DD271700A1 - PROCESS FOR PREPARING 1,1-DICHLOR-4-METHYL-PENTA-1,3-DIENE - Google Patents

Abstract

The invention relates to a process for the preparation of 1,1-dichloro-4-methylpenta-1,3-diene, which is an important intermediate for the synthesis of pyrethroids. The invention relates to the synthesis of 1,1,3,4-tetrachloro-4-methylpent-1-ene from 1,1,1-trichloro-4-methylpent-3-en-2-ol, 1,1,1 Trichloro-4-methylpent-4-en-2-ol or 1,1,1,4-tetrachloro-4-methylpentan-2-ol by reaction with thionyl chloride in the presence of a Lewis acid and reduction of the tetrachloro-pentane to 1, 1-dichloro-4-methyl penta-1,3-diene.

Description

Field of application of the invention

The invention relates to a process for the preparation of 1,1-dichloro-4-methylpenta-1,3-diene, which is an important intermediate for the preparation of pyrethroids.

Characteristic of the known technical solutions The 1,1-dichloro-4-methylpenta-1,3-diene is an important intermediate for the synthesis of insecticidally active Pyrethroids (D. ArIt, M. Jautelat, R. Lantzsch, Angewandte Chemie 93 1981 719). One way of representing this compound is by sequential dehydrohalogenation and Dehydration of the 1, 1-trichloro-4-hydroxy-4-methylpentane formed from 2-methylbut-3-en-2-ol and chloroform

(DE-OS 2536503, DE-OS 2536504). Here, however, the occurrence of by-products adversely affects the

Economics of this synthesis variant. Another method is the reaction of isobutylene with trichlorethylene at high temperatures (DE-OS 2639868). The Reaction rate of the reaction is very low. In the art, 1,1-dichloro-4-methylpenta-1,3-diene is passed through several stages

from chloral and isobutylene (J.Farkas, P. Kourim, F.Sorm, Coll. Czech Chem. Commun. 1959, 229, 2230). In the

Reaction of both starting materials in the presence of a Lewis acid is a mixture consisting of 1,1, i-TrichloM-methylpenM-

obtained by acid isomerization in pure "1,1,1-trichloro-4-methylpent-3-ene 2-ol can be transferred. Subsequent acylation and reduction with zinc allows access to the α, i-dicnloM-methylpenti-I.S-diene. The two steps were varied several times (DE-OS 3414371; DE-OS 3224162).

A major disadvantage is the number of synthetic steps and the forced attack of polluting Metallchloridschlämmen. It has therefore been proposed that 1,1,1-trichloromethylpent-S-ene -ol with thionyl chloride is converted to 1,1,1,4-tetrachloro-4-

Implement methylpent-2-en (DE-OS 3208385) and then to dehalogenate. But this also requires expensive

Reducing agent. The alternative proposed catalytic hydrogenation, however, sets a high purity of Feedstock ahead.

Object of the invention

The object of the invention is the production of 1,1-dichloro-4-methylpenta-1,3-diene in a simple and cheap manner in which the production of by-products is low.

Explanation of the essence of the invention

The object of the invention is to provide a process for the preparation of 1,1-dichloro-4-methylpenta-1,3-diene, which does not require expensive reducing agents and high purity of the starting materials.

According to the invention, reaction of iii-trichloro-methylpent-S-ene -ol, 1,1,1-trichloro-4-methylpent-4-en-2-ol or 1,1,1-tetrachloromethylpentane. ol with 1,1,3,4-tetrachloro-4-methylpent-1-ene with thionyl chloride at temperatures of 40-12O ⁰ C in the presence of a Lewis acid in a one-pot reaction cathodically or chemically to 1,1-dichloro-4 reduced methylpenta-1,3-diene.

In contrast to the known reaction of 1,1,1-trichloro-4-methylpent-3-en-2-ol (I) with thionyl chloride, which gives a mixture of polychloro compounds with 1,1,1,4-tetrachloro-4- methylpent-2-en ALTT main product leads unii the subsequent allyl rearrangement at 160 ⁰ CWhen 1,1,3,4-tetrachloro-4-methyl-pent-1-ene (||) (! .Bitter, LTöke, Z.Bande, e Karpati-Adam, R. Soos; Tetrahedron 40 1984 4501), it has been found that the rearrangement proceeds in the presence of Lewis acids at temperatures of 4CMOO ⁰ C and both synthetic steps can be combined.

In the reaction of I with thionyl chloride in the presence of Lewis acids, such as. As zinc, aluminum, tin IV, iron, VIII or titanium IV halides, we. achieved yields of up to 60%. Apart from a polymeric residue, 1,1,5-trichloro-4-metylpenta-1,3-diene is also a by-product in a proportion of up to 20%, which is easily separated by vacuum distillation.

OH _{ru Qnpl} Cl Cl CCl, -CH-CH = C ° = CCIp = CH-CH-C-CH,

^{Λ N}CH₃ Lewis acid* £_H

I II

The reaction to II is carried out in the presence of an inert solvent such. As chloroform, carbon tetrachloride, 1,2-dichloroethane, benzene, toluene or Ν, Ν-dimethylformamide, or without solvent in a temperature range of 40-12O ⁰ C (but preferably at 75-85 ⁰ C) performed. The thionyl chloride is used in a molar excess of 10-50% and the Lewis acid in a molar amount of 1-10% based on I-.

For the synthesis of compound II also other starting materials can be used. For this are both 1,1,1-trichloro-4-methylpent-4-en-2-ol, the product of the Prins reaction of the chloral with isobutylene, as well as its quantitatively accessible HCI adduct, the 1,1,1, 4-Tetrachloro-4-methylpentan-2-oi, usable. Reaction of both compounds with thionyl chloride in the presence of a Lewis acid under the above conditions allows for material yields of up to about 50%. Also in these reactions, the already mentioned, easily separable 1,1,5-trichloro-4-methylpenta-1,3-diene is formed as a by-product.

In addition, it was found that the LI ^ / l-TetrachloM-methylpent-i-en can be smoothly reduced to i.i-DichloHl-methylpenta-I.S-diene. The reduction to diene is possible both electrochemically and with chemical reducing agents. By a suitable choice of conditions, it is possible to proceed the reaction with a high selectivity and a very good yield.

The electrochemical reduction takes place in a divided cell, wherein the anode and the cathode space are separated by a diaphragm. For the cathode, materials with a high hydrogen overvoltage such as lead, cadmium, zinc, their amalgams or mercury are used. The anode material used is graphite, platinum or noble metal-coated titanium electrodes. The catholyte is preferably a water-miscible solvent such as alcohol (C ₁ -Cs), acetonitrile, NN-dimethylformamide, tetrahydrofuran, N-methylpyrrolidone or 1,4-dioxane and an alkali, alkaline earth metal ammonium halide. Suitable conducting salts are also the corresponding perchlorates, sulfates or nitrates. The composition of the anolyte is chosen analogously. However, it is also possible to use aqueous alkali salt solutions. The electrolysis can be carried out under galvanostatic as well as under potentiostatic conditions. Taking advantage of the potentiostatic mode of operation is carried out at a potential of E = -1.7 V against a saturated Kalomelektrode. In the case of galvanostatic conditions, it is expedient to stop the electrolysis after 110-120% of the theoretically required charge amount.

After completion of the electrolysis, the catholyte is concentrated. The addition of an excess of water leads to phase separation. Thereafter, the organics are extracted with a nonpolar solvent such as perrian or methylene chloride. After drying and concentration of the organic Exirakte carried out a purification by distillation. The diene came to be obtained in this way in a yield of about 80% with a high purity. Similar results are also achieved by the use of amalgamated zinc, iron or aluminum shavings as reducing agents. The solvents used are preferably alcohols (C ₁ -C ₆ ). However, ar.ch uses other water-miscible liquids. The reaction with the reducing agents mentioned are ir 'a temperature range of 60-100 ⁰ C. The work-up is analogous to that of the catholyte in the electrochemical reduction, whereby likewise a product of high purity can be isolated.

Finally, the catalytic hydrogenation with hydrogen leads you to the desired diene. Under atmospheric pressure and in the presence of a base such. As triethylamine or potash, hydrogenation in an alkanol-type solvent or in acetone on a Raney nickel framework catalyst is possible.

-3- 271700 embodiments:

example 1

The mixture of 50 g of i.i.i-TrichloM-methylpent-a-en ^ -ol, 1.65 g of zinc chloride, 1 ml of Ν, Ν-dimethylformamide and 200 ml of 1,2-dichloroethane is added dropwise at room temperature with 20.15 ml of thionyl chloride. The mixture is then heated under reflux for two hours. The cooled reaction product is poured into ice-water and the organic phase separated. After extracting the aqueous solution with 1,2-dichloroethane, the combined extracts are washed with a saturated sodium hydrogen carbonate solution and then again with water. This is followed by drying over sodium sulfate and distilling off the 1,2-dichloroethane. By a fractional distillation, the 1,1,3,4-tetrachloro-4-methylpent-1-ene can be isolated.

Bp 86-88 ⁰ C 1600PA Yield: 32.5 g (60%)

¹ H-NMR (CDCl ₃ ), δ in ppm

6,11 -CH = CCI ₂ , 4,69-CHCK 1,66 Ck ₃ -

MS (m / e ⁺ ): 220 (14th M ⁺ ), 185 (28), 149 (35), 77 (100)

The use of the same molar amount of aluminum chloride as the catalyst instead of zinc chloride allows a yield of 66% of 1,1,3,4-tetrachloro-4-methylpent-1-ene, whereas the use of stannic chloride reduces the isolation of 57% product possible.

Reactions with the 1,1,1-trichloro-4-methylpont-4-en-2-ol or 1,1,1,4-tetrachloro-4-methylpentan-2-ol according to the procedure described above lead to yields of 46 and 51% of product respectively.

Example 2 mercury 0.1 M LiCl / methanol 180 mL 12 g I.I.S.sup.-1-tetrachloromethylpenyl Potent! Dstatic electrolysis Platinum Network • cathode: 4,5MLiCI / Wasser25ml catholyte: G5 frit Anode: 15-2O ⁰ C anolyte: -1.7V vs. SCE diaphragm: Temperature: Potential:

After the current has dropped to the value of the background current, the electrolysis can be stopped. The catholyte is separated from mercury, concentrated to about 40 ml and extracted several times with pentane after the addition of 250 ml of water. The combined extracts are washed with water, then dried over sodium sulfate and concentrated. The crude product is finally distilled in vacuo.

Kp 50-52 ⁰ C 1300Pa Yield: 6.3 g of diene (77T.

Example 3 lead 0.2M NaCl / methanol 180ml 12g i.i ^ tetrachloromethylpent-i-ene Galvanostatic electrolysis graphite Cathode: 2MNaCl / water 120 ml catholyte: Nafion membrane 427 Anode: 25 ⁰ C anolyte: 6mA / cm ² diaphragm: Temperature: Current density:

The electrolysis is stopped after the passage of 110% of the theoretically required amount of charge. The catholyte is concentrated to about 40 ml and extracted several times with methylene chloride after the addition of 250 ml of water. After washing the immortalized extracts with water, they are dried over sodium sulfate and then concentrated. The crude product is distilled in vacuo.

Yield: 6.4g diene (78%) Example 4

To 22.2 g of 1,1,3,4-tetrachloro-4-methylpan-M-en are added 8.6 g of zinc powder, 0.27 g of mercuric chloride and 150 ml of ethanol. The mixture is then heated under reflux for four hours. After dom filtering off the solids, the alcoholic solution is concentrated and treated with an excess of water. The organic components are extracted by repeated treatment with pentane. Dia combined extracts are washed with a little water, dried over sodium sulfate and concentrated. Finally, the diene is purified by vacuum distillation.

Yield: 10.3 g of diene (68%) Example 5

The mixture of 22.2 g of 1,1,3,4-tetrachloro-4-methylpent-1-ene, 200 ml of ethanol, 20.2 g of triethylamine and 4 g of Raney nickel is added under atmospheric pressure and at room temperature with hydrogen. After receiving an equimolar amount of hydrogen, the catalyst is filtered off, the solvent is distilled off and the concentrated Fiitrat mixed with 250 ml of water. The solution is extracted several times with pentane. The combined extracts are washed with water and then dried over sodium sulfate. After distilling off the pentenes at atmospheric pressure is distilled in vacuo.

Yield: 10.6 g of diene (70%)

Claims (7)

1. A process for the preparation of!, I-dichloro-methylpenta-i, 3-diene, characterized in that by reaction of!, Ii-trichloro-methylpent-S-en ^ -ol, 1,1,1- trichloro-4-methylpent-4-en-2-ol or 1,1 _f 1 _f 4-tetrachloro-4-methyl pentan-2-ol with thionyl chloride in the presence of a Lewis acid in a one-pot reaction arising 1,1,3,4 Tetrachloro-4-methylpent-1-ene is cathodically or chemically reduced to 1,1-dichloro-4-methylpenta-1,3-diene. 2. The method according to claim 1, characterized in that the thionyl chloride in a molar excess of 10-50% and the Lewis acid such. As aluminum, zinc, tin IV, titanium IV or ferric halide in a molar amount of 1-10% based on the polychloroalcohols - can be used. 3. The method according to claim 1 and 2, characterized in that the reactions are carried out with thionyl chloride without solvent or in the presence of an inert solvent such as chlorinated hydrocarbons, benzene, toluene or xylene at a temperature of 40-120 ⁰ C. 4. The method according to Ansprucn 1, characterized in that the electrochemical reduction takes place in a divided cell of cathode materials with a high hydrogen overvoltage such as lead, zinc, cadmium, their amalgam or mercury both under galvanostatic and potentiostatic operation at room temperature. 5. The method according to claim 1 and 4, characterized in that the catholyte is a water-miscible solvent, such as Ci-C ₆ -alcohols, Ν, Ν-dimethylfoimamide, acetonitrile, tetrahydrofuran or 1,4-dioxane, in conjunction with alkali -, alkaline earth or Ammoi liumhalogeniden, sulfates, perchlorates or nitrates find application, while for the Ar.olyten in addition to the compositions mentioned for the catholyte and the use of aqueous alkali salt solutions is possible. 6. The method according to claim 1, characterized in that the reduction with amalgamated metal powder (zinc, aluminum, iron) in alkanol-type solvents in the temperature range of 60-100 ⁰ C is performed. 7. The method according to claim 1, characterized in that the reduction is carried out as a catalytic hydrogenation on a Raney nickel framework catalyst in the presence of a base and a water-miscible solvent such as alcohols or acetone at a temperature in the range of 10-60 ⁰ C. ,