R, 4S)-trans-3-carbomethoxy-4-(4-fluorophenyl)-N-methyl- piperidine
Into a 1-L, three-necked, RB flask were charged 400 mL of dry DMF and 85 g of compound obtained in step (ii) above under nitrogen atmosphere. The reaction mixture was cooled to -15 to -10 °C and added sodium hydride (14.5 g, 55%) in lots over a period of 1 hr. The reaction mixture was maintained at same temperature for 3 hr and slowly allowed to reach 25-30 °C over a period of 5-6 hr. The reaction mixture was maintained at 25-30 °C for 12-13 hr and found to be over by TLC. The reaction mixture was cooled to 5-10 °C and quenched with methanol (20 mL). The reaction mixture was poured into 2.3L of chilled water. Toluene (600 mL) was added to the reaction mixture and stirred for 1 hr. Toluene layer was separated and the aqueous layer extracted with toluene (2 x 100 mL). The combined organic layer was washed with water and product extracted into 10% aqueous acetic acid (1 x 400 mL, 2 x 150 mL). Combined acetic acid layer was extracted with 100 mL of toluene. Aqueous acetic acid layer was treated with carbon and neutralized with sodium bicarbonate. The product thus obtained was extracted into toluene (1 x 400 mL, 2 x 150 mL). Toluene was distilled off from the organic layer to leave 45 g of crude compound as syrup. Optical rotation is +44.7 (c = 1, MeOH).
Into a 500-mL, three-necked, RB flask were charged 45 g of above crude compound, 200 mL of isopropanol, and 27 g of (+)-mandelic acid. The reaction mixture was heated 55-60 °C and maintained for 1 hr. The resultant solution was slowly allowed to cool to 25-30 °C and maintained for 15 hr. The reaction mixture was cooled to 5-10 °C and filtered the salt. Washed the salt with 50 mL of isoporpanol and dried at 40-50 °C to get 62 g of white solid. Melting point is 116-118 °C. Optical rotation is +69.0 (c = 1, MeOH).
Into a 1-L, three-necked RB flask were charged 60 g of above salt, 400 mL of water and 300 mL of toluene. Sodium bicarbonate (25 g) was added to the reaction mixture. Toluene layer was separated and the aqueous layer extracted with 2 x 100 mL of toluene. Combined toluene layer was dried, and evaporated to get 36 g of pure compound as syrup. Optical rotation is +49.2 (c = 1, MeOH).
(iv) Preparation of (3R, 4S)-trans-4-(4-fluorophenyl)-3-hydroxymethyl-l-methyl- piperidine
Into a 1-L, three-necked RB flask was charged 200 mL of anhydrous THF under nitrogen atmosphere. Lithium aluminum hydride (4.5 g) was added to THF and cooled to -30 °C.
A solution of 30 g of above pure (3R, 4S)-trans-3-carbomethoxy-4-(4-fluorophenyl)-N- methyl-piperidine in 100 mL of anhydrous THF was slowly added to the reaction mass over a period of 1 hr keeping the temperature below -25°C. After stirring for 30 min reaction was found to be over by TLC. The reaction was quenched by adding 15 mL of water and stirred for lhr at 25-30 °C. The inorganic solids were removed by filtration and washed the salts with 100 mL of ethyl acetate. Solvents were distilled off from the filtrate and the residue dissolved in 100 mL of toluene and washed with 100 mL of water.
Toluene was distilled off under vaccum to get 24 g of residue which was crystallized using hexane/toluene (9:1) to get 21 g of pure (3R, 4S)-trans-4-(4-fluorophenyl)-3- hydroxymethyl-1 -methyl-piperidine as white solid. Melting point is 97.5 °C. Optical rotation is +38.0 (c = 1, MeOH). Advantages of the Invention (i) The compound of formula-I is formed with >95% enantiospecificity. . (ii) No resolution of compound of formula-I is required hence no wastage, (iii) No costly chiral reagents are used in building the compound of formula-I in a stereospecific manner. (iv) Process is economically viable and commercially feasible. (v) The raw materials employed are cheap and readily available.

Claims

We Claim:
1. An improved process for the preparation of compound of the formula-I,
Figure imgf000035_0001
(-)-ι which is useful for the preparation of paroxetine of formula- ϊi,
Figure imgf000035_0002
II
Which comprises: (i) Resolution of the compound of the formula-XX,
Figure imgf000035_0003
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric salt with a base,
Figure imgf000036_0001
XXI
(ii) Hydrogenating the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of the formula-XXII,
Figure imgf000036_0002
XXII
(iii) Reacting the amine of the formula-XXII with methyl or ethyl acrylate in the presence of a solvent at a temperature in the range of 20-120°C to get the 1,4- addition product of the formula-XXIII,
Figure imgf000036_0003
XXIII
(iv) Converting the hydroxy group present in the compound of the formula-XXIII into a leaving group OX with an appropriate reagent in a solvent medium with or without a base at a temperature in the range of -20 to 60 °C to get the compound of formula-XXIV,
Figure imgf000037_0001
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et, (v) Reacting the compound of the formula-XXIV with a strong base in the presence of a hydrocarbon/ether and / or dipolar aprotic solvent at a temperature in the range of -20 to 40 °C to get the cyclized compound of formula-XXV,
Figure imgf000037_0002
XXV
Wherein R = Me or Et (vi) Reducing the ester group present in the compound of the formula-XXV with a metal hydride reducing agent to get the hydroxy compound of the formula-I.
2. A process as claimed in claim 1 wherein the chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid . (+)-di-p-toluoyltartaric acid or (+)-tartaric acid, preferably, (+)-Mandelic acid.
3. A process as claimed in claims 1 and 2 wherein the: protic solvent used in the crystallization step (i) is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
4. A process as claimed in claims 1 to 3 wherein the base used in neutralization of diastereomeric salt in step (i) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, preferably sodium or potassium hydroxide.
5. A process as claimed in claims 1 to 4 wherein the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
6. A process as claimed in claims 1 and 5 wherein the organic acid used in hydrogenation step (ii) are selected from acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, preferably acetic acid, oxalic acid or mandelic acid.
7. A process as claimed in claims 1 and 5 wherein the mineral acid used in hydrogenation step (ii) is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid.
8. A process as claimed in claims 1 to 7 wherein the metal catalyst used in hydrogenation step (ii) is selected from 2-10% palladium-on-carbon, Raney nickel, preferably 5% Pd- on-carbon.
9. A process as claimed in claims 1 to 8 wherein the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylenp chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, preferably toluene or heptane.
10. A process as claimed in claims 1 to 9 wherein the reagent used in step (iv) for the conversion of the hydroxy group to OX is selected from methanesulfonyl chloride, benzenesulfonyl chloride, p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, preferably, methanesulfonyl chloride or benzenesulfonyl chloride.
11. A process as claimed in claims 1 to 10 wherein the solvent used in step (iv) is selected from methylene chloride, ethylene dichloride, toluene, cylcohexane, heptane,
THF, ether, diisopropyl ether etc., preferably, methylene chloride, toluene or heptane
12. A process as claimed in claims 1 to 11 wherein the base used in step (iv) is selected from triethylamine, pyridine, lutidine, sodium or potassium carbonate, or bicarbonate, etc., preferably, pyridine or triethylamine.
13. A process as claimed in claims 1 to 12 wherein the preferred reaction temperature in step (iv) is in the range of -20 to 25°C, more preferably -5 to 15 °C.
14. A process as claimed in claims 1 to 13 wherein the strong base used in step (v) is selected from sodium hydride, potassium t-butoxide, n-butyl lithium, lithium diisopropyl amide, preferably sodium hydride.
15. A process as claimed in claims 1 to 14 wherein the hydrocarbon solvent used in step (v) is selected from toluene, hexane, hepate, cyclohexane, preferably toluene or cyclohexane.
16. A process as claimed in claims 1 to 15 wherein the ether solvent used in step (v) is selected from diethyl ether, dioxane, THF, methyl t-butyl ether, preferably THF.
17. A process as claimed in claims 1 to 16 wherein the aprotic solvent used in step (v) is selected from dimethylformamide, dimethylacetamide, preferably dimethylformamide.
18. A process as claimed in claims 1 to 17 wherein the preferred temperature of reaction in step (v) is -5 to 25 °C.
19. A process as claimed in claims 1 to 18 wherein the metal hydride reducing agent used in reduction step (vi) is selected from sodium borohydride or its derivatives such as sodium triacetoxy borohydride, lithium aluminum hydride or its derivatives such lithium tri-butoxyaluminum hydride, vitride, preferably sodium borohydride or lithium aluminum hydride.
20. A novel compound of formula-XXI,
Figure imgf000040_0001
XXI its isomer and acid addition salts thereof
21. A process for the preparation of compound of the formula XXI which comprises resolving the compound of the formula-XX,
Figure imgf000040_0002
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric salt with a base.
22. A process as claimed in claim 21 wherein the chiral acid used in resolution is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p-toluoyltartaric acid or (+)- tartaric acid, preferably, (+)-Mandelic acid.
23. A process as claimed in claims 21 & 22 wherein the protic solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
24. A process as claimed in claims 21 to 23 wherein the base used in neutralization of diastereomeric salt is selected from sodium or potassium hydroxide, carbonate, bicarbonate,, preferably sodium or potassium hydroxide.
25. A novel compound of formula-XXII,
Figure imgf000041_0001
XXII its isomer and acid addition salts.
26. A process for the preparation of compound of the formula XXII which comprises: (i) Resolving the compound of the formula-XX,
Figure imgf000041_0002
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric 'salt with a base,
Figure imgf000041_0003
XXI (ii) Hydrogenating* the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of • the formula-XXII,
Figure imgf000042_0001
XXII
27. A process as claimed in claim 26 wherein the chiral acid used in resolution is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p-toluoyltartaric acid or (+)- tartaric acid, preferably, (+)-Mandelic acid.
28. A process as claimed in claims 26 & 27 wherein the protic solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
29. A process as claimed in claims 26 to 28 wherein the base used in neutralization of diastereomeric salt in step (i) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, preferably sodium or potassium hydroxide.
30. A process as claimed in claims 26 to 29 wherein the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
31. A process as claimed in claims 26 to 30 wherein the organic acid used in hydrogenation step (ii) are selected from acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, preferably acetic acid, oxalic acid or mandelic acid.
32. A process as claimed in claims 26 to 31 wherein the mineral acid used in hydrogenation step (ii) is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid.
33. A process as claimed in claims 26 to 32 wherein the metal catalyst used in hydrogenation step (ii) is selected from 2-10% palladium-on-carbon, Raney nickel, preferably 5% palladium-on-carbon.
34. Novel compounds of formula-XXIII,
Figure imgf000043_0001
XXIII
Wherein R = Me or Et isomer and acid addition salts thereof.
35. A process for the preparation of compound of the formula XXIII which comprises-: (i) Resolving the compound of the formula-XX,
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric salt with a base,
Figure imgf000044_0001
XXI
(ii) Hydrogenating the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of the formula-XXII,
Figure imgf000044_0002
XXII (iϋ) Reacting the amine of the formula-XXII with methyl or ethyl acrylate in the presence of a solvent at a temperature in the range of 20-120°C to get the 1,4- addition product of the formula-XXIII,
Figure imgf000044_0003
XXIII
36. A process as claimed in claim 35 wherein the chiral acid used in resolution step (i) is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p-toluoyltartaric acid or (+)-tartaric acid, preferably, (+)-Mandelic acid.
37. A process as claimed in claims 35 & 36 wherein the protic solvent used in the crystallization step (i) is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanόl, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
38. A process as claimed in claims 35 to 37 wherein the base used in neutralization of diastereomeric salt in step (i) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, preferably sodium or potassium hydroxide.
39. A process as claimed in claims 35 to 38 wherein the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
40. A process as claimed in claims 35 to 39 wherein the organic acid used in hydrogenation step (ii) are selected from acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, preferably acetic acid, oxalic acid or mandelic acid.
41. A process as claimed in claims 35 to 40 wherein the mineral acid used in hydrogenation step (ii) is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid.
42. A process as claimed in claims 35 to 41 wherein the metal catalyst used in hydrogenation step (ii) is selected from 2-10% palladium-on-carbon, Raney nickel, preferably 5% palladium-on-carbon.
43. A process as claimed in claims 35 to 42 wherein the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, preferably toluene or heptane.
44. Novel compounds of formula-XXIV,
Figure imgf000046_0001
XXIV
Wherein X = Ms and R = Me or Et Isomer and acid addition salts thereof.
45. A process for the preparation of compound of the formula XXIV which comprises: (i) Resolving the compound of the formula-XX,
Figure imgf000046_0002
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric salt with a base,
Figure imgf000046_0003
XXI (ϋ) Hydrogenating the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of the formula-XXII,
Figure imgf000047_0001
XXII (iii) Reacting the amine of the formula-XXII with metftyl or ethyl acrylate in the presence of a solvent at a temperature in the range of 20-120°C to get the 1,4- addition product of the formula-XXIII,
Figure imgf000047_0002
XXIII (iv) Converting the hydroxy group present in the compound of the formula-XXIII into a leaving group OX with an appropriate reagent in a solvent medium with or without a base at a temperature in the range of -20 to 60 °C to get the compound of formula-XXIV,
Figure imgf000047_0003
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et
46. A process as claimed in claim 45 wherein the chiral acid used in resolution is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-p-toluoyltartaric acid or (+)- tartaric acid, preferably, (+)-Mandelic acid.
47. A process as claimed in claims 45 & 46 wherein the protic solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
48. A process as claimed in claims 45 to 47 wherein the base used in neutralization of diastereomeric salt in step (i) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, preferably sodium or potassium hydroxide.
49. A process as claimed in claims 45 to 48 wherein the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
50. A process as claimed in claims 45 to 49 wherein the organic acid used in hydrogenation step (ii).are selected from acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, preferably acetic acid, oxalic acid or mandelic acid.
51. A process as claimed in claims 45 to 50 wherein the mineral acid used in hydrogenation step (ii) is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid.
52. A process as claimed in claims 45 to 51 wherein the metal catalyst used in hydrogenation step (ii) is selected from 2-10% palladium-on-carbon, Raney nickel, preferably 5% palladium-on-carbon.
53. A process as claimed in claims 45 to, 52 wherein the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1,4-dioxane, acetonitrile, preferably toluene or heptane.
54. A process as claimed in claims 45 to 53 wherein the reagent used in step (iv) for the conversion of the hydroxy group to OX is selected from methanesulfonyl chloride, benzenesulfonyl chloride, p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, preferably, methanesulfonyl chloride or benzenesulfonyl chloride.
55. A process as claimed in claims 45 to 54 wherein the solvent used in step (iv) is selected from methylene chloride, ethylene dichloride, toluene, cylcohexane, heptane, THF, ether, diisopropyl ether etc., preferably, methylene chloride, toluene or heptane
56. A process as claimed in claims 45 to 55 wherein the base used in step (iv) is selected from triethylamine, pyridine, lutidine, sodium or potassium carbonate, or bicarbonate, etc., preferably, pyridine or triethylamine.
57. A process as claimed in claims 45 to 56 wherein the preferred reaction temperature in step (iv) is in the range of -20 to 25°C, more preferably -5 to 15 °C.
58. Novel compound of the formula XXV,
Figure imgf000049_0001
Wherein R = Me or Et
59. A process for the preparation of compound of the formula XXV,
Figure imgf000050_0001
XXV Wherein R = Me or Et which comprises: (i) Resolving the compound of the formula-XX,
Figure imgf000050_0002
XX using a chiral acid in a protic solvent medium to get the chiral amine of formula-XXI after neutralization of the diastereomeric salt with a base,
Figure imgf000050_0003
XXI (ϋ) Hydrogenating the acid addition salt of the resolved amine of formula-XXI using a metal catalyst under heterogeneous conditions to get the secondary amine of the formula-XXII,
Figure imgf000050_0004
XXII (iii) Reacting the amine of the formula-XXII with methyl or ethyl acrylate in the presence of a solvent at a temperature in the range of 20-120°C to get the 1,4- addition product of the formula-XXIII,
Figure imgf000051_0001
XXIII (iv) Converting the hydroxy group present in the compound of the formula-XXIII into a leaving group OX with an appropriate reagent in a solvent medium with or without a base at a temperature in the range of -20 to 60 °C to get the compound of formula-XXIV,
Figure imgf000051_0002
XXIV Wherein X = Ms, Bs, Ts, CF3SO2; R = Me or Et (v) Reacting the compound of the formula-XXIV with a strong base in the presence of a hydrocarbon/ether and / or dipolar aprotic solvent at a temperature in the range of -20 to 40 °C to get the cyclized compound of formula-XXV,
Figure imgf000052_0001
XXV
Wherein R = Me or Et
60. A process as claimed in claim 59 wherein the chiral acid used in resolution is selected from (+)-Mandelic acid, (+)-camphorsulphonic acid, (+)-di-ρ-toluoyltartaric acid or (+)- tartaric acid, preferably, (+)-Mandelic acid.
61. A process as claimed in claims 59 & 60 wherein the protic solvent used in the crystallization step is selected from alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, t-butanol, etc., preferably methanol, ethanol, isopropanol, more preferably isopropanol.
62. A process as claimed in claims 59 to 61 wherein the base used in neutralization of diastereomeric salt in step (i) is selected from sodium or potassium hydroxide, carbonate, bicarbonate, preferably sodium or potassium hydroxide.
63. A process as claimed in claims 59 to 62 wherein the acids used for salt formation during hydrogenation step (ii) are selected from organic or mineral acids.
64. A process as claimed in claims 59 to 63 wherein the organic acid used in hydrogenation step (ii) are selected from acetic acid, propionic acid, oxalic acid, succinic acid, benzoic acid, toluic acid, mandelic acid, tartaric acid, methanesulfonic acid, camphorsulfonic acid, preferably acetic acid, oxalic acid or mandelic acid.
65. A process as claimed in claims 59 to 64 wherein the mineral acid used in hydrogenation step (ii) is selected from hydrochloric- acid, hydrobromic acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid.
66. A process as claimed in claims 59 to 65 wherein the metal catalyst used in hydrogenation step (ii) is selected from 2-10%) palladium-on-carbon, Raney nickel, preferably 5% palladium-on-carbon.
67. A process as claimed in claims 59 to 66 wherein the solvent used in step (iii) is selected from toluene, xylene, cyclohexane, hexane, heptane, methylene chloride, THF, ether, diisopropyl ether, 1 ,4-dioxane, acetonitrile, preferably toluene or heptane.
68. A process as claimed in claims 59 to 67 wherein the reagent used in step (iv) for the conversion of the hydroxy group to OX is selected from methanesulfonyl chloride, benzenesulfonyl chloride, p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, preferably, methanesulfonyl chloride or benzenesulfonyl chloride.
69. A process as claimed in claims 59 to 68 wherein the solvent used in step (iv) is selected from methylene chloride, ethylene dichloride, toluene, cylcohexane, heptane, THF, ether, diisopropyl ether etc., preferably, methylene chloride, toluene or heptane
70. A process as claimed in claims 59 to 69 wherein the base used in step (iv) is selected from triethylamine, pyridine, lutidine, sodium or potassium carbonate, or bicarbonate, etc., preferably, pyridine or triethylamine.
71. A process as claimed in claims 59 to 70 wherein the preferred reaction temperature in step (iv) is in the range of -20 to 25°C, more preferably -5 to 15 °C.
72. A process as claimed in claims 59 to 71 wherein the strong base used in step (v) is selected from sodium hydride, potassium t-butoxide, n-butyl lithium, lithium diisopropyl amide, preferably sodium hydride.
73. A process as claimed in claims 59 to 72 wherein the hydrocarbon solvent used in step (v) is selected from toluene, hexane, heptane, cyclohexane, preferably toluene or cyclohexane.
74. A process as claimed in claims 59 to 73 wherein the ether solvent used in step (v) is selected from diethyl ether, dioxane, THF, methyl t-butyl ether, preferably THF.
75. A process as claimed in claims 59 to 74 wherein the aprotic solvent used in step (v) is selected from dimethylformamide, dimethylacetamide, preferably dimethylformamide.
76. A process as claimed in claims 59 to 75 wherein the preferred temperature of reaction in step (v) is -5 to 25 °C.
77. A process for the preparation of compound of formula-I substantially as described in Examples.
78. Novel intermediates of the formulae XXI, XXII, XXIII, XXIV, and XXV substantially as herein described with reference to Examples.
79. Processes for the preparation of novel intermediates of the formulae XXI, XXII, XXIII, XXIV, and XXV substantially as herein described with reference to Examples.
PCT/IN2004/000247 2003-12-26 2004-08-18 Enantiospecific process for the preparation of paroxetine intermediate WO2005063707A1 (en)

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