Chemistry of hydrocarbon compounds – Alicyclic compound synthesis – Polycyclic product
Reexamination Certificate
2001-02-22
2002-07-02
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Alicyclic compound synthesis
Polycyclic product
C585S359000, C585S431000, C585S438000, C585S469000
Reexamination Certificate
active
06414206
ABSTRACT:
This application claims priority from European Patent Application No. 00200628.6, filed Feb. 23, 2000.
The present invention relates to a process for preparing bisindenylalkanes, in particular bisindenylethane and analogues thereof.
Bisindenylethane, i.e. 1,2-bis(3-indenyl)ethane, is an intermediate in the synthesis of metallocene catalysts which typically are used in combination with a co-catalyst such as methylaluminoxane for the isospecific (co)polymerization of ethylenically unsaturated monomers, e.g., the production of isotactic polypropylene.
Several processes for preparing bisindenylethane and analogues thereof are known in the art.
J. Organometallic Chemistry,
342 (1988) 21-29, to S. Collins et al. discloses a process for preparing 1,2-bis(3-indenyl)ethane from 1,2-dibromoethane wherein two (see page 22, Scheme 1) or less than two equivalents (see page 27, Example 1) of indenyllithium are used. The reaction was carried out in solution in THF/HMPA and by slowly warming the reaction mixture from −78° C. to room temperature and gave the desired end-product in 65% yield after crystallization from acetone and ethanol.
J. Am. Chem. Soc.,
109 (1987) 6544-6545, to J. A. Ewen et al. discloses a process similar to the one of Collins wherein, as described in the supplementary material to the article, two equivalents of indenyllithium are reacted with 1,2-dibromoethane dissolved in THF by warming the reaction mixture from −91° C. to 25° C. and stirring for 4 h. Bisindenylethane was obtained in a crude yield of 60%. The product was recrystallized from ethanol.
EP-A-0 485 823 to Hoechst discloses a process similar to that of Collins, but with the modification that the reaction is performed in a solution of just THF. Bis(2-methyl-indenyl)ethane was obtained after warming the reaction mixture from −78° C. to room temperature and stirring for 5 h in 49% yield after chromatographic purification (see page 9, Example III).
EP-A-0 575 875 to Spherilene discloses a process similar to the Hoechst one; however, the reaction mixture is warmed from −78° C. to 50° C. and the reaction mixture is stirred for 12 h. A yield of 51.6% of unpurified bisindenylethane was obtained (see page 8, lines 44-57). A yield of 48% of crude product was obtained when 4,7-dimethylindene was one of the starting materials (see page 9, line 53, through page 10, line 4).
Organometallics,
10 (1991) 1501-1505, to Grossman et al. discloses the preparation of 1,2-bis(3-indenyl)ethane on page 1502 (left column) in a yield of 54% (crude) by reacting indenyllithium with 1,2-dibromoethane in a molar ratio of 2.2:1 at −78° C., warming the solution to room temperature, and stirring for several hours at this temperature.
As an alternative to the homogeneous processes described above, EP-A-0 574 597 to Hoechst discloses the preparation of bisindenyl compounds of a formula III via a heterogeneous reaction (i.e. suspension) in an aliphatic or aromatic hydrocarbon. The reaction scheme on page 4 of this document gives a general description of the synthesis of bisindenyl compounds (the preparation of bisindenylethane is neither described nor exemplified in this document). The reaction conditions are mentioned on page 8 of this document. In particular, it is mentioned in line 48 of page 8 that the reaction temperature preferably is from 0 to 120° C. and in line 53 that the molar ratio of metallated indene to inter alia dibromoalkyl compound preferably is 2:1.
These prior art processes have the disadvantage that the yields are low (we found that the main by-product is spiro-indene in the case of bisindenylethane) and that as a result thereof the bisindenylalkane needs to be purified—in particular, chromatographic purification is undesired when the reaction is carried out on an industrial scale—before further reaction (toward a metallocene catalyst) can take place. In some cases, the reaction times are unacceptably long as well. We have found a new process which does not suffer from these drawbacks.
According to the present invention, a process is provided for preparing bisindenylalkanes of formula I:
wherein R
1
, R
2
, R
3
, and R
4
independently represent H or a C
1
-C
6
hydrocarbon group or R
1
and R
2
or R
1
and R
3
or R
3
and R
4
together with the carbon atoms to which they are attached form a saturated or unsaturated 5- or 6-membered ring, said ring being optionally substituted with a C
1
-C
4
hydrocarbon group, and R
5
represents a C
1
-C
6
hydrocarbon group, comprising reacting, at a temperature which does not exceed about 5° C., a metallated indene of formula II with a disubstituted hydrocarbon of formula III:
wherein R
1
, R
2
, R
3
, R
4
, and R
5
have the same meaning as defined above, M represents a metal ion, and X independently represents a suitable leaving group, in a suitable reaction medium wherein the molar ratio of II to III is 2.05 or higher.
Hence, the molar ratio of II to III is 2.05:1 or higher. Preferably, the molar ratio of metallated indene (II) to disubstituted hydrocarbon (III) is 2.1 or higher, more preferably 2.2 or higher, most preferably 2.2 to 3.0.
At temperatures above about 5° C. by-products are being formed at an undesirable level. Hence, preferably the reaction temperature does not exceed about 0° C.
It was found that when using a reaction temperature and a molar ratio of metallated indene to disubstituted hydrocarbon as presently claimed, the product selectivity, reaction time and/or yield improved considerably over the values described in the prior art.
R
1
, R
2
, R
3
, and R
4
independently represent H or a C
1
-C
6
hydrocarbon group or R
1
and R
2
or R
1
and R
3
or R
3
and R
4
together with the carbon atoms to which they are attached form a saturated or unsaturated 5- or 6-membered ring, said ring being optionally substituted with a C
1
-C
4
hydrocarbon group. It is noted that in the case that R
3
and R
4
together with the carbon atoms to which they are attached form an aromatic ring, the double bond in the five-membered ring in the compound of formula I and II will shift to the position of the carbon atoms to which R
3
and R
4
are attached as, for example, when fluorene is used as a starting material (see below). Preferably, R
1
, R
2
, R
3
, and R
4
independently represent H or a CH
3
(i.e. methyl) group, most preferably H.
Typical examples of indenes from which the metallated indene of formula II can be prepared include indene, 2-methylindene, 2-methylbenzoindene, 4,7-dimethylindene, and fluorene. These starting materials are either commercially available or can be prepared by methods known to a person skilled in this art, e.g., see page 8, lines 11-36, of EP-A-0 574 597 cited above.
R
5
represents a C
1
-C
6
hydrocarbon group. It may be a linear or branched, divalent hydrocarbon group. Preferably, it represents a linear C
2
-C
4
hydrocarbon group. Most preferably, it represents an ethylene group.
M represents a metal ion. Suitable metal ions include alkali and alkaline-earth metal ions such as Li, Na, K, and Mg. Most preferably, M represents a Li ion.
X independently represents a suitable leaving group. Such groups are known to a person skilled in this art, for example, the ones discussed on pages 352-357 of J. March,
Advanced Organic Chemistry,
Fourth Edition, John Wiley & Sons, New York, 1992. Suitable leaving groups include halogen atoms and mesylate, tosylate, and triflate groups. Preferably, the leaving group is a halogen atom such as a Br or Cl atom. More preferably, X represents a Br atom. Most preferably, each X represents a halogen atom, in particular a Br atom.
A typical example of a compound according to formula III is 1,2-dibromoethane. Compounds of formula III are either commercially available or can be prepared by methods known per se in the art.
The metallated indene of formula II is prepared according to procedures known to a skilled person. Suitable metallating agents or bases are known and are described, for example, in J. March,
Advanced Organic Chemistry,
Fourth Edition, pages 606-609. Typical examples in
Kalmoua Faysal
Woudenberg Richard Herman
Akzo Nobel NV
Dang Thuan D.
Fennelly Richard P.
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