Title of Invention

A PROCESS FOR THE PREPARATION OF A NOVEL HETEROGENEOUS OSMATE CATALYST

Abstract A process for the preparation of a novel heterogeneous osmate catalyst of the general formula (S-NR3)2OsO4 nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules by reacting potassium osmate with supported quaternary ammonium species in an aqueous solvent at a temperature in the range of 20 to 30°C for a period in the range of 5-24 hours under nitrogen atmosphere followed by washing to obtain the desired catalyst.
Full Text The present invention relates to a process for the preparation of vicinal diols. The present invention particularly relates to a process for the preparation of supported osmates of the formula ((S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules and use thereof in the preparation of vicinal diols by asymmetric dihydroxylation (AD) of olefins in presence of cinchona alkaloid compounds. Background of the invention
The asymmetric dihydroxylation of olefins in the presence of cinchona alkaloid results in products that are important intermediates in the preparation of various drugs and chemicals. For example, the products of cinnamic acid esters are intermediates for taxol side chain, an anticancer drug, diltiazem, calcium antagonist and chloramphenicol, an antibiotic, proranolol, a (3 blocker can also be derived from diols obtained through this method.
These are serious disadvantages in performing the catalytic AD reaction with homogeneous system in the manufacture of vicinal diols due to presence of toxic remnants of osmium in products and high cost of osmium tetra oxide or potassium osmate dehydrate. By employing the heterogeneous catalytic system, the cost naturally comes down due to easy recovery of the catalyst and very insignificant loss of osmium tetra oxide, when compared with homogeneous system. The products thus obtained using heterogeneous catalyst system are benign in the sense that the presence of osmium in minor impurities in the dihydroxylated products is also precluded.
US Patents 4,871,855 and 5,260,421 disclose a process for the asymmetric dihydroxylation of olefins using osmium tetra oxide and cinchona alkaloids using a homogeneous catalyst system. These processes involve cumbersome recovery of the osmium catalyst from the reaction mixture, generation of toxic waste and the potential presence of toxic osmium in the product.
US Patent 5,516,929 discloses asymmetric dihydroxylation of olefins using osmium tetra oxide and polymer bound cinchona alkaloids in a heterogeneous system. The quantitative recovery of the toxic osmium catalyst, lower enantioselectivity and reduction in activity and enantioselectivity in each recycle experiments are some of the disadvantages associated with this process.
US Patent 5,968,867 discloses the asymmetric dihydroxylation of olefins using osmium tetra oxide and silica gel supported bis-cinchona alkaloid derivatives in a heterogeneous system. The quantitative recovery of the toxic osmium catalyst is difficult and
a reduction in activity and enantioselectivity of the catalyst is observed in each and every recycle experiment.
European Patent 940,170 A2 describes the catalytic asymmetric dihydroxylation of alkenes using a polymer supported osmium catalyst. The drawbacks of this process are that higher amounts of catalyst are required (5 mol%), the reaction time is very long and expensive polymers are used as supports. Objects of the invention
The main object of the invention is to provide a heterogeneous recyclable supported osmate of the general formula (S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules and use thereof in the preparation of vicinal diols by asymmetric dihydroxylation (AD) of olefins in presence of cinchona alkaloid compounds. It is another object of the invention to provide a process for the preparation of a novel heterogeneous recyclable supported osmate of the general formula ((S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules and use thereof in the preparation of vicinal diols which process.
It is another object of the invention to provide a environmentally friendly process for the asymmetric dihydroxylation of olefins to obtain vicinal diols using a novel heterogeneous supported osmate of the invention.
It is a further object of the invention to provide a process for the preparation of vicinal diols with good enantioselectivity, activity and yield by the asymmetric dihydroxylation of olefins using a novel osmate catalyst of the invention.
It is yet another object of the invention to provide a process for the preparation of vicinal diols by the asymmetric dihydroxylation of olefins in the presence of cinchona alkaloids and derivatives thereof, which process is simple, economical and results in a product with no traces of toxic osmium therein.
It is a further object of the invention to provide a process for the preparation of vicinal diols by the asymmetric dihydroxylation of olefins in the presence of cinchona alkaloids and derivatives thereof wherein the catalyst is capable of recycle several times without substantial loss of activity or in yield of product. Summary of the invention
These and other objects of the invention are achieved by using the novel supported heterogeneous osmate catalyst of the general formula ((S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules for the asymmetric
dihydroxylation of olefins in the presence of cinchona alkaloids to obtain vicinal diols with good yield and selectivity.
The novelty of the invention lies in the supported osmate used as catalyst and in the preparation of vicinal diols in the presence of cinchona alkaloids or derivatives employing oxidants.
Accordingly, the present invention provides a supported osmate of the general formula (S-NR3)2Os04.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules.
In one embodiment of the invention, the support is selected from resin or silica.
In another embodiment of the invention, R is selected from methyl, ethyl, propyl, butyl and like alkyl groups.
In a further embodiment of the invention, the osmium content in the catalyst is in the range of 5 to 30%.
In a further embodiment of the invention, the support S used has charge balancing anions selected from chloride, bromide, iodide, fluoride, hydroxide and acetate.
Accordingly, the present invention provides a process for the preparation of a novel heterogeneous osmate catalyst characterized in that the said process comprising reacting potassium osmate with supported quaternary ammonium species in an aqueous solvent at a temperature in the range of 20 to 30°C for a period in the range of 5-24 hours under nitrogen atmosphere followed by washing to obtain the desired catalyst.
In one embodiment of the invention, the osmium content in the catalyst is in the range of 5 to 30%.
In a further embodiment of the invention, the support S used has charge balancing anions selected from chloride, bromide, iodide, fluoride, hydroxide and acetate.
In one embodiment of the invention, the support is selected from resin or silica.
In another embodiment of the invention, R is selected from methyl, ethyl, propyl, butyl and like alkyl groups.
The present invention also provides a process for the preparation of vicinal diols comprising asymmetrically dihydroxylating the corresponding olefin in the presence of a cinchona alkaloid using an oxidant such as herein described in a solvent system consisting of water and at least one of acetone, acetonitrile and t-butanol, in a ratio of water: acetone, wateracetonitrile and watert-butanol of 1:1 to 1:3, and water:acetone:acetonitrile in a ratio of 1:1:1; at a temperature in the range of -70 to 100°C for a period in the range of 0.5 to 24
hours, and in the presence of a catalytic amount of a heterogeneous supported osmate catalyst of the general formula (S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules, and recovering the pure vicinal diol by any conventional method.
In one embodiment of the invention, the osmium content in the catalyst is in the range of 5 to 30%.
In a further embodiment of the invention, the support S used has charge balancing anions selected from chloride, bromide, iodide, fluoride, hydroxide and acetate.
In one embodiment of the invention, the support is selected from resin or silica. In another embodiment of the invention, R is selected from methyl, ethyl, propyl, butyl and like alkyl groups.
In yet another embodiment of the invention, the amount of supported osmate used in the reaction is 0.01 to 10 mol% of osmium content with respect to the substrate.
In another embodiment of the invention, the catalyst is recovered from the reaction system by any conventional process and recycled to the reaction system several times.
In a further embodiment of the invention, the oxidant used is selected from the group consisting of N-methylmorpholine N-oxide (NMO), trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide, potassium ferricyanide, sodium periodate and molecular oxygen.
In yet another embodiment of the invention, the cinchona alkaloid and derivatives thereof comprise a monomeric and polymeric chiral ligand.
In a further embodiment of the invention, the chiral ligand is selected from the group consisting of (DHQD)2PHAL, (DHQD)2PYR, (DHQD)2AQN, DHQD-Oac, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND and pseudoenantiomeric forms thereof. Detailed description of the invention
The novelty of the invention lies in the supported osmate used as catalyst and in the preparation of vicinal diols in the presence of cinchona alkaloids or derivatives employing oxidants.
The novel supported osmate of the general formula (S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules. The support is preferably selected from resin or silica. R is preferably selected from methyl, ethyl, propyl, butyl and like alkyl groups. The osmium content in the catalyst is generally in the range of 5 to 30%. The support S used may contain charge balancing anions selected from chloride, bromide, iodide, fluoride, hydroxide and acetate.
The heterogeneous osmate catalyst of the general formula (S-NR3)2OsO4.nH2O wherein S is a support, R is an alkyl group, n is the number of water molecules is prepared by reacting potassium osmate with supported quaternary ammonium species in an aqueous solvent at a temperature in the range of 20 to 30°C for a period in the range of 5 - 24 hours under nitrogen atmosphere followed by washing to obtain the desired catalyst.
The process for preparation of vicinal diols comprises asymmetrically dihydroxylating the corresponding oletin in the presence of a cinchona alkaloid using an oxidant in a solvent system consisting of water and at least one of acetone, acetonitrile and t-butanol, in a ratio of wateracetone, water:acetonitrile and watert-butanol of 1:1 to 1:3, and water:acetone:acetonitrile in a ratio of 1:1:1; at a temperature in the range of-70 to 100°C for a period in the range of 0.5 to 24 hours, and in the presence of a catalytic amount of a heterogeneous supported osmate catalyst of the general formula (S-NR3)2OsO4nH2O where S is a support, R is an alkyl group, n is the number of water molecules, and recovering the pure vicinal diol by any conventional method. The amount of supported osmate used in the reaction is 0.01 to 10 mol% of osmium content with respect to the substrate.
The catalyst can be recovered from the reaction system by any conventional process and recycled to the reaction system several times without any substantial loss of activity or of yield of the product. The oxidant used is selected from N-methylmorpholine N-oxide (NMO), trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide, potassium ferricyanide, sodium periodate and molecular oxygen. The cinchona alkaloid and derivatives thereof comprise a monomeric and polymeric chiral ligand such as for example (DHQD)2PHAL, (DHQD)2PYR, (DHQD)2AQN, DHQD-OAc, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND and pseudoenantiomeric forms thereof. Scientific explanation
In the present invention, novel supported osmates were prepared for the first time using the anion exchange method from the supported quaternary ammonium species. The osmate anions present on the support are responsible for the dihydroxylation activity of the reaction. The activity of the supported osmate is similar or higher than the homogeneous counterparts. Without wishing to be bound by any theory, it is believed that the higher activity is ascribed to the support effect. The large positive potential of OsO42- support surface induces polarisation of N→O bond and facilitates oxygen transfer.
Higher yields and enantioselectivities are obtained with supported osmate catalysts used in the asymmetric dihydroxylation of olefins in aqueous organic solvents. Since the
dihydroxylated products are important intermediates for the preparation of drugs and Pharmaceuticals, this invention is timely and appropriate. Therefore, supported osmate is a better option for the synthesis of vicinol diols. The supported osmate catalysts prepared from various supports offered good yields and enantioselectivies in presence of cinchona alkaloids. Thus this invention offers the best techno-economic route for the synthesis of vicinol diols, intermediates for the preparation of drugs and pharmaceuticals.
Supported osmates are prepared as examplified and used in catalytic amounts for preparing vicinol diols by asymmetric dihydroxylation of olefins employing oxidants in presence of cinchona alkaloid compounds in a heterogeneous way as described in the examples.
The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the invention.
Preparation of Catalysts
Example 1 Resin-OsO.4: Resin was obtained by quaternization of triethylamine (2.1 mL, 21
mmol) with 1 g of chloromethylated styrene-divinylbenzene copolymer (Merrifield resin, capacity ~2.1 mequiv/g) in chloroform (20 mL) under reflux for 24 h. 1 g of quaternary ammonium resin was suspended in 100 mL of 0.8 mmol aqueous potassium osmate solution and stirred at 25 °C for 12 h under nitrogen atmosphere. The solid catalyst was filtered, washed thoroughly with 300 mL of water and vacuum dried to obtain Resin-OsCU (0.641 mmol of Os per g).
Example 2
SiO2-OsO4; Modified silica was obtained by quaternisation of triethylamine (0.7 mL,
7 mmol) with bromopropylsilica (capacity 0.7 mequiv/g) in chloroform (20 mL) under reflux for 24 h. 1 g of quaternary ammonium silica was suspended in 100 mL of 0.33 mmol aqueous potassium osmate solution and stirred at 25 °C for 12 h under nitrogen atmosphere. The solid
catalyst was filtered, washed thoroughly with 300 mL of water and vacuum dried to obtain SiO2-OsO4 (0.317 mmol of Os per g).
Asymmetric Dihydroxylation of Olefins
The asymmetric dihydroxylation reaction of olefins was performed using the following method in order to evaluate supported osmates of the present invention.
Supported osmate (0.01 eq. wt. of osmium content), bis-cinchona alkaloid (DHQD)2PHAL (0.01 Eq. Wt.) and N-methylmorpholine-N-oxide (1.5 Eq. Wt.) were stirred in the mixed solvent of water/ace tone/acetonitrile (in the volume ratio of 1:1:1). To this mixture was added an olefin (1.0 Eq. Wt) slowly for a period of 12 h. After the reaction, the supported osmate catalyst was filtered off and washed with ethyl acetate. The combined filtrates were concentrated under reduced pressure. The chiral ligand was recovered from the aqueous layer after acidification (IN HC1). The concentrated organic layer was purified to afford the corresponding cis-diol by using conventional processes. The yield and the optical purity of the product were determined.
Catalytic asymmetric dihydroxylation of olefins using N-methylmorpholine-N-oxide as a co-oxidant
Example 3
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by using Resin-OsO4 : Resin-OsO4 (0.01 Eq. Wt.), Hydroquinidine 1,4-phthalazinediyl diether (DHQD)2PHAL (0.01 Eq. Wt.) and N-methylmorpholine-N-oxide (1.5 Eq. Wt.) were stirred in the mixed solvent of water/acetone/acetonitrile (in the volume ratio of 1:1:1). To this mixture was added trans-stilbene (1.0 Eq. Wt) and stirred at room temperature for 6 hours. After the reaction, supported osmate catalyst was filtered off and washed with methanol. The combined filtrates were concentrated under reduced pressure. The chiral ligand was recovered from the aqueous layer after acidification (IN HC1). The pure product was obtained by removing the solvent at reduced pressure followed by column chromatography. (R,R)-(+)-l,2-diphenyl-l,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 96%) [«]D +92.44 (c 1.0, EtOH): e.e.=99.4%
Example 4
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by reusing Resin-OsO4 which had been used in Example 3 without further addition of osmate catalyst. The reaction was performed using an identical process as in Example 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 95%) [α]D+92.16 (c 1.0, EtOH): e.e.=99.2%.
Example 5
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by reusing Resin-OsO4 which had been used in Example 4 without further addition of supported osmate catalyst. The reaction was performed by using an identical process as in Example 3 (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 97%) [α]D+92.16 (c 1.0, EtOH): e.e.=99.1%.
Example 6
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by reusing Resin-OsO4 which had been used in Example 5 without further addition of supported osmate catalyst. The reaction was performed by using an identical process as in Example 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 94% [α]D+92.25 (c 1.0, EtOH): e.e.=99.2%.
Example 7
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by reusing Resin-OsO4 which has been used in Example 6 without further addition of Supported osmate catalyst. The reaction was performed by using an identical process as in Example 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 96%) [α]D+92.81 (c 1.0, EtOH): e.e.=99.8%.
Example 8
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by reusing Resin-OsO4 which had been used in Example 7 without further addition of Supported osmate catalyst. The reaction was performed by using an identical process as in Example 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 98%) [α]D+92.25 (c 1.0, EtOH): e.e.=99.2%.
Example 9
Catalytic asymmetric dihydroxylation reaction of trans-stilbene by SiO2-OsO4 The reaction was performed by using an identical process as in Example 3. (R,R)-(+)-l,2-diphenyl-l,2-ethandiol of more than 99.0% of enantiomeric excess was obtained (yield 97%) [∞]D +92.34 (c 1.0, EtOH): e.e =99.3%
Example 10
Catalytic asymmetric dihydroxylation reaction of styrene by using Resin-OsO4
The reaction was performed by using an identical process as in Example 3 except slow
addition of olefin with a reaction time of 12 hours. (R)-phenyl-l,2-ethanediol of more than
95.0% of enantiomeric excess was obtained (yield 94%)
[∞]D -34.29 (c 1.32, EtOH): e.e.=95.7%
Example 11
Catalytic asymmetric dihydroxylation reaction of trans-beta.-methyl styrene by using Resin-
Os04
The reaction was performed by using an identical process as in Example 3 except slow
addition of olefin with a reaction time of 12 hours. (R,R)-l-phenyl-l,2-propanediol of more
than 98.0% of enantiomeric excess was obtained (yield 97%)
[∞]D -30.50 (c 1.32, EtOH): e.e.=98.1%
Example 12
Catalytic asymmetric dihydroxylation reaction of methyl trans-cinnamate by using Resin-OsO4.
The reaction was performed by using an identical process as in Example 3 except slow addition of olefin with a reaction time of 12 hours. (2S,3R)-2,3-dihydroxy-3-phenylpropionate of more than 99% of enantiomeric excess was obtained (yield 96%) [∞]D -10.6 (c 1.0, CHC13): e.e.=99%
Example 13
Catalytic asymmetric dihydroxylation reaction ofallyl 1-naphthyl ether by using Resin-OsO4 The reaction was performed by using an identical process as in Example 3 except slow addition of olefin with a reaction time of 12 hours. 2,3-dihydroxypropyl-l-naphthyl ether of more than 77.0% of enantiomeric excess was obtained (yield 94%) [∞]D +5.18 (c 1.0, CH3OH): e.e.=77.4%
Example 14
Catalytic dihydroxylation reaction of trans-stilbene by using Resin-OsO4:
Resin-OsO4 (0.01 Eq. Wt.), N-methylmorpholine-N-oxide (1.5 Eq. Wt.) and trans-stilbene (1.0 Eq. Wt) in the mixed solvent of water/acetone/acetonitrile (in the volume ratio of 1:1:1) were stirred at room temperature for 6 hours. After completion of the reaction, the catalyst was filtered off and washed with ethyl acetate. The combined filtrates were concentrated under reduced pressure. The pure product, l,2-diphenyl-l,2-ethandiol was obtained by removing the solvent at reduced pressure followed by column chromatography. (yield 93%).
The experimental results in the Examples 3 to 14 were tabulated in Table 1&2.
Table 1. Reuse of Resin-OsO4 for asymmetric dihydroxylation reaction of trans-stilbene
(Table Removed)
Table 2. Catalytic asymmetric dihydroxylation reaction of olefins by using Resin-OsO4
(Table Removed)
Equivalent weight ratio of the reactants = olefin: osmium: cinchona alkaloid 1:0.01:0.01, reaction temperature 25°C.
b Yield percent after the separation by using column chromatography.
c % e,e.(e.e. means enantiomeic excess) was determined by HPLC analysis using chiral columns d absolute configuration was compared with the [ a ]D values in the literature.
The main advantages of the present invention are:
1. A novel and ecofriendly process for asymmetric dihydroxylation of olefins is presented.
2. The present process dispenses the use of soluble, toxic osmium tetraoxide or potassium
osmate dihydrate instead heterogeneous reusable supported osmates are used.
3. Supported osmates are prepared and used for asymmetric dihydroxylation of olefins as
heterogeneous catalysts. The use of heterogeneous supported osmates precludes the
presence of osmium in traces with product.
4. The enantioselectivity and the yields are good.
5. The work-up procedure is simple.
6. The catalyst is subjected to many recycles, which displayed consistent activity.
7. The present process is environmentally safe since there is no disposal problem.
8. The process is economical.



We claim :
1 . A process for the preparation of a novel heterogeneous osmate catalyst characterized in that the said process comprising reacting potassium osmate with supported quaternary ammonium species in an aqueous solvent at a temperature in the range of 20 to 30°C for a period in the range of 5-24 hours under nitrogen atmosphere followed by washing to obtain the desired catalyst.
2. A process as claimed in claim 1 wherein the osmium content in the
catalyst is in the range of 5 to 30%.
3. A process for the preparation of a novel heterogeneous osmate catalyst
substantially as herein described with reference to the examples.

Documents:

853-del-2001-abstract.pdf

853-del-2001-claims.pdf

853-del-2001-correspondence-others.pdf

853-del-2001-correspondence-po.pdf

853-del-2001-description (complete).pdf

853-del-2001-form-1.pdf

853-del-2001-form-18.pdf

853-del-2001-form-2.pdf

853-del-2001-form-3.pdf

853-del-2001-petition-137.pdf

853-del-2001-petition-138.pdf


Patent Number 232491
Indian Patent Application Number 853/DEL/2001
PG Journal Number 13/2009
Publication Date 27-Mar-2009
Grant Date 17-Mar-2009
Date of Filing 16-Aug-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI- 110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 BOYPATI MANORANJAN CHOUDHARY INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY UPPAL ROAD, HYDERABAD
2 NAIDU SREENIVASA CHWDHARY INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY UPPAL ROAD, HYDERABAD
3 MANNIPALLY LAKSHMI KANTAM INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY UPPAL ROAD, HYDERABAD
4 KONDAPURAM VIJAYA RAGHAVAN INDIAN INSTITUTE OF CHEMICAL TECHNOLOGY UPPAL ROAD, HYDERABAD
PCT International Classification Number B01J 21/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA