Preparation of new layered double hydroxides exchanged with...

Details Preparation of new layered double hydroxides exchanged with... Preparation of new layered double hydroxides exchanged with...

2000-11-22

2002-05-14

Shaver, Paul F. (Department: 1621)

Harvesters

C423S594120, C423S599000, C423S600000, C423S593100, C568S853000, C568S860000

Reexamination Certificate

active

06387033

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to preparation of layered double hydroxides exchanged with osmate (LDH-osmates) useful as recyclable catalysts for preparing vicinal diols. More particularly the present invention relates to preparation of layered double hydroxides exchanged with osmate of the formula [M
II
(1−x)
M
III
x
(OH)
2
][OsO
4
2−
]
x/2
.zH
2
O wherein M
II
is a divalent cation (Mg
2+
, Mn
2+
, Fe
2+
, Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
or Ca
2+
); M
III
is a trivalent ion (Al
3+
, Cr
3+
, Mn
3+
, Fe
3+
, Co
3+
or Ni
3+
), x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4; and methods of preparation and use thereof. The LDH-osmates of this invention are recyclable catalysts for preparing vicinal diols by asymmetric dihydroxylation (AD) of olefins in presence of cinchona alkaloid compounds.
BACKGROUND OF THE INVENTION
This invention particularly relates to an eco-friendly process employing recyclable LDH-osmates as heterogeneous catalysts in place of soluble osmium catalysts for preparing vicinal diols by asymmetric dihydroxylation of olefins in presence of cinchona alkaloid compounds. The dihydroxylated products are important intermediates for the preparation of drugs and pharmaceuticals. For example the products of cinnamic acid esters are intermediates for taxol side chain, an anticancer drug, diltiazem, calcium antagonist and chloramphenicol, an antiboitic. Propranolol, a &bgr; blocker can also be derived from the diol obtained through this method.
There 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 tetroxide or potassium osmate dihydrate. By employing the heterogeneous catalytic system, the cost naturally comes down due to easy recovery and recyclability of the catalyst for number of recycles and very insignificant loss of osmium tetroxide, when compared with homogenous 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.
Reference is made to U.S. Pat. Nos. 4,871,855 and 5,260,421 wherein asymmetric dihydroxylation of olefins are carried by osmium tetroxide and cinchona alkaloids in homogeneous way. The inherent disadvantages in this process are cumbersome procedure for the recovery of the osmium catalyst from the reaction mixture, generation of toxic waste and possibility of presence of toxic osmium in traces in the product.
Reference is made to U.S. Pat. No. 5,516,929 wherein asymmetric dihydroxylation of olefins are carried by osmium tetroxide and polymer-bound cinchona alkaloids in heterogeneous way. The drawbacks are difficulty in quantitative recovery of toxic osmium catalyst, lower enantioselectivity and reduction in activity and enantioselectivity in each and every recycle experiments.
Reference is made to U.S. Pat. No. 5,968,867 wherein asymmetric dihydroxylation of olefins are carried by osmium tetroxide and silicagel supported bis-cinchona alkaloid derivatives in heterogeneous way. The drawbacks are difficulty in quantitative recovery of toxic osmium catalyst and reduction in activity and enantioselectivity in each and every recycle experiments.
Reference is made to European patent EP 940,170 A2 wherein catalytic asymmetric dihydrpxylation of alkenes are carried by using a polymer-supported osmium tetroxide catalyst. The drawbacks are requiring higher amount of catalyst (5 mol %/), longer reaction time and use of expensive polymer as a support.
OBJECTS OF THE INVENTION
The main object of the present invention is to prepare a heterogeneous recyclable LDH-osmates and to use in catalytic amounts for preparing vicinol diols by asymmetric dihydroxylation of olefins employing oxidants in presence of cinchona alkaloid compounds which obviates the drawbacks as detailed above.
Another object of the present invention is LDH as synthesized having interstitial anions such as chloride, nitrate, carbonate, sulfate or calcination of LDH having the said interstitial anions at temperatures in the range of 350 to 550° C. are used as precursors for the preparation of LDH-osmates.
Still another object of the present invention is to recover the heterogeneous LDH-osmates used in asymmetric dihdroxylation by simple filtration and reuse for number of cycles with consistent activity and enantioselectivity.
Still another object of the present invention is the quantity of LDH-osmate used in the reaction is 0.01 to 3 mol % of osmium with respect to the substrate.
Still another object of the present invention is wherein the co-oxidant is N-methylmorpholine N-oxide (NMO), trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide, potassium ferricyanide, sodium periodate or molecular oxygen.
Still another object of the present invention is the chiral ligand is monomeric or polymeric, preferably hydroquinidine 1,4-phthalazinediyl diether (DHQD)
2
PHAL), hydroquinidine 2,5-diphenyl-4,6-pyrimidinediyl diether ((DHQD)
2
PYR), hydroquinidine (anthraquinone-1,4-diyl) diether ((DHQD)
2
AQN), hydroquinidine acetate (DHQD-OAc), O-(4-chlorobenzoyl) hydroquinidine (DHQD-CLB), hydroquinidine 9-phenanthryl ether (DHQD-PHN), hydroquinidine 4-methyl-2-quinolyl ether (DHQD-MEQ) or the other pseudoenantiomeric forms of these ligands, etc.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a LDH-osmate useful as a catalyst having the formula [M
II
(1−x)
M
III
x
(OH)
2
][OsO
4
2−
]
x/2
.zH
2
O wherein M
II
is a divalent cation selected from the group consisting of Mg
2+
, Mn
2+
, Fe
2+
, Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
and Ca
2+
and M
III
is a trivalent ion selected from the group consisting of Al
3+
, Cr
3+
, Mn
3+
, Fe
3+
and Co
3+
, x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4.
In another embodiment, the present invention relates to a process for the preparation of the catalyst LDH-osmate of the formula [M
II
(1−x)
M
III
x
(OH)
2
][OsO
4
2−
]x/2
.zH
2
O wherein z is the number of water molecules, the said process comprising reacting potassium osmate of formula K
2
OsO
4
2H
2
O with a LDH of formula [M
II
(1−x)
M
III
x
(OH)
2
][A
n−
]
x

.zH
2
O where M
II
is a divalent cation selected from the group consisting of Mg
2+
, Mn
2+
, Fe
2+
, Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
and Ca
2+
and M
III
is a trivalent ion selected from the group consisting of Al
3+
, Cr
3+
, Mn
3+
, Fe
3+
and Co
3+
, x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4, in an aqueous solvent at a temperature ranging between 20 to 30° C. for a period of 5 to 24 h under the nitrogen atmosphere followed by filtration to obtain the desired catalyst.
In yet another embodiment, the present invention relates to a method for the preparation of vicinal diols using the recyclable catalyst LDH-osmates of the formula [M
II
(l−x)
M
III
x
(OH)
2
][OsO
4
2−
]
x/2
.zH
2
O wherein M
II
is a divalent cation (Mg
2+
, Mn
2+
, Fe
2+
, Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
or Ca
2+
); M
III
is a trivalent ion (Al
3+
, Cr
3+
, Mn
3+
, Fe
3+
or Co
3+
), x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4, in catalytic amounts by asymmetric dihydroxylation of olefins using standard methods employing an oxidant in the presence of a cinchona alkaloid compound in a sol

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