Selective olefin metathesis of bifunctional or...

Details Selective olefin metathesis of bifunctional or... Selective olefin metathesis of bifunctional or...

1999-10-15

2002-02-19

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S170000, C526S172000, C526S266000, C526S308000

Reexamination Certificate

active

06348551

ABSTRACT:

The present invention relates to the preparation of cyclic products by selective olefin metathesis of bifunctional or polyfunctional substrates in the presence of one or more homogeneous or heterogeneous metathesis catalysts in a reaction medium, characterized in that the substrates contain two or more functional groups in the form of substituted or unsubstituted alkene or alkyne moieties, and the reaction medium essentially consists of compressed carbon dioxide. The invention further relates to the preparation of cyclic or polymeric products by the process mentioned wherein the reaction temperature and the total pressure are mutually adjusted in such a way that the density of the reaction medium is within a range of d=0.2-1.5 g·cm
−3
, and the product distribution is essentially controlled by the density of the reaction medium. “Olefin metathesis” means the mutual transalkylideneation of alkenes. Reactions of this kind are usually catalyzed by metallic compounds (review: Ivin, K. J.; Mol, J. C.,
Olefin Metathesis and Metathesis Polymerization
, Academic Press, New York, 1997) and find applications in a wide variety of technically important processes. These include the preparation of alkenes, for example, in the Shell higher olefin process (Sherwood, M.,
Chem. Ind.
(London) 1982, 994), in the Phillips triolefin process, and in the production of &agr;,&ohgr;-diolefins (Banks, R. L. et al.,
J. Mol. Catal.
1982, 15, 21). Another application is the ring-opening oligomerization or polymerization of cycloalkenes (ROMP, U.S. Pat. No. 4,567,244) which is used, for example, for the production of Vestenamer® (Dräxler, A., Der Lichtbogen 1986, 35, 24) or Norsorex® (Ohin, R. F., Chemtech 1980, 198). Further, there may be mentioned the oligomerization or polymerization of acyclic dienes (ADMET, Lindmark-Hamberg, M. et al.,
Macromolecules
1987, 20, 2951), the synthesis of carbo- and heterocycles having different ring sizes by ring-closure metathesis (RCM, WO 96/04289, Grubbs, R. H. et al.,
Acc. Chem. Res.
1995, 28, 446), crossed metatheses of different alkenes (Brümmer, O. et al.,
Chem. Eur. J.
1997, 3, 441), and ene-yne metatheses (Kinoshita, A. et al., Synlett 1994, 1020; Kim, S.-H. et al.,
J. Org. Chem.
1996, 61, 1073). Various carbo- or heterocycles having ring sizes of ≧5 prepared by RCM have already been used for the synthesis of natural or synthetic active substances, odoriferous substances and flavors, pheromones, pharmaceuticals, crown ethers etc. (U.S. patent application Ser. No. 08/767.561 of Dec. 16, 1996, Studiengesellschaft Kohle mbH). There may be mentioned, in particular, the efficient synthesis of macrocycles by RCM (Fürstner, A. et al.,
J. Org. Chem.
1996, 61, 3942), which is the basis, inter alia, of several syntheses of the antitumor drug epothilone and its analogues (Bertinato, P. et al.,
J. Org. Chem.
1996, 61, 8000; Nicolaou, K. C. et al.,
Angew. Chem.
1996, 108, 2554; Yang, Z. et al.,
Angew. Chem.
1997, 109, 170; Schinzer, D. et al.,
Angew. Chem.
1997, 109, 543).
The preparation of cyclic compounds from open-chain substrates is a central problem of chemical synthesis. Cyclizations are often performed in an intramolecular ring-closure reaction, proceeding from bifunctional or polyfunctional precursors. The desired ring-closure reactions are always competing with a polymerization of the substrates (“polymers” in this connection means products formed by the linkage of two or more substrate molecules, including, in particular, dimers and oligomers of low molecular weights). This general problem also applies to the preparation of cyclic products by olefin metatheses. If this reaction is performed with bifunctional or polyfunctional substrates in which the mentioned functional groups are alkenes or alkynes, mixtures of the cyclization product and polymers are formed. In Scheme 1, this competition situation is exemplified by the metathesis reaction of the diene 1.
In detail, the product distribution between the polymer and the cyclization product depends on the structure of the substrates, the catalyst used and the reaction conditions. The formation of the cyclization product is favored by performing the reaction in an organic solvent at a high dilution. This applies, in particular, to the preparation of medium-sized (8-11 ring members) and large-sized (≧12 ring members) rings. In general, hydrocarbons (hexane, toluene, xylene, cumene etc.) or chlorinated hydrocarbons (dichloromethane, 1,2-dichloroethane, halobenzenes etc.) are preferred as solvents for olefin metatheses. The large reaction volumes and expensive dosage methods required for achieving the necessary high dilutions limit the maximum yields obtainable per space and time. The separation of the products present in high dilutions from the reaction mixtures further requires time- and energy-consuming separation operations, such as chromatography, rectification or distillation. The thermal stress in distillative separations may adversely affect the quality of the products obtained and often leads to an irreversible deactivation of the catalysts employed. In the synthesis of physiologically active compounds, residual solvents which may not be toxicologically safe represent a particular problem. Also with respect to possible environmental impacts, the use of large amounts of solvents involves drawbacks in terms of process technology. Therefore, methods resulting in a complete or partial elimination of the mentioned solvents are of great technical importance.
Carbon dioxide has been proposed as an ecologically safe reaction medium for metal-catalyzed reactions [reviews: Jessop, P. G. et al.,
Science
1995, 269, 1065; Morgenstern, D. A. et al. in:
Green Chemistry
(Ed.: P. T. Anastas, T. C. Williamson) ACS
Symp. Ser.
262, American Chemical Society, Washington D.C., 1996, p. 132 et seq.; Dinjus, E. et al. in:
Chemistry under Extreme or Non
-
Classical Conditions
(Ed.: R. van Eldik, C. D. Hubbard), Wiley, New York, 1996, p. 219 et seq.]. Metathesis reactions in compressed (gaseous, liquid or supercritical) carbon dioxide are described in WO 96/32421; however, this includes only ring-opening polymerization (ROMP) reactions of cyclic monofunctional alkenes as substrates. We now describe a process for the preparation of chemical products by selective olefin metathesis of bifunctional or polyfunctional substrates in the presence of a homogeneous or heterogeneous metathesis catalyst in a reaction medium, characterized in that the substrates contain two or more functional groups in the form of substituted or unsubstituted alkene or alkyne moieties, and the reaction medium essentially consists of compressed (gaseous, liquid or supercritical) carbon dioxide. In particular, the present invention relates to the preparation of cyclic compounds having ring sizes of n≧5 by the ring-closure metathesis of bifunctional or polyfunctional substrates. Surprisingly, it has been found that cyclic or polymeric products can be selectively obtained with a high selectivity by varying the density of the reaction medium.
Using the present invention, carbo- and heterocycles of arbitrary ring size n (n≧5) including medium-sized (n=8-11) and large-sized (n≧12) rings can be prepared. The solvents used to date in such reactions, which are in part physiologically doubtful and environmentally harmful (e.g., aromatics or chlorinated hydrocarbons), are thus completely or substantially replaced by a nontoxic, noncombustible, inexpensive reusable reaction medium. Performing the reaction in compressed carbon dioxide has the further consequence that substituents at the substrates are tolerated which are not compatible with the olefin metathesis in conventional solvents. Further, the processing of the reaction mixtures is substantially simplified due to the special solvent properties of compressed carbon dioxide, for example, by segregating the products wholly or partially from the reaction mixture, or by separating them wholly or partially from the catalyst using the extractive propertie

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