CH648541A5 - PREPARATION OF 1,1-DICHLOR-4-METHYL-1,3-PENTADIEN. - Google Patents

Description

The invention relates to a process for the preparation of l, l-dichloro-4-methyl-l, 3-pentadiene, in which chloral and isobutylene are reacted, then the 1,1,1-trichloro-2-hydroxy-4-methyl obtained -3-pentene of the formula I.

° \

C1 ~ C

OH

-L-

he

CH S C - CH,

CH,

reacted with thionyl chloride, advantageously in the presence of a catalyst, without solvent or in an inert solvent and finally the l, l, l, 4-tetrachloro-4-methyl-2-pentene thus obtained to 1,1-dichloro -4-methyl-1,3-pentadiene is reduced.

The l, l-dichloro-4-methyl-l, 3-pentadiene is the key intermediate in the synthesis of cyclopropane-carboxylic acid esters. According to a variant of the processes known for its production, it becomes from the 1,1,1-trichloro-4-methyl-4-hydroxy-pentane formed by the addition of 2-methyl-3-buten-2-ol and chloroform by water -, later hydrochloric acid elimination or in reverse order by dehydrohalogenation and dehydration (German publication no. 2 536 503, 2 536 504 and 2 616 528). The disadvantage of the processes is that the compound formed in the chloroform telomerization is contaminated in an amount of about 15-20% by the isomer which does not contain the trichloromethyl group at the chain end. This substance cannot be separated using physical methods, and the resulting products result in the cleaning of the

35 valuable cyclopropane-carboxylic acid esters to considerable losses.

In recent years, a number of processes have been developed with which 1,1-dichloro-40 4-methyl-1,3-pentadiene can be produced at a temperature of 400-500 ° C. in a tube reactor with continuous operation. In these processes, isobutylene is used as the starting material, which is reacted with either trichlorethylene or with 1,1-dichloroethylene in the presence of peroxide catalysts (British Patent No. 1,532,676; German Offenlegungsschrift No. 2,629,868). The main disadvantage of the method is that the product mixtures produced in this way only contain the target product in an amount of about 5-10%.

A technically simple and, in terms of the base 50 materials, the cheapest way of producing the target product is the method according to FARKAS (J. Farkas, P. Kohrim, F. Sorm: Coll. Czech. Chem. Commun. 24 2230, 1959; German Offenlegungsschrift No. 2 616 681), the 55 l, l, l-l-trichloro-2-hydroxy-4-methylpentene-3 and -4 isomer mixture which is formed in the “Prins” reaction of isobutylene and chloral being the starting material . This isomer mixture is used to produce l, l-dichloro-4-methyl-1,3-pentadiene by O-acetylation, Zn-acetic acid reduction, elimination and finally isomerization. The main disadvantage of the process is that very much - and quite expensive - zinc is required for the reductive acetoxy elimination.

The basis of the process according to the invention is the knowledge that in the “Prins” reaction in the chlorination using thionyl chloride, the l, l, l-l-trichloro-2-hydro-xy-4 that is easy to produce from simple raw materials -methyl-3-pentene the sulfur dioxide elimination of the intermediate product is accompanied by an alkyl rearrangement and in the reaction quantitative 1,1,1,4-tetrachloro-4-

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648541

methyI-2-pentene is formed, which delivers I, l-dichloro-4-methyl-l, 3-pentadiene using conventional reduction methods with almost quantitative yield.

In the process according to the invention, the procedure is advantageously such that the mixture of l, l, l-trichloro-2-hydroxy-4-methyl-3-pentene and an excess of 15-80 mol% of thionyl chloride used and advantageously 1 % By weight of dimethylformamide as a catalyst without solvent or in an inert organic solvent - advantageously in aromatic hydrocarbons or aliphatic chlorinated hydrocarbons - heated at a temperature of 40-130 C, advantageously at 60-90CC until the evolution of gas has ceased, then the excess increases Thionyl chloride or the organic solvent is removed by distillation. The crude product obtained can be used in the reduction without purification or - if necessary - (before the catalytic hydrogenation) can be purified by distillation under reduced pressure. The reduction is carried out using known methods, advantageously using amalgamated iron, aluminum or zinc powder in an alkanol (methanoI, ethanol, isopropanol) solvent at a temperature of 40-70 ° C. by catalytic hydrogenation (using a bone carbon palladium catalyst in alkanol , Acetone or acetic acid solvent at 20-60 ° C or with a Raney-Ni catalyst in alkanol solvent in the presence of a base equivalent to the resulting hydrochloric acid, advantageously triethylamine or potassium carbonate) or with sodium dithionite, in methanol, with the resulting Contains hydrochloric acid equivalent sodium hydroxide, carried out at 60 C, the product is filtered off and freed from the solvent of the reaction mixture at reduced pressure by distillation.

The following examples illustrate further details of the method according to the invention,

without restricting the present method to this.

example 1

The mixture of 90.0 g (0.44 mol) l, l, l-trichloro-2-hydroxy-4-methyl-3-pentene, 350 cm3 of solvent (aromatic hydrocarbon or aliphatic chlorinated hydrocarbon - advantageously 1,2-dichloro -ethane or benzene), further 59.5 g (0.5 mol) of thionyl chloride and 1.0 cm3 of dimethylformamide is heated to 60-80 ° C, then it is stirred at this temperature until the evolution of gas has ceased. The reaction mixture is poured into 400 cm3 of water, neutralized with NaHC03. The organic phase is isolated, dried, then the solvent is distilled off. The amount of the crude product obtained as a residue is 91.0-95.8 g (93-98%). For further cleaning, the product is fractionated at a pressure of 26 m bar.

Yield:

86.0-88.9 g l, l, l, 4-tetrachloro-4-methyl-2-pentene (88-91%), boiling point: 115-120 / 26 mbar

IR (film): 3000, 1460, 1380, 1285, 1250, 1120, 1085, 960, 840, 775, 730 cm "1

! H NMR (CDCy, 8 [ppm]: Me: 1.73 s (64); CH = CH-: 6.27d (14) 6.43d (14)

13C NMR (CDC13) ô [ppm]: Me: 32.2, Me2 CCI: 65.3, CCI: 9.40 CH = CH: 132.4.137.8

Example 2

The mixture of 90.0 g l, l, l-trichloro-2-hydroxy-4-methyl-3-pentene, 89.3 g thionyl chloride and 1.0 cm3 dimethylformamide is heated to the boil, then it becomes

The mixture is boiled until the gas evolution ceases. The excess thionyte chloride is distilled off, the residue is fractionated under reduced pressure.

Yield:

88.0 g (90%) 1,1,1,4-tetrachloro-4-methyl-2-pentene.

Example 3

The mixture of 22.2 g (0.1 mol) l, l, l, 4-tetrachloro-4-methyl-2-pentene, 150 cm3 of ethanol, 4 g (0.15 gram atom) of Al powder and 0.27 g (0.001 mol) of mercury (II) chloride is boiled for 2.5-3 hours, then the solid is filtered off, washed with ethanol. The alcohol-containing solutions are combined, the solvent is distilled off, the residue is fractionated under reduced pressure.

Yield:

13.8 g (91%) l, l-dichloro-4-methyl-l, 3-pentadiene (boiling point: 62-64 "C / 26 mbar).

In Examples 4 and 5, the procedure is as in Example 3, but iron or zinc powder is used as the reducing agent.

Example reducing agent l, l-dichloro-4-methyl-l, 3-

pentadiene g%

4 S, 2 g iron powder 13.2 87

5 8.6 g zinc powder 13.5 89

Example 6

The mixture of 22.2 g (0.1 mol) l, l, l, 4-tetrachloro-4-methyl-2-pentene, 200 cm3 of i-propanol, 1.0 g of 10% Pd / C catalyst hydrogenated at room temperature and atmospheric pressure. After an equimolar amount of hydrogen has been taken up, the catalyst is filtered out, the solvent is distilled off and the residue is fractionated under reduced pressure.

Yield:

14.0 g (92%) 1,1-dichloro-4-methyl-1,3-pentadiene.

In Examples 7 and 8, the procedure is as in Example 6, except that acetic acid or acetone is used as the solvent.

Example solvent temperature l, l-dichloro-4-methyl

1,3-pentadiene

'C g%

7 acetic acid 60 12.6 83

8 acetone 30-35 13.0 86

Example 9

The mixture of 22.2 g (0.1 mol) l, l, l, 4-tetrachloro-4-methyl-2-pentene, 200 cm3 of ethanol and 20.2 g (0.2 mol) of triethylamine and 0.4 g Raney nickel is hydrogenated with intensive shaking at room temperature and atmospheric pressure. After taking up an equimolar amount of hydrogen, the catalyst is filtered, the filtrate is sealed to 40 ml, then 200 ml of water are added. The mixture is extracted with 2 x 70 ml of dichloromethane, the dichloroethane-containing solution obtained is dried, the solvent is removed and the residue is distilled off under reduced pressure (26 mbar).

Yield:

12.6 g (83%) l, l-dichloro-4-methyl-l, 3-pentadiene.

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648 541

Example 10

Everything is carried out as in Example 9, except that 0.2 mol of potassium carbonate is used instead of triethylamine.

Yield:

12.7 g (84%) l, l-dichloro-4-methyl-l, 3-pentadiene. Example 11

In the mixture of 22.2 g (0.1 mol) of 1,1,1,4-tetrachloro-4-methyl-2-pentene, 100 cm3 of methanol and 12.0 g of sodium

The 30% aqueous solution prepared from 8 g of sodium hydroxide is instilled in dithionite, then the mixture is stirred at 60 ° C. for 3-4 hours. The mixture is evaporated to a quarter, 200 cm 3 of water are added, then extracted with 2 × 100 ml of dichloromethane. The extract is dried, the solvent is distilled off and the residue is fractionated under reduced pressure.

Yield:

12.8 g (84%) l, l-dichloro-4-methyl-l, 3-pentadiene.

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S

Claims (8)

648 541 2nd PATENT CLAIMS 1. A process for the preparation of 1,1-dichloro-4-methyl-1,3-pentadiene, characterized in that chloral and isobutylene are reacted, then the 1,1,1-trichloro-2-hydroxy-4-methyl obtained -3-pentene of the formula I. OH cl \ I Cl—- CH - CE S C - CH, 'I . ch3 reacted with thionyl chloride without solvent or in an inert solvent and finally the l, l, l, 4-tetrachloro-4-methyl-2-pentene thus obtained to l, l-dichloro-4-methyl-l, 3-pentadiene is reduced. 2. The method according to claim 1, characterized in that the substituted pentene of the formula I is reacted with molar excess of 15-80% used thionyl chloride. 3. Process according to claims 1 and 2, characterized in that the reaction of the substituted pentene with thionyl chloride is carried out in the presence of a catalyst. 4. The method according to claims 1-3, characterized in that the substituted pentene of the formula I in the presence of 1 wt .-% dimethylformamide catalyst with thionyl chloride at a temperature of 40-130 ° C, s advantageous 60-90 ° C, is implemented. 5. The method according to claim 1, characterized in that the reduction of l, l, l, 4-tetrachloro-4-methyl-2-pentene with amalgamated zinc, iron or aluminum powder in alkanol as a solvent at a temperature io of 60 -90 ° C is carried out. 6. The method according to claim 1, characterized in that the reduction of l, l, l, 4-tetrachloro-4-methyl-2-pentene is carried out with basic sodium dithionite. 7. The method according to claim 1, characterized in 15 that the reduction of l, l, l, 4-tetrachloro-4-methyl-2- pentene is carried out catalytically with hydrogen, in acetic acid, in acetone or in alcohol as a solvent at a temperature of 20-60 ° C. 20 8. The method according to claim 7, characterized in that a 5-10% metal-containing carbon-supported palladium catalyst is used in the reduction. 9. The method according to claim 7, characterized in that in the reduction a Raney nickel framework catalyst 25 and organic or inorganic bases - advantageously tri-methylamine or potassium carbonate - can be used.