Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2000-02-22
2001-11-13
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S162000, C502S167000, C502S200000, C548S303100, C548S335100, C548S343100, C548S345100, C548S347100
Reexamination Certificate
active
06316380
ABSTRACT:
The present invention relates to novel catalysts which can be used for chemical synthesis in the polymer and the fine chemical industry, and to novel and eminently useful N-heterocyclic carbenes used in forming such catalysts.
BACKGROUND
Metal catalyzed coupling reactions of aryl bromides, aryl iodides, and aryl pseudohalides (e.g., triflates) with various substrates is a general method employed for the formation of C—C and C—N bonds. Prior art methods generally cannot employ aryl chlorides as feedstock for these chemical transformations, and require the use of more expensive aryl bromides and aryl iodides. The use of aryl chlorides as chemical feedstock in coupling chemistry has proven difficult but would economically benefit a number of industrial processes. The few prior art methods that can employ aryl chlorides use expensive, air-sensitive phosphine ligands. See in this connection Old et al.,
J. Am. Chem. Soc
., 1998, 120, 9722-9723, and Littke and Fu,
Angew. Chem. Int. Ed. Engl
., 1998, 37, 3387-3388, which describe phosphine-modified, palladium-mediated Suzuki coupling reactions which employ aryl chlorides as substrates. The use of a bulky phosphine (e.g. tri(tert-butyl)phosphine) or phosphine-containing moiety (e.g., di(cyclohexyl)phosphino) in ancillary ligation was shown to be fundamental in triggering the observed catalytic behavior. In addition, these phosphine ligands are often difficult to remove from the process product.
Nucleophilic N-heterocyclic carbenes, the imidazoline-2-ylidenes (sometimes commonly called imidazol-2-ylidenes) or so-called “phosphine mimics”, have attracted considerable attention as possible alternatives for the widely used phosphine ligands in homogeneous catalysis. A primary advantage of these ligands is that an excess of the ligand is not required. It appears that these ligands do not dissociate from the metal center, thus preventing aggregation of the catalyst to yield the bulk metal. Further, these imidazoline-2-ylidene carbenes also appear to be more thermally stable than phosphines.
THE INVENTION
This invention provides a catalyst system useful in many coupling reactions, such as Suzuki, Stille, Kumada, and amination reactions. A feature of this invention is the use of an imidazoline-2-ylidene, an imidazolidine-2-ylidene, a bis(imidazoline-2-ylidene), and/or a bis(imidazolidine-2-ylidene) as part of the catalyst system. These N-heterocyclic carbenes and their corresponding salts are inexpensive and readily synthesized.
A first embodiment of this invention is a composition which comprises at least one metal compound comprising at least one transition metal atom and at least one N-heterocyclic carbene or protonated salt of an N-heterocyclic carbene. The N-heterocyclic carbene is selected from the group consisting of i) an imidazoline-2-ylidene wherein the 1 and 3 positions are each, independently, substituted by an aromatic group in which each ortho position is, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such an imidazoline-2-ylidene; ii) an imidazolidine-2-ylidene wherein the 1 and 3 positions are each, independently, substituted by an aromatic group in which each ortho position is, independently, substituted by a secondary or tertiary group having at least three atoms, or a protonated salt of such an imidazolidine-2-ylidene; iii) a bis(imidazoline-2-ylidene) wherein a bridging moiety is bound to one nitrogen atom of each ring, wherein the bridge formed by the bridging moiety has at least five atoms, and wherein the remaining two nitrogen atoms are each, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such a bis(imidazoline-2-ylidene); iv) a bis(imidazolidine-2-ylidene) wherein a bridging moiety is bound to one nitrogen atom of each ring, wherein the bridge formed by the bridging moiety has at least five atoms, and wherein the remaining two nitrogen atoms are each, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such a bis(imidazolidine-2-ylidene); and mixtures of two or more of the foregoing.
Another embodiment of this invention is a novel and highly efficacious group of N-heterocyclic carbenes which have the property or characteristic of greatly enhancing the effectiveness of the foregoing catalyst systems. The N-heterocyclic carbene is selected from the group consisting of i) an imidazoline-2-ylidene wherein the 1 and 3 positions are each, independently, substituted by an aromatic group in which each ortho position is, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such an imidazoline-2-ylidene; ii) an imidazolidine-2-ylidene wherein the 1 and 3 positions are each, independently, substituted by an aromatic group in which each ortho position is, independently, substituted by a secondary or tertiary group having at least three atoms, or a protonated salt of such an imidazolidine-2-ylidene; iii) a bis(imidazoline-2-ylidene) wherein a bridging moiety is bound to one nitrogen atom of each ring, wherein the bridge formed by the bridging moiety has at least five atoms, and wherein the remaining two nitrogen atoms are each, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such a bis(imidazoline-2-ylidene); iv) a bis(imidazolidine-2-ylidene) wherein a bridging moiety is bound to one nitrogen atom of each ring, wherein the bridge formed by the bridging moiety has at least five atoms, and wherein the remaining two nitrogen atoms are each, independently, substituted by a secondary or tertiary group which has at least three atoms, or a protonated salt of such a bis(imidazolidine-2-ylidene); and mixtures of two or more of the foregoing.
Significantly better yields are obtained, often in shorter reaction times, with catalyst systems comprising the N-heterocyclic carbenes of this invention than with catalyst systems which utilize N-heterocyclic carbenes that do not have such limitations.
Further embodiments and features of this invention will be apparent from the ensuing description and appended claims.
The transition metal of the metal compound may be any of those in Groups 4-11 of the Periodic Table. For labeling of the groups of the Periodic Table, see for example, the Periodic Table appearing in
Chemical
&
Engineering News
, 1985, 69, 26. The metal compound can be in the form of an inorganic salt or an organic metal compound. Inorganic salts that can be used include the bromides, chlorides, fluorides, iodides, cyanides, nitrates, sulfides, sulfites, and sulfates. Organic metal compounds that may be used include complexes and salts such as the carboxylates, e.g., the acetates or propionates, etc. Preferred are metals from Groups 8-11, especially ruthenium, osmium, rhodium, nickel, palladium, platinum, and copper. More preferred transition metals are the Group 10 metals, particularly nickel and palladium, and especially compounds in which the formal oxidation state of nickel or palladium is zero or two. Examples of ruthenium compounds are dichloro(1,5-cyclooctadiene)ruthenium, ruthenium acetate, ruthenium iodide, and the like. Osmium compounds that can be used include osmium chloride. Suitable rhodium compounds include bis(1,5-cyclooctadiene)rhodium trifluoromethanesulfonate and rhodium chloride. Suitable copper compounds include, but are not limited to, copper chloride, copper bromide, and copper cyanide. Suitable nickel compounds include bis(1,5-cyclooctadiene)nickel, nickel acetate, nickel oxalate, nickel phosphate, nickel stearate, nickel acetylacetonate, nickel tetrafluoroborate, nickel thiocyanate, nickel carbonate, and nickel sulfamate. Examples of palladium compounds include Pd(OAc)
2
, palladium(II) chloride, Pd(CH
3
CN)
4
(BF
4
)
2
, PdCl
2
(CH
3
CN)
2
, PdCl
2
(PhCN)
2
, PdCl
2
(PPh
3
)
2
, tris(dibenzylideneacetone)dipalladium(0) [which is also referred to herein as dipalladium tris(d
Huang Jinkun
Nolan Steven P.
Trudell Mark L.
Zhang Chunming
Bell Mark L.
Hailey Patricia L.
Sieberth & Patty L.L.C.
University of New Orleans Research & Technology Foundation
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