Synthesis of bis (alkyl cyclopentadienyl) metallocenes

Details Synthesis of bis (alkyl cyclopentadienyl) metallocenes Synthesis of bis (alkyl cyclopentadienyl) metallocenes

1999-08-13

2001-01-16

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C585S375000, C260S66500B

Reexamination Certificate

active

06175027

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the synthesis of alkyl cyclopentadienes and to the conversion thereof to bis(alkyl cyclopentadienyl) metallocenes.
BACKGROUND OF THE INVENTION
It is known to produce bis(n-alkyl cyclopentadienyl) metallocenes by reaction of alkyl cyclopentadienyl lithenides with Group IV metal tetrahalides.
It is also known to react a cyclopentadienyl Grignard in ether with allyl bromide or tert.butyl bromide. See, e.g.,
Metallocenes,
Wiley-VCH, Vol. 1, 469-47 (1998), citing Riemschneider, R. Z.,
Naturforsch
. (1963) 18:641-645.
SUMMARY OF THE INVENTION
Pursuant to this invention, a cyclopentadienyl or a substituted cyclopentadienyl Grignard synthesized in tetrahydrofuran (THF) is added to a refluxing THF solution of an n-alkyl halide. The reaction is quenched with aqueous lower fatty acid, preferably acetic acid, to produce a reaction mixture from which an n-alkylated cyclopentadiene may be separated in good yield, e.g., 70% to 80%. The n-alkylated cyclopentadiene may be converted through an alkali metallide to a Group IV metallocene in a 60% to 70% yield.
Alkyl halides useful in this invention are selected to provide the desired alkyl substituted cyclopentadiene. Preferably, alkyl halides of the formula RX, in which R equals C
1
to C
6
alkyl and X is a halogen, are used. All substituted cyclopentadienes which may be converted to Grignard compounds are useful in the invention. Cyclopentadienes having one to four ring positions substituted by alkyl groups are appropriate.
DETAILED DESCRIPTION OF THE INVENTION
General Description of Cyclopentdienyl Grignard Synthesis
Syntheses of cyclopentadienyl Grignard reagents are described in
Ann. Chem.
(1915) 4:56, 71,
Compt. Rend.
(1914) 158:1963, and Riemschneider, R. Z.,
Naturforsch.
(1963) 18:641-645.
In the preferred practice of this invention, dicyclopentadiene is cracked, e.g., by the method described in U.S. Pat. No. 5,877,366 (Birmingham), to provide cyclopentadiene monomer which is diluted into THF and then passed at THF reflux temperature into a 2 to 4 M, preferably 3 M THF, solution of an alkyl magnesium halide, RMgX, in which R and X are as defined, preferably methyl magnesium chloride. The reaction mixture is agitated under reflux. Unreacted cyclopentadiene is moved by distillation to provide a residual solution of cyclopentadiene Grignard (CpMgX) in THF. The THF concentration in the residual solution may be adjusted to 1 M.


REFERENCES:
patent: 5474716 (1995-12-01), Lisowsky
patent: 5831106 (1998-11-01), Langhauser et al.
patent: 5877366 (1999-03-01), Birmingham
Reimschneider, Von R., Zeitschrift Fur Naturforschung, vol. 18b, No. 8, pp. 641-645, Aug. 1963.

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