WO2005044764A2

WO2005044764A2 - Method for the production of cyclooctatetraene

Info

Publication number: WO2005044764A2
Application number: PCT/DE2004/002337
Authority: WO
Inventors: Frank Thomas Edelmann; Jochen Gottfriedsen
Original assignee: Otto-Von-Guericke- Universität Magdeburg
Priority date: 2003-10-24
Filing date: 2004-10-20
Publication date: 2005-05-19
Also published as: WO2005044764A3; DE10349993A1

Abstract

The invention relates to a method for the simple, safe, economic and environmentally friendly production of cyclooctatetraene C8H8 (1). In a particularly preferred embodiment, the inventive method consists in converting 1,5-cyclooctadiene into lithium salt of the cyclooctatetraene dianion, Li2C8H8, and subsequent oxidation of said intermediate product by means of di-tert-butylperoxide in order to form cyclooctatetraene. The inventive method is simple, can be carried out in a safe manner and enables pure cyclooctatetraene to be produced with yields amounting up to 60-70 %. The production of cyclooctatetraene according to the inventive method is, above all, economical and environmentally friendly due to the security requirements being low, the starting materials being commercially accessible, in-expensive and no toxic heavy metal compounds being used.

Description

description

Process for the preparation of cyclooctatetraene

The present invention relates to a process for the preparation of cyclooctatetraene by converting 1,5-cyclooctadiene into cyclooctatetraene. The process is simple, safe, inexpensive and environmentally friendly.

Cyclooctatetraen, CsHs (1), and the derived dianion CsHs ^{2 "} are important starting materials and reagents both in organic synthesis and in organometallic chemistry (see GI Fray, RG Saxton: The Chemistry of Cyclooctatetraene and Its Derivatives, Cambridge University Press, Cambridge, 1978, pp. 172-189).

However, the processes known from the prior art for producing cyclooctatetraene are generally associated with major disadvantages. Some of these procedures are difficult to perform on a laboratory scale, while others provide poor yields or require the use of toxic heavy metal reagents. The classic Reppe process involves the tetramerization of acetylene, HC≡CH, in the presence of nickel catalysts (see, for example, US Pat. Nos. 2,579,106, 2,613,231 and 2,903,491, and GB Patent No. 706 629). However, all of these processes involve the use of the highly flammable and potentially explosive acetylene under high pressure and can therefore only be carried out safely on an industrial scale. The large-scale production of cyclooctatetraene by the Reppe process from acetylene has also recently ceased, which has led to the fact that commercially available cyclooctatetraene is becoming increasingly expensive. There is therefore a great need for a simpler and safer process using inexpensive and easily accessible starting materials. Attempts have also been reported in the prior art to oxidize the cyclooctatetraene dianion, CsHa ^{2 "} , which is obtainable in various ways, to suitable cyclooctatetraene using suitable oxidizing agents. The conversion of the easily accessible and inexpensive 1, 5-cyclooctadiene into the cyclooctatetraen dianion has ended well known in the art {see W. Gausing, G. Wilke, Angew. Chem. 1978, 90, 380; Angew. Chem. Int. Ed. Engl. 1978, 17, 371; NC Burton, FGN Cloke, SCP Joseph, H. Karamallakis, AA Sameh, J. Organomet. Chem. 1993, 462, 39-43) In the process described by Gausing and Wilke, CdCI _{2 is used} as an oxidizing agent, which is highly toxic and therefore in the synthesis of The alternative oxidizing agent phenyl sodium (CβHsNa) is not commercially available and is of safety concern because the intermediate product Na ₂ COT formed during the reaction is explosive.

By Roesky et al. the conversion of the lithium salt LiaCsHs produced in the presence of N, N, N ', N'-tetramethylethylenediamine (= TMEDA) with mercury (II) chloride, HgCI ₂ , has been described (TG Wetzel, S. Dehn, PW Roesky, Organometallics 1999, 18, 3835-3842). Although this process provides cyclooctatetraene in a yield of 45%, it also has the major disadvantage of using highly toxic mercury (II) chloride. For environmental reasons, the process is therefore not very suitable for producing larger amounts of cyclooctatetraene. Simons and Lagowski have recently reported that the oxidation of the dipotassium salt feCsHs with atmospheric oxygen or elemental iodine leads to the formation of cyclooctatetraene (Tetrahedron Letters 2002, 43, 1771-1773). This process also has serious disadvantages: the dipotassium salt used as the starting material

is highly explosive even with the slightest contact with oxygen and is therefore very difficult to handle. The controlled oxidation of I ^ CsHs also provides explosive residues that are sensitive to pressure and heat. In contrast, oxidation with elemental iodine only gives a cyclooctatetraene yield of 22%. For these reasons, the methods published by Simons and Lagowski are not very suitable for a safe and practical synthesis.

Based on these disadvantages of the methods from the prior art, the object of the invention is to provide a simple, safe and inexpensive method for producing cyclooctatetraene by converting To create 1, 5-cyclooctadiene in cyclooctatetraene, which is also as environmentally friendly as possible and does not use toxic heavy metals. To solve this problem, the inventors have carried out extensive studies on the conversion of the cyclooctatetraene dianion, CsHs ^{2 "} , which is readily accessible from 1,5-cyclooctadiene, into cyclooctatetraene and surprisingly found that this object is achieved by a method having the features of claim 1 ,

According to one aspect of the present invention, the inexpensive and large amounts of 1,5-cyclooctadiene which is available are used as the starting material. This is first converted into the cyclooctatetraene dianion, CsHa ^{2 "} , by methods which are well known in the art. It can be in the form of its salts with alkali or alkaline earth metals. Preferred metal cations are lithium, sodium, potassium, Rubidium, cesium and magnesium, with lithium being the most preferred. A particularly suitable metalation reagent is π-butyllithium in the presence of N, N, N ', N'-tetramethylethylene diamine (TMEDA). A preferred embodiment of the present invention involves the use of the latter In the process according to the invention, the salt of the cyclooctatetraen dianion thus prepared is oxidized to the cyclooctatetraen in a smooth reaction by adding a suitable diorganoperoxide.

The diorganoperoxides of the general formula ROOR 'used as oxidizing agents according to the invention are outstandingly suitable for the smooth oxidation of the cyclooctatetraene dianion with the formation of cyclooctatetraene. In the general formula ROOR ', R and R' can be the same or different and are selected from the group consisting of alkyl groups with 1-20 carbon atoms, cycloalkyl groups with 3-20 carbon atoms, aryl groups with 6-26 carbon atoms, aliphatic or aromatic acyl groups ( RC (O)) with 2-26 carbon atoms and triorganosilyl groups with 3-60 carbon atoms.

Exemplary alkyl groups include methyl, ethyl, propyl, / ^' so-propyl, butyl, sec-butyl, fe / ϊ-butyl, pentyl, e / t-pentyl, hexyl, heptyl, octyl, fe / f-octyl, nonyl, decyl and hexadecyl; exemplary cycloalkyl groups include cyclopentyl, cyclohexyl, cycloheptyl and menthyl; exemplary aryl groups include phenyl, tolyl, xylyl, mesityl, naphthyl and anthryl; exemplary acyl groups include acetyl, Propionyl, n-butyroyl, sec-butyroyl, pivaloyl, benzoyl, substituted benzoyl, mesitoyl and naphthoyl.

Among these, the dialkyl peroxides are particularly preferred. Particularly preferred examples include, for example, di-fe / f-butyl peroxide and di-fe / f-octyl peroxide, with the use of di-fe / f-butyl peroxide being the most preferred embodiment. The di-fe / f-butyl peroxide offers a number of advantages which make it an excellent reagent for carrying out the process according to the invention. Di-fe / f-butyl peroxide is a diorganoperoxide that is stable and easy to handle under normal conditions. It is commercially available and inexpensive. In the production of cyclooctatetraene by the process according to the invention using di-fe / f-butyl peroxide, a by-product is fe / f-butanol, which is easy to remove and does not pose any environmental pollution. The method according to the invention using di-fe / f-butyl peroxide can therefore be carried out simply and safely and is also inexpensive and environmentally friendly.

When selecting the reaction temperature, only the requirement familiar to the person skilled in the art should be observed that the reaction solvents and the diorganoperoxides are present in the liquid phase. The reaction temperature is therefore generally in a range between approximately 0 ° C. and 120 ° C., a range between approximately 20 ° C. and 80 ° C. being preferred. The reaction pressure is not particularly limited. The method according to the invention is usually carried out at normal pressure.

All organic solvents which do not react with the reagents and intermediates used are suitable as reaction solvents. Inert organic solvents, such as, for example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and ethers, are therefore particularly suitable. The preferred organic solvents which are suitable for the process according to the invention include, in particular, aliphatic hydrocarbons and ethers. Suitable solvents include, but are not limited to, n-pentane,? -Hexane, π-heptane, π-octane, isooctane, diethyl ether, methyl-fe / f-butyl ether, di - /? - butyl ether and tetrahydrofuran, with pentane, hexane and diethyl ether are preferred. Most preferred are π-pentane and π-hexane. The method according to the invention can be carried out in normal laboratory equipment made of glass or metal, although these are not particularly restricted. The cyclooctatetraene formed is isolated by simple processes, such as extraction and distillation, which are well known from the prior art (see, for example, Houben-Weyl, Methods of Organic Chemistry, Volume 3, 4th Edition, Georg Thieme Verlag, Stuttgart). By simple fractional distillation, pure cyclooctatetraene can be isolated in good yields of approx. 60-70% as a yellow liquid. It was clearly characterized by its physical data, especially its boiling point and ¹ H-NMR spectrum.

In its preferred embodiment, the process according to the invention for the preparation of cyclooctatetraene provides a cyclooctatetraene synthesis which is simple to carry out on a laboratory scale and also at least on a small industrial scale because the safety requirements are low and the starting materials are commercially available and inexpensive. To the knowledge of the inventors, the process according to the invention is the first process for the preparation of cyclooctatetraene, which does not require explosive or toxic starting materials or by-products. The method according to the invention thus offers significant advantages over the methods from the prior art.

The invention will now be described in more detail with reference to exemplary embodiments. It is to be assumed that these exemplary embodiments are only illustrative in nature and are in no way intended to limit the invention. It will be apparent to those skilled in the art of synthetic organic chemistry that various modifications and additions can be made without departing from the spirit of the invention.

Embodiment 1

(10 g scale reaction)

In a 500 ml three-necked flask with a reflux condenser, dropping funnel and argon inlet, π-butyllithium (153 ml of a 1.6 M solution in n-hexane, 0.245 mol) was added dropwise to a stirred solution of 1,5-cyclooctadiene (10 ml, 0.082 mol) in Pentane (80 ml) added. Then 37 ml of TMEDA (N, N, N ', N'-tetramethylethylenediamine) was added dropwise, and the orange-yellow Reaction mixture stirred for 24 h to complete the formation of Li ₂ C8H ₈ . Di-fe / f-butyl peroxide (32.4 ml, 0.177 mol) was added dropwise with thorough stirring, during which the reaction mixture warmed to boiling. The mixture was then heated under reflux with stirring for 4 h in order to complete the reaction. After cooling to room temperature, the organic phase was separated, washed with water (3 × 250 ml) and ammonium chloride solution (3 × 250 ml) and dried over anhydrous MgSO ₄ . The solvent was removed on a rotary evaporator at 40 ° C. and the residue was fractionally distilled at normal pressure. The fraction boiling at 142-143 ° C consisted of pure cyclooctatetraene. Yield: 5.3 g (62%). ¹ H-NMR (CDCI ₃ , 400 MHz): δ = 5.77 (s, 8H) ppm

Embodiment 2

(Reaction on a larger scale)

The procedure according to the exemplary embodiment was essentially repeated, except that 45 ml (0.367 mol) of 1,5-cyclooctadiene in 370 ml of pentane, 690 ml of n-butyllithium solution (1.6 M in n-hexane), 166 ml (1, 10 mol) TMEDA and 67.4 ml (0.796 mol) di-fe / f-butyl peroxide were used. The organic phase was diluted with 200π pentane, washed with 1% acetic acid (6 x 150 ml) and then with saturated NaHCO ₃ solution (3 x 150 ml) and dried over MgSO ₄ . Distillation as in Example 1 gave 24.85 g (65%) of cyclooctatetraene as a yellow liquid with a boiling point of 142-143 ° C. ¹ H-NMR (CDC, 400 MHz): δ = 5.77 (s, 8H) ppm

Claims

claims

1. Process for the preparation of cyclooctatetraene, C ₈ H ₈ , by oxidation of the cyclooctatetraene dianion, CsHs ^{2 "} , using diorganoperoxides of the general formula ROOR ', in which R and R' may be the same or different and are selected from the group consisting of consists of alkyl groups with 1-20 carbon atoms, cycloalkyl groups with 3-20 carbon atoms, aryl groups with 6-26 carbon atoms, aliphatic or aromatic acyl groups (RC (O)) with 2-26 carbon atoms and triorganosilyl groups with 3-60 carbon atoms.

The method of claim 1, wherein ^■ exemplary alkyl groups include methyl, ethyl, propyl, / so-propyl, butyl, sec-butyl, fe / f-butyl, pentyl, fe / f-pentyl, hexyl, heptyl, octyl, fe / f - octyl, nonyl, decyl and hexadecyl; ^Exemplary cycloalkyl groups include cyclopentyl, cyclohexyl, cycloheptyl and menthyl; ^■ exemplary aryl groups include phenyl, tolyl, xylyl, mesityl, naphthyl and anthryl; exemplary acyl groups include acetyl, propionyl, π-butyroyl, sec-butyroyl, pivaloyl, benzoyl, substituted benzoyl, mesitoyl and naphthoyl.

3. The method according to claim 1 or 2, wherein dialkyl peroxides are used as the oxidizing agent.

4. The method according to any one of claims 1 to 3, wherein di-fe / f-butyl peroxide is used as the oxidizing agent.