Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2001-03-06
2003-11-04
Rotman, Alan L. (Department: 1625)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C549S523000
Reexamination Certificate
active
06642170
ABSTRACT:
The present invention relates to novel solid oxidation catalysts which make possible in particular the oxidation of prochiral compounds, in particular the asymmetric epoxidation of prochiral olefinic double bonds, more particularly of a carbinol compound exhibiting an ethylenic double bond separated from the carbinol group by 0 to 1 C, preferably those of allyl alcohols, to their method of preparation and the use of these solid catalysts in epoxidation reactions.
The introduction of a chiral center onto organic molecules has quite considerable industrial potentialities. This is because natural products are normally chiral, with only one enantiomer exhibiting a useful biological activity. Medicaments, agrochemicals, cosmetics or more generally any molecule which is used in life sciences generally belong to this family of chiral compounds with one or more centers of asymmetry. The separation of the enantiomers from a racemic mixture is expensive, lengthy and not economically profitable. One of the solutions envisaged for improving this irrefutable fact was to find catalysts, which are predominantly homogeneous. These catalysts are generally transition metal complexes which exhibit chiral ligands. Numerous enantioselective catalytic reactions exist.
In particular, the synthesis of enantiopure epoxyalcohols, used in particular as precursors of active principles for pharmaceutical products, is very important industrially (B. E. Rossiter “
Asymmetric Synthesis
”, Academic Press, 1985, vol. 5, pp. 193-246; M. Bulliard and W. Shum, “
Proceedings of the Chiral
'95
USA symposium
” 1995, pp. 5-8; U.S. Pat. No. 4,764,628).
The catalysts currently known for reactions of this type are generally chiral titanium compounds used in the homogeneous liquid phase, according to the principle proposed by Katsuki and Sharpless (
J. Am. Chem. Soc
., 1980, 102, 5974 and U.S. Pat. No. 4,471,130), and cannot be reused (in this document, the chiral compounds can also be tantalum, zirconium, hafnium, niobium, vanadium and molybdenum compounds and the like). See also Johnson and Sharpless “
Comprehensive Organic Synthesis
”, Pergamon Press, 1991, vol. 7, pp. 389-436 and “
Catalytic Asymmetric Synthesis
”, edited by I. Ojima, VCH, 1993, 103-158; Gao, Sharpless et al.,
J. Am. Chem. Soc
., 1987, 109, 5765-5780. However, these catalysts cannot be easily separated from the reaction medium and their separation is, in some cases, particularly harmful to the reaction yield. Furthermore, they cannot be recycled and they cannot be used in a continuous process.
Farrall et al. (
Nouv. J. Chim
., 1983, 7, 449) describe a tartrate grafted onto a polystyrene resin. A titanium alkoxide was grafted onto such a solid and similar results but ones much inferior to those described by Sharpless et al. were obtained. Another publication by Choudary et al. (
J. Chem. Soc., Chem. Commun
., 1990, 1186) also described the incorporation of titanium-based Sharpless complexes in a clay of montmorillonite type. The solid proved to be active in asymmetric epoxidation but was not recycled. A publication by Adam, Corma et al. (
J. Mol. Catal. A
., 1997, 117, 357) reports diastereoselective and non-enantioselective epoxidations of allyl alcohols with aqueous hydrogen peroxide solution catalyzed by titanium-comprising zeolites. However, in this case, the starting allyl alcohols are already chiral and the catalysts achiral. These catalysts were not recycled.
A. Corma et al. (
J. Mol. Catal. A
., 1996, 107, 225-234) have proposed a molybdenum catalyst supported in a zeolite with a chiral ligand. It would be possible to recycle this catalyst but its enantioselectivity is low.
An object of the present invention is to provide novel solid oxidation catalysts which can be easily and efficiently recycled.
A more particular object of the present invention is to provide heterogeneous catalysis for the oxidation of prochiral compounds which combines the following properties:
performances (rate of reaction, activity per catalytic site, reaction yield and selectivity, enantiomeric excess obtained) equal to or superior to those of the homogeneous catalysts currently used,
ease of separation from the reaction medium,
reusable, while retaining the performances, and
optionally usable in a continuous process.
A more particular object of the invention is to provide such heterogeneous catalysis for the asymmetric epoxidation of prochiral olefinic double bonds, in particular those of allyl alcohols.
A first subject-matter of the present invention is a solid oxidation catalyst comprising a metal compound of a pentavalent or hexavalent metal M, selected from the group consisting of tantalum, vanadium, niobium, chromium, molybdenum and tungsten, grafted to the surface of a solid oxide by at least one, preferably one, covalent bond between an oxygen atom of the solid oxide and the metal atom M, the grafted metal compound exhibiting at least two alkoxy groups bonded to the metal via the oxygen atom, preferably at least one of these alkoxy groups being chiral.
The preferred metals are tantalum, vanadium and niobium. The most preferred metal is tantalum.
The alkoxy groups OR bonded to the metal M via the oxygen atom are identical or different (different means that at least one of the R radicals is different from the others). The R radicals are C
1
to C
30
, preferably C
1
to C
8
, more preferably still C
1
to C6, hydrocarbonaceous chains which can be aliphatic or unsaturated, optionally cyclic, in particular aromatic, and which can optionally be functionalized, for example by halide, alcohol or ester functional groups and the like. The R radicals are preferably selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, vinyl, allyl, phenyl or trialkylsilyl (R
3
Si—; R=Me, Et, i-Pr or n-Bu).
According to a preferred form of the invention, at least 2 alkoxy groups bonded to the metal M belong to a polyol unit, in particular a triol or diol unit, preferably a diol unit. These polyol units confer on the catalyst a chiral group of high stability which cannot be easily displaced or exchanged under the effect of other molecules when the catalyst will be employed in an epoxidation reaction.
Mention may be made, among the chiral diol units which come under the present invention, of:
1,2-propylene glycol
2,3-butanediol
3,4-dimethyl-3,4-hexanediol
4,5-octanediol
2,3-hexanediol
1,3-di(p-nitrophenyl)propane-1,2-diol
2,4-pentanediol
tartaric acid esters, for example:
dimethyl tartrate
diethyl tartrate
diisopropyl tartrate
distearyl tartrate
diphenyl tartrate
tartaric acid diamide
N,N-dimethyl tartaric acid diamide
trans-1,2-cyclopentanediol
diethyl 1,2-cyclohexanediol-1,2-dicarboxylate
dimethyl 2,4-dihydroxyglutarate
ethyl N,N-diethyl tartrate monoamide
2,5-dioxo-3,4-octanediol
1,2-bisacetylethylene glycol
bis-2,2′-(2-hydroxycaprolactone)
binaphthol
1,2-bis(methoxyphenyl)ethane-1,2-diol.
Diethyl or diisopropyl tartrate units are preferred.
Generally, the metal compound grafted onto the solid oxide preferably comprises 4 alkoxy groups when the metal M is selected from tantalum, vanadium or niobium and 4 or 5 alkoxy groups when the metal is selected from chromium, molybdenum or tungsten, those optionally belonging to a polyol unit being included within these values.
The oxidation catalysts according to the invention can also be defined by their process of preparation. It is possible, for the preparation of the catalyst, to preferably start from a complex of the metal M.
The precursor complexes of tantalum or another metal, which are used to create the bond between the metal M and the oxygen of the support (solid oxide), comprise appropriate identical or different ligands, at least one of which can be substituted by an oxygen of the solid oxide, for example an oxygen of a siloxy group in the case of silica, for the formation of at least one covalent bond between an oxygen atom of the solid oxide and the metal atom M. The ligands can be in all or part, in particular completely, alkoxy groups as described above, including polyol gr
Basset Jean-Marie
De Mallman Aimery
Meunier Damien
Piechaczyk Arnaud
Centre National de la Recherche Scientifique (C.N.R.S.)
Covington Raymond
Rotman Alan L.
Young & Thompson
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