Chemistry of hydrocarbon compounds – Alicyclic compound synthesis – By alkylation or alkyl transfer
Patent
1999-03-03
2000-10-24
Knode, Marian C.
Chemistry of hydrocarbon compounds
Alicyclic compound synthesis
By alkylation or alkyl transfer
585 1, 585350, 585671, 568 8, 568 77, 568667, 564460, 564454, 564464, 502155, 502103, 502113, 502117, 526160, 526161, 526172, C07C 202, C07C 720, C07C 522, C07C 527, C07F 902
Patent
active
061370193
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for converting a geminally substituted cyclopentadiene containing 2-6 substituents into a non-geminally substituted cyclopentadiene.
2. Description of Related Art
Cyclopentadiene compounds, both substituted and unsubstituted, are used widely as a starting material for preparing ligands in metal complexes having catalytic activity. As metals in these complexes use is made in particular of transition metals and lanthanides.
A geminally substituted cyclopentadiene is a cyclopentadiene containing two substituents, which are not identical to a hydrogen atom, on the sp.sup.3 carbon atom of the cyclopentadiene ring. These geminally substituted cyclopentadienes have the drawback that they cannot be converted into an aromatic anion by deprotonation. As a consequence, geminally substituted cyclopentadienes cannot be used as anionic ligand in the synthesis of metallocene catalysts.
Since direct alkylation of cyclopentadiene compounds is usually attended by geminal substitution (see Jutzi, Synthesis 1993, 684), there is a need for a process for converting a geminally substituted cyclopentadiene into a non-geminally substituted cyclopentadiene.
BRIEF DESCRIPTION OF THE INVENTION
It is the aim of the invention to provide this process.
The invention is characterized in that the geminally substituted cyclopentadiene is reacted with a base, sodium or potassium at a temperature of 0-200.degree. C.
This ensures that the geminally substituted cyclopentadiene is converted into a non-geminally substituted cyclopentadiene.
For converting a geminally substituted cyclopentadiene into a non-geminally substituted cyclopentadiene, one of the substituents on the sp.sup.3 carbon atom is to be removed or shifted (alkyl shift).
The process according to the invention provides a method for removing a substituent from the sp.sup.3 carbon atom. For this, a C--C bond must be broken. Although C--H bond breakage is no exception during an organic synthesis, C--C bond breakage is very rare. Most of the examples of state of the art C--C bond breakage relate to C--C bond breakage in strained alkanes.
The geminally substituted cyclopentadiene may contain 2-6 substituents. At least two substituents should be present on the sp.sup.3 carbon atom of the cyclopentadiene ring.
Preferably the geminally substituted cyclopentadiene contains 6 substituents.
Suitable substituents which can be split off via the process according to the invention are, for example, alkyl groups, linear as well as branched ones, and cyclic and aralkyl groups.
The methyl group is not suitable as substituent to be split off.
Besides carbon and hydrogen, the substituents may also comprise one or more hetero atoms from groups 14-17 of the Periodic System, for example O, N, Si or F. Examples of suitable groups are ethyl,(iso)propyl, secondary butyl, secondary pentyl, secondary hexyl and secondary octyl, (tertiary) butyl and higher homologues, cyclohexyl and 2-phenylethyl. Examples of substituents with hetero atoms from groups 15 and 16 of the Periodic System of the Elements are substituents according to the formula (R'.sub.n D--R--), where Elements, and
The R group forms the link between the Cp and the DR'.sub.n group.
The R' groups may each, separately, be a hydrocarbon radical containing 1-20 carbon atoms (such as alkyl, aryl, aralkyl, and the like). Examples of such hydrocarbon radicals are methyl, ethyl, propyl, butyl, hexyl, decyl, phenyl, benzyl, and p-tolyl. R' may also be a substituent which, in addition to or instead of carbon and/or hydrogen, contains one or more hetero atoms from groups 14-16 of the Periodic System of the Elements. Thus a substituent may be an N-, O-, and/or Si-containing group.
The R group may be a hydrocarbon group containing 1-20 carbon atoms (such as alkylidene, arylidene, arylalkylidene and the like). Examples of such groups are methylene, ethylene, propylene, butylene, phenylene, with or without a substituted side chain. Preferably, the R group has the followin
REFERENCES:
patent: 5648578 (1997-07-01), Layman et al.
Jutzi, et al., "Dimethylaminoalkyl and Methoxyalkyl Substituted Tetramethylcyclopentadienes: Synthesis of Novel PolydentateLigands," Systhesis, No. 7 (Jul. 1993), 684-686.
Gruter Gerardus J. M.
van Beek Johannes A. M.
Dang Thuan D.
DSM N.V.
Knode Marian C.
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