Chemistry of hydrocarbon compounds – Alicyclic compound synthesis – From nonhydrocarbon
Reexamination Certificate
1997-05-02
2001-05-15
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Alicyclic compound synthesis
From nonhydrocarbon
C585S375000, C585S023000
Reexamination Certificate
active
06232516
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of a substituted cyclopentadiene compound, and in particular to a process that permits excellent control over the selectivity of the substitutions on the resultant substituted cyclopentadiene compound. The substituted cyclopentadiene compound has utility as, for example, a ligand of a metal or transition metal complex used to catalyze a polymerization reaction.
2. Description of the Related Art
Substituted cyclopentadienes and their derivatives have utility as, for example, ligands in metal and transition metal complexes, which complexes can be used as catalysts in a polymerization reaction. The nature of the ligands, including the substituted cyclopentadienyl ligand, on the metal complexes can have a significant affect on the efficiency of the polymerization reaction and the characteristics (for example, average molecular weight) of the polymers prepared from the process. Accordingly, a process for preparing substituted cyclopentadienes in which the selectivity of the substituted cyclopentadienes produced can be meaningfully controlled would be of great benefit.
The preparation of a substituted cyclopentadiene compound is described by Williams et al.,
J. Am. Chem. Soc.,
113, 4843-4851, (1991) (hereinafter “Williams”), the complete disclosure of which is incorporated herein by reference, which details the preparation of isopropyl substituted cyclopentadiene by the reaction of a mixture of aqueous KOH, isopropyl bromide and cyclopentadiene in a molar ratio of 40:5:1, with ADOGEN 464 being used as a phase transfer catalyst. A drawback of this process is that a mixture of tri- and tetraisopropyl cyclopentadiene in a ratio of about 35:65 is obtained. This mixture has to then undergo a separate isolation step in order to obtain the individual compounds.
From Venier et al.,
J. Am. Chem. Soc.,
112, 2808-2809, (1990) (hereinafter “Venier”), the complete disclosure of which is incorporated herein by reference, it is known to prepare di-tert-butyl cyclopentadiene with a selectivity of 90%; however, such high selectivity appears to be the exceptional case, as seen by the remaining examples set forth in Williams. The high selectivity of the preparation of di-tert-butyl cyclopentadiene is primarily due to the fact that a tertiary alkyl, with a high degree of steric hindrance, is being substituted onto the cyclopentadiene ring. In such a case it is the low probability of obtaining the tri-tert-butylcyclopentadiene compound, with its high degree of steric hindrance, which is responsible for the high percentage of di-substituted compounds.
However, a selection mechanism based on the steric effects of the substituent will not be effective in the case of substituents which have less steric hindrance, for instance n- or sec-alkyl groups.
A need therefore exists for a synthetic route to produce substituted cyclopentadiene compounds, which process allows for improved selectivity, control and flexibility over the number and kind of substituents on the cyclopentadiene ring.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process for the preparation of substituted Cp compounds with a greater selectivity and control over the substitution than the known processes. In accordance with the principles of the present invention, this and other objects are achieved in that during the reaction, the ratio of base to Cp compound is maintained in a ratio of from about 5 to about 30 mol/mol.
With the process according to the present invention, it is possible to obtain substituted Cp compounds which have various and desirable degrees of substitution, and to produce those compounds at a higher selectivity than with the known process.
Accordingly, the process according to the present invention provides synthetic routes to a wide variety of substituted Cp and substituted Cp derivatives which can be utilized in catalyst preparation, and thus fills a clear, long-felt need.
As used herein, cyclopentadiene or “Cp” can refer to either an uncharged cyclopentadiene group or its derivative, or an anionic cyclopentadienyl group or its derivative, as those skilled in the art can determine the appropriate meaning based on the context in which the term is used. Examples of cyclopentadiene derivatives include substituted cyclopentadiene groups such as methyl cyclopentadiene.
These and other objects, features, and advantages of the present invention will become apparent from the accompanying drawing which illustrates, by way of example, the principles of the present invention.
REFERENCES:
patent: 3255267 (1966-06-01), Fritz et al.
patent: 3560583 (1971-02-01), Stewart
patent: 4567308 (1986-01-01), Yoshida et al.
patent: 4814532 (1989-03-01), Yoshida et al.
patent: 4929782 (1990-05-01), Venier et al.
patent: 5144095 (1992-09-01), Venier et al.
R. Allen Williams et al., ‘Encapsulated Alkaline-Earth Metallocenes. Synthesis, Solution Behavior, and Solid-State Structures of . . . ’, Journal of the American Chemical Society, vol. 113, No. 13, Jun. 19, 1991, pp. 4843-4851.
Clifford G. Venier et al., ‘D-tert-butylcyclopentadiene and Tri-tert-butylclopentadiene’, Journal of the American Chemical Society, vol. 112, No. 7, Mar. 28, 1990.
Eckehard V. Dehmlow et al., ‘Phase Transfer Catalyzed tert-Alkylations of Cyclopentadiene and Indene: Indications of Set Processess’, Tetrahedron Letters, vol. 32, No. 41, Oct. 1991.
Green Richard
Gruter Gerardus J. M.
van Beek Johannes A. M.
DSM N.V.
Griffin Walter D.
Pillsbury & Winthrop LLP
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