CS215474B1 - Process for preparing conjugated dienes - Google Patents

Abstract

The invention relates to a catalytic process for the preparation of conjugated dienes from isomeric unconjugated dienes by the action of titanocene derivatives. The process for the preparation of conjugated dienes consists in treating isomeric unconjugated dienes with a catalyst consisting of bis (η5-cyclopentadienyl)titanium dichloride (C5H5)2TiCl2 and lithium aluminum hydride LiAlH4 in a molar ratio of Ti : AI = 1:1 — 1:6 at a temperature of 60—200 °C or (η5 : T)5-fulvalene)di-g-hydrido-bis(Ti5-cyclopentadienyltitanium) at a temperature of 140-200 °C, after which the conjugated diene is isolated from the reaction mixture, preferably by distillation.

Description

The present invention relates to a catalytic process for the preparation of conjugated dienes from isomeric unconjugated dienes by titanocene derivatives.

Syntheses of conjugated dienes are based on the Wittig reaction (A. Maercker: Org. Reactions 14, 270 (1965)), the bonding of alkenyls with all snyl groups (Posner GH: Org. Reactions Γ253 (1975)), and various elimination reactions (Von Brachel H., Bahr U .: Houben-Weyl, Methoden der Organisehen Chemie Band 5 (lc), Teil 3, Georg Thieme Verlag, Stuttgart, (1970). The first method, although used in the pharmaceutical industry (H. Pommer, Nurrenbach A .: Pure Appl. Chem. 43, 527 (1975)), is not suitable for mass production due to relatively high labor and cost. The second method, although general, is limited to laboratory use, and the third method is not generally applicable and generally provides high yields.

Co-conjugated dienes are the starting material of numerous syntheses, particularly Diels-Alder additions, eat monomeric raw materials for the preparation of polybutadiene rubber-type polyolefins and are oligomerizable to linear and cyclic dimers and trimers.

The present invention is a process for the preparation of conjugated dienes consisting of the action of a catalyst composed of bis (cyclopentadienyl q ⁵⁾ titanium dichloride (C ₅ H _{5) 2} TiCl ₂ and lithium aluminum hydride LíA1H ₄ mol. Ti: Al ratio = 1: 1 - 1: 6, to isomeric unconjugated dienes at 60-200 ° C or in the action of (η ⁵ : q ⁵ -fulal) di-q-hydrido-bis (q ⁵ -cyclopentadienyl titanate) on the same substrates at 140-200 ° C and visolalation of the conjugated diene by distillation from the reaction mixture at normal or reduced pressure.

The isomerization reaction of the dienes with the (C ₅ H ₅ ) ₂ TiCl ₂ catalyst is carried out under an argon or nitrogen atmosphere, generally with the boiling of the unconjugated diene. (C ₅ H ₅ ) ₂ TiCl ₂ is bound and dosed without any limitation, the same operations with LiAlH ₄ must be carried out in a dry atmosphere or in air, but for less than one minute.

(η ⁵ : r) ⁵ -fulvalene) di (4-hydrido-bis (r) ^5- cyclopentadienyl titanate) is best prepared by reduction of (C ₅ H ₅ ) ₂ -TiCl _{2 with} lithium aluminum hydride in xylenes or mesitylene (Antropiusóvá H., Dosedlová A , Hanus V., Mach K .: Transition Met, Chem. In press), and thus the obtained solution of this catalyst compound in an aromatic solvent can be used to isomerize unconjugated diene in a sealed vial or pressure vessel. The condition for the efficiency of the catalysts is the high purity of the unconjugated dienes and, in particular, the absence of oxygen containing active hydrogen, such as acids, alcohols, aldehydes, ketones, epoxides, unsaturated ethers and the like. The selectivity of the two catalysts is virtually identical, and the choice of catalysts depends, among other things, on the amount of substrate. Catalyst (C ₅ H ₅ ) ₂ TiCl ₂ - LiAlH ₄ is suitable for the preparation of at least 20 cm ^{3 of} diene, in large amounts it is necessary to ensure efficient heat dissipation during isomerization, because the reaction is exothermic. Any small amount of dienes can be isomerized with the fulvalene titanium catalyst, and the maximum amount is not limited. The above-mentioned impurities mainly deactivate the catalyst; for a diene purified by contact with a fulvalen titanium complex at a temperature of up to 120 ° C, it can be completely converted at a molar ratio catalyst: diene = 1: 10 ⁴ .

Said catalysts isomerize, for example, 1,5-hexadiene to 1,4-hexadiene to 2,4-hexadiene, 2,5-dimethyl-1,5-hexadiene to 2,5-dimethyl-2,4-hexadiene, 3-methyl-1,3-hexadiene; 5-heptadiene to 3-methyl-2,4-heptadiene, 2-methyl-1,5-hexadiene to 2-methyl-2,4-hexadiene, 4-vinylcyclohexene to 3-ethylidenecyclohexene and 1,7-octadiene to 1: 2 mixture 2,4-octadiene and 3,5-octadiene. The conversion of the original hydrocarbon is always 100% and the products are obtained in a purity of at least 98%. $

All conjugated dienes will become affordable by this process since the starting materials are commercially prepared by both the cumulation of allhalhalides and the corresponding halides. methallyl halides by magnesium, diol dehydration or catalytically dimerizing butadiene (U.S. Patent 3,444,253 (1969) and U.S. Patent 3,497,462 (1970)), respectively. coupling of butadiene with ethylene (Alderson T .: U.S. Pat. 3,013,066 (1961)).

All products can be used as monomers for the preparation of polybutadiene methyl derivative, as diene component in Diels-Alder syntheses and as monomers for catalytic preparation of linear and cyclic dimers and trimers.

The invention is further illustrated by the following examples without being limited thereto.

Hydrocarbon analysis was performed by gas chromatography coupled to mass spectrometric detection (GCMS). Identification of hydrocarbons is performed by measuring ³ H and ¹³ H ¹ NřjlR spectra, i. No. Of spectra and comparison of physical constants with literature data.

Example 1

Weigh ± 0.25 g (C ₅ H ₅ ) ₂ TiCl ₂ (1 mmol) and 0.15 g LiAlH ₄ (4 mmol) into a two-necked flask equipped with a magnetic stirrer and thermometer. Then 78 g of 1,5-hexadiene (1 mol) were added under argon and the mixture was boiled under stirring (60-64 ° C) for 10 hours. Then, the product is distilled off at normal pressure (64 ° C) to give 76 g of a mixture consisting of a gas chromatic ahalyse of 44% E, E-2,4-hexadiene, 37% E, Z2,4-hexadiene, 17% Z, Z-2,4-hexadiene and 2%

1,4- hexadiene. The distillation residue is poured under argon with 20 ml of toluene-ethanol (2: 1 v / v) and is deactivated with water after the hydrogen evolution ceases.

Example 2

4-Vinylcyclohexene is isomerized in the same manner as hexadiene in Example 1, except that the reaction mixture prepared from 0.25 g (C ₃ H ₅ ) ₂ TiCl ₂ , 0.15 g L1AlH 4 and 108 g 4-vinylcyclohexene is boiled at 130 ° C for 2 hours. Distillation under reduced pressure yielded 104 g of a product consisting of 99.5% 3-ethylidenecyclohexene and 0.5% 4-ethylidenecyclohexene. The catalyst is deactivated as in Example 1.

Example 3

Preparation of 0,033 M solution (η ⁵ : rp ⁵ -fulvalene) of di-p-hydrido-bis (cyclopentadienyl titanate) in benzene:

0.25 g (C ₅ H ₅ ) ₂ TiCl ₂ (1 mmol) and 0.15 g LiAlH ₄ (4 mmol) in a mixture with 40 cm ^{3 of} mesitylene are heated at 140 ° C for 1 hour under argon atmosphere. After cooling, the green solution of the desired product is cast from the black undissolved reaction residue. The mosque flax is distilled off in vacuo and 33 cm ^{3 of} benzene is distilled off in the gray-green residue. The light green solution was poured from the remains of a black precipitate and dispensed into ampoules of 3 cm ³ . The black precipitate is self-igniting in air and in contact with water and is therefore deactivated with toluene-ethanol (2: 1 v / v) with limited air access.

Claims (2)

SUBJECT i Process for preparing conjugated dienes, characterized in that isomerically unconjugated dienes are treated with a catalyst consisting of bis (β ⁵ -cyclopentadienyl) titanium dichloride (C ₅ H ₅ ) ₂ -TiCl ₂ and lithium aluminum hydride LiAlH ₄ in mol. ratio Ti: Al To an evacuated ampoule containing (η ⁵ ? Η ⁵ -fulvalene) di-g-hydrido-bis (cyclopentadienyl titanate) (0.1 mmol), obtained by evaporation of 3 cm ^{3 of the} above prepared benzene solution, is distilled 2,5-dimethyl-1,5-hexadiene (110 g) (1 mol) and the vial is melted. After heating at 180 ° C for 5 hours and cooling to room temperature, the contents of the vial are distilled off under a vacuum of 10 ^-2 Torr into a dry ice-cooled sample. 106 g of a product consisting of 99.5% 2,5-dimethyl-2,4-hexadiene and 0.5% 2,5-dimethyl-1,4-hexadiene were obtained. Example 4 The isomerization of 4-vinylcyclohexene is carried out as in Example 3, except that 108 g of diene is heated with 0.1 mmol of catalyst at 170 ° C for 4 hours. The distilled product (104 g) contains 99.5% of 3-ethylidencyclohexene and 0.5% of 4-ethylidencyclohexene. INVENTION 1: 1 to 1: 6 at a temperature of 60-200 ° C or (η ^5: T) ^{of 5} -fulvalen) di-p-hydrido-bis (eta] ⁵ -cyklopentadienyltitan) cm at a temperature of 140-200 ° C, wherein the conjugated diene is isolated from the reaction mixture, preferably by distillation.