WO1997042143A1

WO1997042143A1 - Process for the preparation of a spiro[2.4]-hepta-4,6-diene

Info

Publication number: WO1997042143A1
Application number: PCT/NL1997/000195
Authority: WO
Inventors: Gerardus Johannes Maria Gruter; Johannes Antonius Maria Van Beek; Henricus Johannes Arts
Original assignee: Dsm N.V.
Priority date: 1996-05-03
Filing date: 1997-04-16
Publication date: 1997-11-13
Also published as: AU2310797A; NL1003001C2

Abstract

The invention relates to a process for the preparation of a spiro[2.4]-hepta-4,6-diene (SHD). The invention is charaterised in that use is made of an at least mono-ring-substituted β-haloethylcyclopentadiene, which is converted into the corresponding SHD under the influence of a base. The invention also relates to SHD obtainable by means of said process.

Description

PROCESS FOR THE PREPARATION OF A SPIROr2.41-HEPTA-4, 6-DIENE

The invention relates to a process for the preparation of a spiro[2.4]hepta-4,6-diene.

Spirof2.4]hepta-4, 6-dienes (hereafter also referred to as SHD) and a process for their preparation are described by L.G. Menchikov et al. in Russian Chemical Reviews, 63,6), 449-69 (1994).

Said reference gives a number of routes for the preparation of SHDs of the following structural formula:

in which the carbon atoms, numbered from 1 to 6, may be either substituted or unsubstituted. Three major routes are indicated: a) starting from diazocyclopentadiene. This route is said to have a low yield and a low selectivity, while it involves a complex process and explosive raw materials; b) through cyclomethylenation of the exocyclic double bond in fulvenes. This route, too, is rather complex and can be carried out with only very few carbenes since only nucleophilic carbenes are suitable for the reaction as meant; the route may give rise to various side reactions; c) through cycloalkylation of cyclopentadiene using 1,2-dibromomethane. This method, which is described for the unsubstituted cyclopentadiene and which yields the desired SHD with a low selectivity when use is made of mono- or poly- substituted cyclopentadiene. Additional drawbacks are the use of low reaction temperatures (the article referred to mentions a temperature of - 70°C) as well as the use of liquid ammonia as solvent.

Thus, there is a need for a process for the preparation of an SHD with at least mono-substitution on the cyclopentadienyl ring which does not, or to a much lesser degree, entail the above-mentioned problems.

The process is characterised in that an at least mono-ring-substituted β-haloethyl-cyclopentadiene is converted into the corresponding substituted SHD under the influence of a base. This results in simple formation of the SHD with a high selectivity.

As starting product for the process according to the invention use is made of an at least mono-ring- substituted β-haloethylcyclopentadiene of the following formula:

where R and R₄-R₇ may be hydrogen, or an alkyl, aryl or aralkyl group, subject to the condition that at least one of the R₄-R₇ groups is not hydrogen (if R,-R₇ = H, a non-ring-substituted cyclopentadienyl ring is present). The process is also suitable for the preparation of SHDs on the basis of compounds according to formula II, in which substituents on the cyclopenta¬ dienyl ring form part of a ring system. This is found in compounds: a) based on indene, by which compounds of the following formula are meant:

b) based on tetrahydroindene, by which compounds of the following formula are meant:

H

/

H R \ (lib)

C R

I \ /

R C - Hal

R c) the fluorene derivatives of II, including

and

In these as well as in other ring system containing SHD derivatives the C atoms that form part of the cyclopentadienyl, aryl or cyclohexyl ring may also be substituted, with similar groups as mentioned above for compounds of formula II.

The cyclopentadiene compound may also be a heterocyclopentadiene. Here and hereinafter the term heterocyclopentadiene refers to a compound which is derived from cyclopentadiene but in which at least one of the C atoms in the 5-ring has been replaced by a hetero atom, the hetero atom having been selected from group 14, 15 or 16 of the Periodic System of the Elements. If more than one hetero atom is present in the 5-ring, these hetero atoms can be either the same or different. More preferably, the hetero atom is selected from group 15, and still more preferably the hetero atom is phosphorus.

The process according to the invention is carried out under the influence of a base, which is understood to be a compound capable of abstracting hydrogen (H) (as indicated in formula II). As base, use may be made, for example, of organolithium compounds (RLi) or organo-magnesium compounds (RMgX) , where R = an alkyl, aryl or aralkyl group and X = halide, such as, for example, n-butyllithium or isopropylmagnesium chloride. Potassium hydride, sodium hydride, inorganic bases (such as NaOH and KOH) , and alcoholates of Li, K and Na can also be used as base. Metallic Na and K are also suitable. Mixtures of the above-mentioned compounds can also be used. In particular the use of a Li-alkyl compound, and even more preferably the use of n-butyl lithium, leads to a high SHD yield.

Besides the at least mono-substitution of the cyclopentadienyl ring which is necessary according to the invention (substituents R₄-R₇), also the spiro ring (or the cyclopropane ring) in formula I may be substituted, the substituents being the R-groups indicated in formula II, which may be the same or different. Any sterical hindrance between the substituted cyclopentadienyl ring and the substituted cyclopropane ring will determine the effectivity of the process according to the invention.

The process is also suitable in the preparation of poly-ring-substituted SHDs, in particular of bi-, tri- and tetracyclopentadienyl-ring- substituted SHDs. In the method that is suitable for this according to the invention use is made of compounds according to formula II, with at least two, three and, respectively, at least four of the groups R₄-R₇ not being hydrogen. Preferably these 2, 3 and, respectively, 4 substituents are alkyl groups, chosen from the group formed by methyl, ethyl, propyl, isopropyl or phenyl.

In the process according to the invention it is advantageous for the -Hal group in formula (II) to be a Cl group; this gives a high selectivity to the SHD.

One way of obtaining compound (II) is to alkylate the corresponding, at least mono-substituted cyclopentadiene. Such a process is described by P.

Jutzi et al . in Synthesis, July '93, pp. 684-6. There, after first being converted into the anion with n- butyllithium, a tetramethylcyclopentadiene is alkylated with 2-chloro-l-N,N-dimethylamino ethane or with 2- chloro-l-(p-toluenesulphonyl )ethane. A problem encountered in such an alkylation is that only geminal alkylation takes place. The geminally alkylated products cannot be converted into an SHD.

To preferentially achieve non-geminal alkylation, the alkylation is carried out under the influence of a Lewis base whose conjugated acid has a dissociation constant for which pK_a < -2.5.

Such a process yields a substituted cyclo¬ pentadiene in which the carbon atoms of the cyclopenta¬ diene ring, which are substituted, are mainly only mono-substituted (or, in other words: the number of substituted C atoms of the cyclopentadiene increases by 1 as a result of the alkylation, whereas, in a geminal substitution, the number of substituted C atoms remains the same) .

The process is therefore suitable for the alkylation of a cyclopentadiene which is at least mono- substituted (in the case of unsubstituted cyclopenta¬ diene, no geminal addition can and will occur); the maximum number of C atoms in the cyclopentadiene substituted before the alkylation is carried out is, on the other hand, 4 (in the case of a cyclopentadiene which is substituted at all 5 C atoms of the ring, only geminal substitution can take place).

Preferably, the process is carried out under the influence of one or more weak Lewis bases whose conjugated acid has a pK_a of - 2.5 to -15, more preferably of -2.5 to -10. Ethers may be mentioned as an example of suitable weak Lewis bases. Particularly suitable are: dimethoxyethane (pK_a = -2.97), ethoxyethane (pK_a = -3.59), isopropoxyisopropane (pK_a = -4.30), methoxymethane (pK_a = -3.83), n-propoxy- n-propane (pK_a = -4.40), n-butoxy-n-butane (pK_a = -5.40), ethoxy-n-butane (pK_a = -4.12), methoxybenzene (pK_a = -6.54), dioxane (pK_a = -2.92).

The starting point in this alkylation is the anion of the relevant cyclopentadiene. In order to obtain said anion, H abstraction should take place. This is a procedure known per se for which use can be made of a Bronsted base. Suitable for this purpose are hydroxide (such as NaOH, KOH) , hydrides (such as KH) , alkylalkali-metal compounds (such as the Li-alkyls, for example n-butyllithium). In this connection, the reaction temperature is not critical, room temperature already being suitable for the purpose.

The alkylation reaction is carried out with an alkylating agent. Any compound which can attach a -CH₂-CH₂-HAL group to the at least mono-substituted cyclopentadiene is in principle suitable for this purpose. In particular, organohalides and organosulphonyl compounds are suitable for this purpose. A particularly suitable organosulphonyl alkylhalide, because of its reactivity, is the 2-halo- 1 (p-toluenesulphonic acid)ethylene having the following structural formula:

H. C-/QVs-0-CH₂-CH₂-HAL

where:

HAL = halide

Alkylation with Cl as HAL group is also preferred. Such a preferred embodiment increases the selectivity to the SHD to be obtained.

The process according to the invention is usually carried out in a solvent. Any compound or mixture of compounds in which (I) and (II) are soluble is suitable. Preferably, as solvent a compound is used which exhibits a Lewis base character . This promotes H abstraction by the base. Particularly suitable are ethers, both weak Lewis base ethers (a base whose conjugated acid has a pKa value < -2.5, such as dimethoxyethane, diethylether and dioxane), and, which is preferred, strong Lewis base ethers (such as tetrahydrofuran (THF) with a corresponding pKa value of -2.0. The process according to the invention is usually carried out at a temperature above -15°C. Room temperature or a slightly higher temperature (i.e. a temperature of 15-50°C) is already highly suitable for carrying out the process. The pressure does not have any significant effect, so that the preparation can be carried out already at atmospheric pressure. Of course the presence of interfering components having an adverse effect on the selectivity (such as oxygen, carbon dioxide, water) should be prevented. The SHDs that can be prepared by the process according to the invention are suitable for many applications. Some of these are indicated in the article in Russian Chemical Reviews referred to: SHDs are suitable for the preparation of herbicides, insecticides, medicinal preparations and colourants. Page 458 ff. of the article referred to describes a large number of chemical conversions of the SHDs.

Through simultaneous decyclisation of and substitution on the cyclopropane ring it is possible to prepare functionalised, substituted cyclopentadienyl compounds, which can serve as the raw material for the preparation of complexes with transition metals such as the functionalised ferrocenes, titanocenes and others. In principle, complexing can be carried out with any transition metal from groups 3-10 of the Periodic System of the Elements.

In particular, such functionalised, substituted cyclopentadienyl compounds are suitable for use as a ligand for metallocene compounds which in turn are extremely suitable for use as a catalyst in olefin polymerisations.

The polymerisation of α-olefins, for example ethylene, propylene, butene, hexene, octene and mixtures thereof and with dienes, can be carried out in the presence of the metal complexes with the cyclo¬ pentadienyl compounds according to the invention as ligand. Said polymerisations can be carried out in the manner known for the purpose and the use of the metal complexes as catalyst component does not necessitate any essential adaptation of these processes. The known polymerisations are carried out in suspension, solution, emulsion, gas phase or as bulk polymerisation. An organometallic compound is normally used as co-catalyst, the metal being chosen from groups 1, 2, 12 or 13 of the Periodic System of the Elements. Mention may be made, for example, of trialkylaluminium, alkylaluminium halides, alkylaluminoxanes (such as methylaluminoxanes) , tris(pentafluorophenyl)borate, dimethylaniliniumtetra(pentafluorophenyl)borate or mixtures thereof. The polymerisations are carried out at temperatures between -50°C and +350°C, more particularly between 25 and 250°C. The pressures used are generally between atmospheric pressure and 250 MPa, for bulk polymerisations more particularly between 50 and 250 MPa, and for the other polymerisation processes between 0.5 and 25 MPa. As dispersants and solvents, use may be made of, for example, hydrocarbons, such as pentane, heptane and mixtures thereof. Aromatic, optionally perfluorinated, hydrocarbons are also suitable. The monomer to be used in the polymerisation may also be used as dispersant or solvent. The invention will be explained in greater detail by reference to the following examples and comparative experiments, without these implying any restriction of the invention. Characterization of the products obtained involved the following analytical methods.

Gas chromatography (GC) was carried out on a Hewlett-Packard 5890 series II with an HP crosslinked 5

- 10 -

methyl silicon gum (25 m x 0.32 mm x 1.05 μm) column. Combined gas chromatography/ mass spectrometry (GC-MS) was carried out with a Fisons MD800 equipped with a quadrupole mass detector, autoinjector Fisons AS800 and CPSilδ column (30 m x 0.25 mm x 1 μm, low bleed). NMR was carried out on a Bruker ACP200 (¹H=200 MHz; ¹³C=50 MHz) or Bruker ARX400 (¹H=400 MHz; ¹³C=100 MHz). To characterize metal complexes of a Kratos MS80 or alter¬ natively a Finnigan Mat 4610 mass spectrometer was used.

Example I

The synthesis of 1,2 ,3,4-tetramethyl-5-(2-chloroethyl )- cyclopentadiene A 1 litre three-necked flask provided with a dropping funnel, condenser, mechanical stirrer and nitrogen inlet was filled with 30.5 g of 1,2,3,4- tetramethylcyclopentadiene (0.25 mol), dissolved in 700 ml of ethoxyethane, and cooled to 2°C. Then 160 ml of n-butyllithium (1.6 M in hexane; 0.26 mol) was added dropwise in the course of 2 hours. Stirring was then carried out for 18 hours at room temperature with the aid of a mechanical stirrer. After that, 36.0 g of 1- bromo-2-chloroethane (0.25 mol) was added in one operation. The reaction mixture was stirred for 10 days at room temperature. From GC analysis of a sample, the conversion of the tetramethylcyclopentadiene was found to be 91%. To the reaction mixture, 100 ml of water was added, after which the aqueous phase and the organic phase were separated. The organic layer was washed once with 50 ml of saturated aqueous sodium chloride solution, dried (with sodium sulphate), filtered and evaporated down. The residue (43.9 g) was found from GC analysis to have the following composition: in addition to the original substances l-bromo-2-chloroethane (9% by weight) and 1,2,3, 4-tetramethylcyclopentadiene (9% by weight), only non-geminally coupled product (84%) and geminally coupled product (16%) were found to be present.

Example II The product obtained in Example I (43.9 g), which was found from GC analysis to contain about 32 g of 1,2,3,4-tetramethyl-5(2-chloroethyl)cyclopentadiene (0.175 mol), was dissolved in 300 ml of THF. The solution was cooled to -60°C, after which 115 ml of n- butyllithium (1.6 M in hexane; 0.184 mol) was added dropwise. The reaction mixture was brought to room temperature, after which it was stirred for 40 hours. The THF was evaporated off and the residue taken up in 200 ml of ethoxyethane. 100 ml of water was added, after which the water phase and the organic phase were separated. The organic phase was washed once with 100 ml of water. The combined water layer was extracted once with ethoxyethane. The combined organic layer was washed once with 50 ml of saturated sodium chloride solution, dried (sodium sulphate), filtered and evaporated down. The residue (43.2 g) was a pale yellow liquid, which was purified by means of column chromatography (silica gel, petroleum ether as mobile solvent). By means of ^λH NMR and GC-MS the yield, 24.2 g of colourless liquid, was characterised as being 4,5,6,7-tetramethyl-spiro[2,4]-hepta-4,6-diene. The efficiency was 93%, based on the amount of 1,2,3,4- tetramethyl-5-(2-chloroethyl)cyclopentadiene started from, and 65% based on 1,2,3,4-tetramethylcyclo- pentadiene.

Claims

C L A I M S

1. Process for the preparation of a spiro[2.4]hepta- 4,6-diene (SHD), characterised in that an at least mono-ring-substituted β-haloethylcyclopentadiene is converted into the corresponding SHD under the influence of a base.

2. Process according to claim 1, characterised in that as base an organometallic compound is used.

3. Process according to either of claims 1-2, characterised in that a Li-alkyl compound is used as base.

4. Process according to any one of claims 1-3, characterised in that butyllithium is used as base.

5. Process according to any one of claims 1-4, characterised in that use is made of a tri-ring- substituted β-haloethylcyclopentadiene.

6. Process according to any one of claims 1-4, characterised in that use is made of a tetra-ring- substituted β-haloethylcyclopentadiene.

7. Process according to any one of claims 1-6, characterised in that the ring substituent is chosen from the group formed by methyl, ethyl, propyl, isopropyl or phenyl.

8. Process according to any one of claims 1-7, characterised in that use is made of an at least mono-ring-substituted β-haloethylcyclopentadiene obtained by alkylation of the corresponding, at least mono-substituted cyclopentadiene.

9. Process according to any one of claims 1-8, characterised in that use is made of an at least mono-ring-substituted β-Cl-ethylcyclopentadiene.

10, Spiro[2.4]hepta-4,6-diene of the formula:

characterised in that the cyclopentadienyl ring contains two substituents.

11. Spiro[2.4]hepta-4,6-diene of the formula:

characterised in that the cyclopentadienyl ring contains three substituents.

12. Spiro[2.4]hepta-4,6-diene of the formula:

characterised in that the cyclopentadienyl ring contains four substituents. 13 SHD according to any one of claims 10-12, characterised in that the cyclopentadienyl ring contains methyl substituents.