Synthesis of 4-ketocyclopentene compounds

Details Synthesis of 4-ketocyclopentene compounds Synthesis of 4-ketocyclopentene compounds

1999-11-19

2001-10-30

Padmanabhan, Sreeni (Department: 1713)

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

Organic compounds

Oxygen containing

C568S346000

Reexamination Certificate

active

06310256

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the synthesis of 4-ketocyclopentene compounds including further substituted derivatives thereof, and their conversion to cyclopentadiene compounds or substituted cyclopentadiene compounds, which are useful chemicals, particularly in the synthesis of cyclopentadienyl containing metal complexes useful in addition polymerization catalyst compositions. Group 4 metal complexes containing the foregoing cyclopentadienyl ligands are especially suited for use in catalyst compositions for the homopolymerization of ethylene or propylene and the copolymerization of ethylene with an &agr;-olefin. The present process is particularly suitable for use in the industrial scale preparation of 4-ketocyclopentene or substituted 4-ketocyclopentene compounds, cyclopentadiene or substituted cyclopentadiene derivatives thereof, and in the synthesis of cyclopentadienyl or substituted cyclopentadienyl containing metal complexes therefrom.
BACKGROUND
The preparation of cyclopentadiene compounds from various starting materials is well known. Metal complexes containing cyclopentadienyl or substituted cyclopentadienyl ligands are also well known. Several techniques for preparing such ligands are disclosed in U.S. Pat. No. 5,703,187, 4,985,576, 5,646,083, 5,597,935, and EP-A-563365. In copending application Ser. No. 08/122958, filed Jul. 27, 1998, the preparation of certain 1 H-cyclopenta(/)ophenanthrene containing metal complexes and their use in addition polymerization catalyst compositions is disclosed and claimed. The technique for preparing such complexes disclosed by the reference started with 1H-cyclopenta-(I)phenanthrene. In
JACS,
78, 2547-2551 (1956), a synthetic scheme for preparing 1H-cyclopenta(I)phenanthrene, the ultimate step involving dehydration of 2,3-dihydro-2-oxo-1H-cyclopenta(I)phenanthrene with boric acid was disclosed. Disadvantageously, this particular procedure resulted in low yields and insufficient purity of the resulting ligand group containing compounds.
Previously known synthetic procedures involved multiple unit operations, thereby making the process less efficient than desired. Accordingly, it would be desirable if there were provided a process for preparing 4-ketocyclopentene or substituted 4-ketocyclopentene compounds and cyclopentadiene or substituted cyclopentadiene derivatives thereof in higher yields and purity.
SUMMARY OF THE INVENTION
According to the present invention there is provided a process for forming 4-ketocyclopentene and substituted 4-ketocyclopentene compounds starting from the corresponding 1-carbohydrocarbyloxy-2-keto-4-hydroxy-5-cyclopentene by reduction followed by decarboxylation. Preferably, the reduction is occasioned by reaction of the initial compound with a metal, preferably zinc. The decarboxylation is preferably conducted by further reaction of the intermediate with an inorganic halide compound and one or more organic acids under hydrolysis and condensation conditions. The reduction and decarboxylation may be conducted simultaneously or sequentially in the same reactor or in different reactors. Preferably the carboxylate compound is contacted with zinc in the presence of a mixture of an organic acid and hydrochloric acid.
The foregoing procedure is illustrated schematically as follows:
wherein, R is C
1-20
hydrocarbyl, preferably C
1-4
alkyl; and
R
1
independently each occurrence is hydrogen, hydrocarbyl, silyl, germyl, halide, or halo- substituted hydrocarbyl, said R
1
group having up to 40 atoms not counting hydrogen atoms, and optionally two or more of the foregoing adjacent R
1
groups may together form a divalent derivative thereby forming a saturated or unsaturated fused ring or multiple ring system, and further optionally one or more of the carbons of R
1
in any of the so formed rings may be replaced by a nitrogen, boron, phosphorus or sulfur atom.
Beneficially, the foregoing improved process incorporates multiple chemical transformations into a single step process thereby significantly improving the efficiency of the preparation.
In a further embodiment of the present invention the resulting ketone is converted to a cyclopententadiene or substituted cyclopentadiene compound by a series of reactions which beneficially may be performed sequentially in the same reactor or in multiple reactors. In the process the ketone is reduced to form an intermediate alcohol, the hydroxyl functionality is replaced under substitution conditions with a leaving group or otherwise converted to a leaving group, and the resulting product is deprotonated under base induced elimination conditions to form the cyclopentadiene compound. If desired, a suitable functional substituent may be incorporated simultaneously with the elimination step. This process is illustrated schematically as follows:
wherein R
1
is as previously defined, and
Lg is a suitable ligand group that is subject to base induced elimination. Preferred Lg groups are: halo, silyl, OSO
2
R
6
, —Si(R
5
)
2
—, —Si(R
5
)
2
N(R
5
)
2
), or —Si(R
5
)
2
N(R
5
)— groups, wherein R
5
is a C
1-20
aliphatic or cycloaliphatic group, and R
6
is R
5
or a C
6-20
aryl group or sulfonate ester such as tosyl or mesyl. Most preferably, Lg is halo, especially bromo.
When further cyclopentadienyl substituted compounds are desired, the final elimination step may be followed by further substitution of Lg with a functional substituent or even formation of dimeric bridged ligands through a coupling of ligand groups, utilizing techniques well known to the skilled artisan. Highly preferred functional substituents include metals, hydrocarbyl, silyl, hydrocarbyl- or polyhydrocarbyl- substituted silyl, silyl- or polysilyl- substituted hydrocarbyl groups, metallated derivatives of such hydrocarbyl, silyl, substituted silyl or subsitituted hydrocarbyl groups, or bridging groups of the formula: —Z′Y— when a coupled product is formed, or masked, metallated, or coupled derivatives thereof, said functional substituent having up to 50 atoms not counting hydrogen, wherein:
Z′ is SiR
5
2
, CR
5
2
, SiR
5
2
SiR
5
2
, CR
5
2
CR
5
2
, CR
5
═CR
5
, CR
5
2
SiR
5
2
, BR
5
, B═NR
5
2
, or GeR
5
2
; and
R
5
each occurrence is independently hydrogen, or a member selected from hydrocarbyl, hydrocarbyloxy, silyl, halogenated alkyl, halogenated aryl, and combinations thereof, said R
5
having up to 20 non-hydrogen atoms, and optionally, two R
5
groups from Z′ (when R
5
is not hydrogen), or an R
5
group from Z′ and an R
5
group from Y form a ring system.
Masked derivatives of the foregoing ligands are those ligands containing an easily removable group at the position desired for later coupling or further functionalization of the compound. An example is a trihydrocarbylsilyl group, especially trimethylsilyl. In a highly preferred embodiment of the invention the foregoing Lg group is replaced with the desired functional ligand group in a single step which is a combination of elimination, deprotonation and replacement operations using two equivalents of base for each equivalent of cyclopentediene compound and the addition of the source for the functional group, R
7
Fs, where R
7
is a leaving group, preferably halogen or a sulfonate ester, and Fs is a functional substituent, preferably —Z′YH. Because the combination of three processes in one step does not involve dehydration of an alcohol intermediate, formation of dimeric byproducts through a Diels-Alder reaction of the diene is avoided. This combined process may be illustrated schematically as follows:
Finally according to the present invention there is provided a process for preparing metal complexes comprising cyclopentadienyl- or substituted cyclopentadienyl- ligands using one or all of the foregoing intermediate process steps. The present processes result in the highly efficient production of metal complexes and metal complex intermediates.
DETAILED DESCRIPTION OF THE INVENTION
All reference to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, pu

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