DE2060083B2 - Process for the preparation of alkynes or their isomeric allenes - Google Patents

Description

R- ¹

R-C == C = -CII-CH-H

R ⁴

H - CH-

C = C-H

O O

I / c

R ¹

R ³

H-C-C = CC-H

dl)

O O

I /

O O

H)

in which R ^{1 is} hydrogen, an alkyl group having 1 to 6 carbon atoms or the group -O-CO-R ⁵ and R ² to R ^{5 are} hydrogen or alkyl groups having 1 to 6 carbon atoms, with the proviso that R ^{2 are the} same Is hydrogen when R ^{1 stands} for an —O — CO — R ⁵ group, or one of their isomeric allenes of the formulas

20th

characterized in that one Formyloxyalkynes of the general formula «ι

R ⁴ R- ¹

I I

HCC = CCR ²

in which R ¹ to R ^{4 have} the meaning given above in the presence of finely divided metals of group Ib and / or cadmium or zinc as metals of group Hb and / or nickel, palladium or platinum as metals of group VIIIb of the periodic table or such compounds These metals, from which the free metals are formed under the reaction conditions, are heated to temperatures of 140 to 260 ° C.

2. The method according to claim 1 for the preparation of an alkyne of the formula III, in which R ^{1 is} -O-COH and R ² - H and R ³ and R ^{4 have} the meaning given in claim 1, as the main product, characterized in that one the reaction is carried out in the liquid phase, diformyloxyalkynes of the formula II

The amount of carbon dioxide that was split off was 40 to 80% of the total carbon dioxide that could be split off amounts to.

3. The method according to claim 1 or 2 for the preparation of an alkyne of the formula III, in which R ^{1 is} -O-COH and R ² - H and R ³ and R "have the meaning given in claim 1, as the main product, characterized in that that the reaction is carried out in the liquid phase, diformyloxyalkynes

R ⁴

R ^J

H-C-C = C-C-H (II)

OO OO

C C

H H

used and the resulting decarboxylation products immediately after distillation from the Reaction mixture removed.

4. The method according to claim 1 for the preparation of an alkyne of the formula IV

R ⁴

R- '

H-C-C = C-C-H

(IV)

H OO

I // c \ ■ r ⁵

in which R ³ and R ^{4 have} the meaning given in claim 1 and R ^{5 stands} for an alkyl group having 1 to 6 carbon atoms, characterized in that formyloxyalkynes of the formula VI

R ⁴ R- '

I I

H-C-C = C-C-H (Vl)

I I

OO OO

c ^y c '

HR ⁵

heated in the presence of the catalysts as defined in claim 1 at temperatures of 140 to 26O ⁰ C.

A characteristic reaction of formic acid esters is catalytic decarbonylation, ie the splitting off of carbon monoxide with the help of alkaline catalysts. Decarboxylation, on the other hand, can only be enforced by applying temperatures of around 300 ° to 400 ° C. Formyloxyverbindungen only that at the carbon atom bearing the formyloxy: bear aryl substituents carries tend already at temperatures below 200 ⁰ C.

for decarboxylation. This makes the application of decarboxylation reactions strong restricted

There has now been a process for the preparation of alkynes of the general formula III

R ⁴

R ³

L- L. = v_ ν- Κ

I I

HR ¹

(HI)

in which R ^{1 is} hydrogen, an alkyl group having 1 to 6 carbon atoms or the group —O — CO — R ⁵ and R ² to R ^{5 are} hydrogen or alkyl groups having 1 to 6 carbon atoms, with the proviso that R ^{2 are the} same Is hydrogen when R ^{1 stands} for an -O-CO-PA group, or of its isomeric allenes of the formulas Va or Vb

R ⁴

R ³

HC = C = CH-CH-H R ⁴ R ³

I I

H-CH-CH = C = C-H

(Va)

(Vb)

an alkyl group having 1 to 6 carbon atoms or the group

found, which is characterized in that formyloxyalkynes of the general formula I.

R ⁴ R ³

/ -ι / ~ « r ~> r *> ο 2 / ii

OO R ¹

in which R ¹ to R ^{4 have} the meaning given above in the presence of finely divided metals of group Ib and / or cadmium or zinc as metals of group Hb and / or nickel, palladium or platinum as metals of group VIIIb of the periodic table or such compounds these metals which under the reaction conditions, the free metals are formed at temperatures of 140-260 ⁰ C heated.

This fact is particularly surprising since it results from the corresponding formyloxyalkanes or alkenes No carbon dioxide can be split off under the reaction conditions mentioned (see also DOS 18 05 403).

As formyloxyalkynes of the formula I.

R ⁴ R ³

HCC = CCR ² (I)

OOR ¹

\
H

those in which R ^{1 is} hydrogen, - O - C

R ⁵

ίο and R ² to R ^{4 are} hydrogen or alkyl groups having 1 to 6, preferably 1 to 4, carbon atoms and R ^{5 is} hydrogen or an alkyl group having 1 to 6, preferably 1 or 2, carbon atoms, where, in the event that R ¹ for the group

—O — c

stands, R ² is hydrogen.

Depending on the type of compound desired as the end product, those of the formula I can be used Alkynyl formates (formyloxyalkynes), alkynediol di-formates (Diformyloxyalkynes) or the monoformates of alkynediols, whose second hydroxyl group is replaced by a other carboxylic acid is esterified, can be used as starting materials. Are alkynes or a mixture from alkynes and the isomeric allenes desired as the end product, alkynyl formates or alkynediol formates can be used be subjected to CO2 separation. The diformates are used to produce alkynyl formates of alkynediols and, for the production of carboxylic acid esters of alkynols, the monoformates of alkynediols, whose second hydroxyl group is esterified by other carboxylic acids, used as starting materials. Since the last-mentioned compounds are difficult to prepare in pure form, can for Production of carboxylic acid esters of alkynols also uses their mixtures with alkynediol formates since the ester mixture obtained can easily be separated by distillation.

The process is particularly important for the splitting off of carbon dioxide from alkynediol formates.

In general, the following formyloxyalkynes of the formula I can be used:

2-penty-1-yl formate,

5-decyne-4,7-diol-di-formate,

4-octyne-3,6-diol diformiate,

2-hexyne-1,4-diol-di-formate,

2-heptyne-1,4-diol diformiate,

5-methyl-2-hexyne-1,4-diol diformiate,

2-heptin-1-yl-formate,

2-octyne-1,4-di-di-formate,

2-octyn-1-yl formate.

In particular, the following are mentioned:

2-3utin-l-yl-formate,

2-butyne-1,4-diol diformate,

2-butyne-1,4-diol monoformate monoacetate,

2-penty-1,4-diol diformiate,

3-hexyn-2-yl formate,

3-hexyne-2,5-diol-di-formate.

For the preparation of the alkynediol diesters of the formula I necessary alkynediols are, for example, by reacting acetylene, propargyl alcohol or 3-alkyl-substituted Easily accessible l-alkyne-3-oils with the corresponding aldehydes.

The alkynyl formates of the formula i, in which R ² and R ¹ are hydrogen, can be prepared from the corresponding alkynediol formates by the process of the present invention.

The Formyloxyalkynes are with finely divided metals uder connections of these metals, which under the reaction conditions are completely or partially converted into the free metals, brought into contact. The metals act as decarboxylation catalysts.

According to the invention, the following catalysts are suitable: The metals of group Ib of the periodic Systems, d. H. Copper, silver and gold, from the metals of group Hb of the periodic table and cadmium Zinc, mixtures of these metals or their alloys such as bronze or brass and compounds these metals, which can form the corresponding metals under the reaction conditions. Furthermore can of the metals of group VIIIb of the periodic table nickel, palladium and platinum, in particular Nickel and palladium or compounds corresponding to the above definition, as decarboxylation catalysts be used. The metals are finely divided, from metal powder to metal grit, or finely distributed on a catalyst carrier material such as pumice stone, silica gel, activated carbon or aluminum oxide, applied.

As compounds of these metals which can be used according to the invention are above all the Called oxides, carbonates, acetates and formates.

However, metals from group Ib of the periodic table, in particular, are preferred as catalysts Copper as well as copper alloys and the compounds of copper as defined. As special cheap catalysts are: copper powder, copper shavings, copper grits, copper (II) oxide, copper carbonate, Copper (II) acetate, copper (II) formate and copper chromite, but also bronze or brass powder or Shavings or semolina. For example, copper acetylacetonate, on the other hand, does not act catalytically within the meaning of the invention, that under the reaction conditions it does not, or only to an insignificant extent, convert into metallic copper is convicted.

The carbon dioxide elimination according to the invention can be carried out in the gas phase, for example by passing formyloxyalkynes of the formula I alone or diluted with an inert gas such as nitrogen, at reaction temperature via a fixed contact.

However, it is particularly advantageous to work in the liquid phase. The formyloxyalkynes can be used here def formula I in pure form, but also dissolved in solvents or emulsified with the catalyst on the Reaction temperature are heated.

The reaction temperature is generally from 140 ° to 26O ⁰ C, preferably 160 ° to 220 ⁰ C. In special cases, but you can also at lower, ie at temperatures above 100 ⁰ C, or higher temperatures work to about 280 ⁰ C.

The reaction time depends on how the reaction is carried out Reaction temperature and the catalyst. It is generally 1 minute to 10 hours.

When working in the gas phase, somewhat higher temperatures, for example up to 280 ^° C., and shorter reaction times, for example 30 seconds to 3 minutes, are generally used.

^r, are Deim work in liquid phase for the preparation of alkynes and allenes reaction times of about 1 to 10, preferably 2 to 6 hours is required for the manufacture of Alkinylestern as the major product, in general, reaction times of a few minutes

κι up to 3 hours. In the case of special procedures, such as the dropwise addition of the formyloxyalkyne I to the suspension of the catalyst heated to the reaction temperature in a high-boiling solvent with simultaneous distilling off of the decarboxylation products, however, the dwell time of the formyloxyalkyne at the contact can also be only a few seconds.

You can split off carbon dioxide at normal pressure, but also at pressures up to 200 atm or else at reduced pressure. The reaction

2Ii can be carried out discontinuously and continuously will.

In principle, those solvents which are not with the reaction conditions come into consideration as solvents react with the starting materials or the catalyst.

2Ί Examples include: benzene, diethylbenzene, Diisopropylbenzene, diphenylmethane, diphenyl, diphenyl oxide, ethers of ethylene glycol and di- or Triethylene glycol with alcohols with up to 4 carbon atoms, as well as triaryl methanes and other aromatic

SO matic special mineral oils or mixtures of these Solvent.

Particularly suitable are high-boiling aromatic oils as diphenylmethane and the boiling at 390 ⁰ C and a mixture of isomeric of Triaryldimethane

s-j existing Marlotherm S® (product of the chemical Werke Hüls AG, Mari), the company's special aromatic mineral oil known as Mobiltherm 600® Mobil Oil AG in Germany, or Diphyl (heating bath liquid consisting of 27% diphenyl and 73%

w diphenyl oxide).

Those formed from formyloxyalkynes of the formula I during the splitting off of carbon dioxide according to the invention Reaction products are processed using customary methods, for example by distillation, if necessary after

■ n gen condensation, worked up.

Depending on the nature of the starting materials and the desired main products, the process according to the invention can be implemented in various ways.
If alkynediol formates of the formula II

R ⁴

R · '

II - (C = C-C-H

I I

ο ο ο ο

When starting compounds are used al ^c , alkynyl formates are formed primarily with elimination of 1 mol of CO ₂ per diformate, which can spy off further carbon dioxide with formation of the corresponding alkynes or a mixture of alkynes and isomeric allenes. In general, allyl esters are formed

of the formulas HIa and / or IHb

R ⁴ R- '

I!

II C CC C- II

I!

O O Il

Il

R ⁴ R- ¹

H- CC CCII

II OO

(purple)

(lllb)

and alkynes of the formula IV
R ⁴

R- '

II -CW-CrC (HH

(IV)

or alkynyl esters of the formulas IHa and HIb, alkynes of Formula IV and isomeric allenes of the formulas Va and Vb

R ⁴

R- '

HCC CW CH-H

R ⁴ R- '

I I

H-CH WC CC Il

(Vn)

(Vb)

side by side. If the substituent R ^{4 of} the alkynediol formates used corresponds to the substituent R ^] , there are of course no isomeric mixtures of alkynyl esters and allenes. Is only one of the substituents R ⁴ or R ^! If the alkynediol formates II is an alkyl group, then that formyloxy group which is bonded to the carbon atom bearing the alkyl group is preferably removed by splitting off carbon dioxide.

If the main products are alkynyl formates from the corresponding alkynediol formates of the formula II produce, so you have to ensure that the main amount of the resulting alkynyl formates cannot wcitcrrcagicren with further elimination of CO ^. One can do this achieve by stopping the reaction if the conversion is incomplete, e.g. B. by lowering the Temperature and isolating the alkynyl formate from the reaction mixture in a known manner, preferably by distillation.

It is beneficial to terminate the reaction when a COj-Mengc has been split off, which is about 40 to 80% of the total CO? amounts to. In this variant of the procedure it is particularly advisable to split off carbon dioxide in the presence of a solvent to undertake.

In many grooves it is possible to disperse the carbon dioxide according to the invention from alkynediol formates Formula II to be carried out in such a way that you (3 Alkynylformiiitc as

Main products are formed by carrying out the reaction in the liquid phase and the resulting decarboxylation products are immediately removed from the reaction mixture by distillation. This process variant is particularly suitable for the continuous production of alkynyl formates. This process variant has proven particularly useful in the preparation of 2-butyn-1-yl formate from 2-butyn-1,4-diol diformate, since 2-butyn-1-yl formate has a boiling point of 138 ° to 140 ⁰ C is easily separable from the 2-butyne-1,4-diol diformate, which only boils at 238 ° C., under the reaction conditions. By transesterification with methanol in the presence of acidic catalysts, 2-butyn-1-ol, which is of great industrial importance and can only be obtained with great difficulty by conventional methods, is easily obtained from 2-butyn-1-yl formate in addition to methyl formate. The homologous alkynols with a hydroxyl group in the α-position to the triple bond can also be prepared analogously.

Distilling Alkinylformiaten with a boiling point above 200 ⁰ C is preferably carried out under reduced pressure.

For the preparation of alkynyl esters of the formula VI

R ⁴

R- '

(VI)

H-CH-C = C-C-H

I. ο ο

I. / c

R ⁵

in which R ^J and R ^{4 are} hydrogen or alkyl groups having 1 to 6, preferably 1 to 4 carbon atoms and R ^{5 is} an alkyl group having 1 to 6, preferably 1 or 2 carbon atoms, the corresponding formyloxyalkynes of the formula VII are used

R ⁴

R- '

II C ^- -C ^ rC-CH (VII)

I I

ο ο ο ο

Il

R- "

in which R 'to R ¹ "have the meaning given in formula VI, that is, from alkynediol monoformic acids whose second hydroxyl group is esterified by the corresponding higher carboxylic acid the esterification of the alkynediols with formic acid and the higher carboxylic acid with alkynediol formates and, after the carbon dioxide has been split off, the alkynol esters formed are separated from one another in the customary manner, for example by fractional distillation.

Used in the elimination of carbon dioxide from alkynediol formates of the formula II, the reaction is not prematurely interrupted or the alkynyl formates formed primarily not removed from the reaction mixture, with elimination of the second mole of carbon

dioxide in general mixtures of the alkynes of the formula IV and allenes of the formulas Va and Vb.

The quantitative ratio between the alkynes formed and the allenes depends on the nature of the substituents R ^J and R ⁴ .

If the formyloxyalkynes of the formula I are used, in which R ^{1 represents} H or the group

Il

and R ² to R ^{4 are} hydrogen, according to the invention, the main product is 2-butyne, which contains only small amounts of 1,2-butadiene.

If, on the other hand, one starts from formyloxyalkanes of the formula I, in which R ¹ and R ^{4 are} methyl and R ^{2 is} hydrogen and R ^{1 is} hydrogen or the group

Il

stands, the main product is hexadiene (2,3), which contains only a little 3-hexyne.

Depending on the reaction conditions, a greater or lesser proportion of the alkyne compounds forms tar-like by-products during heating. The proportion of these tarry by-products can, however, be reduced if the reaction is carried out
Carries out the presence of a solvent.

Since alkynediols and alkynols are formed in an alkaline environment with the reduction of acetylenes and aldehydes decompose and in the starting compounds of formula I still small amounts of unesterified Alkynediol or Alkynol may be included, when working in the liquid phase, the invention Reaction batches usually a small amount of formic acid or a poorly volatile carboxylic acid, in particular added to a dicarboxylic acid. 2-Ethyl-hexanoic acid, palmitic acid, Stearic acid, suberic acid, preferably adipic acid and pimelic acid. These acids are used in the reaction mixture expediently in amounts of 0.05 to 2% by weight, preferably 0.1 to 0.5% by weight, based on formyloxyalkyne added.

With the help of the process according to the invention, the previously available starting materials can be used alkynyl esters of the formula IHa or MIb and Vl as well as Hydrocarbons with a C — C triple bond, such as 2-butyne, or hydrocarbons with 2 adjacent C-C double bonds, such as 2,3-hexadiene, in relatively easy to manufacture.

The compounds prepared according to the invention and those from the alkynyl esters are easy and practical Alkynols that can be prepared in quantitative yields are valuable intermediates for organic syntheses. For example, 2-butyne oil, which can be easily prepared from 2-butyn-1-yl formate, is a valuable intermediate product for the production of 2-butyn-1-al and tetrolic acid as well as for the production of insecticides, especially Acaridia (see for example DOS

19 62 408, DOS 19 50 991 or Swiss patent specification 4 75 708). According to German patent specification 1055492, 2-butyn-1-ol can be used as a corrosion inhibitor. The 2-butyne which can be produced according to the invention is a starting material for the production of trimethylhydroquinone, an intermediate for the production of vitamin E. Alkynyl esters of higher fatty acids can can be used as plant growth substances (see Dutch patent specification 68 14 402).

example 1

The mixture is heated in a 3 liter stirred autoclave Mixture of 1000 g of diphenyl methane, 800 g of 2-butyne-1,4-diol formate (Bp = 238 °) 10 g of copper (II) oxide and 15 g of adipic acid at 190 ° C for 3 hours. A gas chromatic Analysis of the gas and liquid phase of the reaction mixture shows a conversion of 74% below Formation of 54% 2-butyn-1-yl formate and 30% 2-butyne, based on the converted starting material.

Example 2

50 g of 3-hexyne-2,5-dioldiformate are heated in a flask (Bp 0.5 68 °) with 0.5 g of copper (II) oxide to 220 ° C and distilled in the course of about 2 hours Normal pressure while passing nitrogen through the decarboxylation products 3-hexyn-2-yl formate and 3-hexyne in a mixture with 2,3-hexadiene and unreacted starting material. The reaction proceeds with a conversion of 87%. Fractionation of the distillate gives 3-hexyn-2-yl formate (Kp.no 113 ° C) in a yield of 11% and a mixture of 3-hexyne and 2,3-hexadiene (boiling point 81 ° C.) in a yield of 32% of theory, based on the reacted 3-hexyne-2,5-diol diformate.

Example 3

A mixture containing 25% 2-butyne-1,4-diol diformate vapor and 75% nitrogen, is at a pressure of 550 Torr through a 1 m long quartz tube located contact heated to 280 ° C (5% copper (H) oxide on pumice stone chippings with a diameter of 3 to 5 mm). The residence time of the gas on Contact is about 1/2 minute. The vapors emerging from the reaction space are condensed and fractionally distilled. With a conversion of 68.5%, a yield of 36.5% of 2-butyne is obtained (Bp 28 ° C) and 4% 2-butyn-l-yl formate (bp 138 ° bis 140 ° C) based on converted starting material.

Example 4

A mixture of 23.8 g of 2-butyne-1,4-diol-1-formate-4-acetate, 25.6 g of 2-butyne-1,4-diol formate, 0.5 g of cupric oxide and 0.2 g of adipic acid is heated to 250-265 ° C. If one leaves the decarboxylation reaction which occurs resulting lower-boiling liquids continuously from the reaction mixture distill off, in the course of about 3 hours 23.5 g of a mixture of 2-butyn-1-yl acetate are obtained, 2-butyn-1-yl formate and the unreacted starting materials. The yields were determined by gas chromatography Analysis of the mixture determined.

With a conversion of 88%, the yield of 2-butyn-1-yl acetate is 37%, based on the converted 2-butyne-1,4-diol-1-formate-4-acetate.

With a conversion of 86%, the yield of 2-butyn-1-yl formate (boiling point 138 ° to 140 ° C.) is 70%, based on on converted 2-butyne-1,4-diol diformate.

Il

Example 5

A mixture of 50 g of 2-pentyn-l, 4-diol diformate (Kp0.4 73 ° C) and 0.5 g of copper (II) oxide is heated to about 22O ⁰ C. If the products formed during the decarboxylation reaction and small amounts of starting material are allowed to distill off while nitrogen is passed through, 14.1 g of a distillate are obtained in the course of about 3 hours. The reaction proceeds with a conversion of 81%. The yield of 2-pentyn-1-yl formate (bp 69 ° C) is 14% (based on converted starting material).

Example 6

A mixture of 100 g of 2-butyne-1,4-diol diformate, 1.0 g of copper (II) oxide, 0.1 g of adipic acid and 25 g Diphenylmethane is heated in a flask to about 250 ° C and in a gentle stream of nitrogen at 140 ° bis 190 ° C boiling liquid distilled off continuously. In the course of about 3 hours a distillate is obtained from 36,2g2-butyn-1-yl-formate (boiling point 138 ° to 140 ° C) and 21.2 g of starting material can be isolated. At a conversion of 79%, the yield amounts to 2-butyn-1-yl formate 67% (based on converted 2-butyn-1,4-diol diformate).

Example 7

In a round-bottomed flask preheated to 250 ° C, the Contains 0.5 g of copper powder and 0.1 g of adipic acid, 50 g of 2-butyne-1,4-dioldiformate are added dropwise to 3 under nitrogen Hours and the resulting 2-butyn-1-ylformate is distilled together with unreacted starting material. By fractionation under reduced pressure 4.6 g of 2-butyn-1-yl formate and 14.7 g of 2-butyn-1,4-diol diformate can be obtained. The reaction proceeds so with a conversion of 70.6%. The yield of 2-butyn-1-yl formate is 19% (based on Starting material). 2-butyne is not obtained under these reaction conditions.

Example 8

In a 250 ml shaking autoclave, a mixture of 22 g of 2-butyne-1,4-diol diformate, 0.1 g of adipic acid and 1 g of copper (II) O) (id in 100 g of benzene for 6 hours at 220 ° C. The evolution of carbon dioxide leads to an increase in pressure to 65 atmospheres. Distillation of the reaction product gives 21.2 g of an approximately 20% solution of 2-butyne in benzene. 2.3 g of 2-butyne-1, 4-diol diformate remain in the residue. thus the reaction proceeds with a conversion of about 90%. The yield of 2-butyne (Kp. 28 ⁰ C) is 57% based on reacted starting material.

Example 9

A mixture of 100 g of 3-hexyne-2,5-diol diformate, 0.5 g of copper (II) oxide and 0.1 g of adipic acid in 50 g of one is heated at 390 ° C. in a 0.25 liter shaking autoclave boiling aromatic oil from Chemische Werke Hüls AG (Marlotherm S) at 200 ° C. for 6 hours. As a result of the evolution of carbon dioxide, the pressure rises to 40 atmospheres. Fractional distillation of the resulting reaction solution gives 15 g of an isomer mixture consisting of a little 3-hexyne and essentially 2,3-hexadiene with a boiling point of from 81 to 83 ^° C .; 13 g of 3-hexyne-2-yl-formate (Kp.nn 113 ⁰ C) and 27 g of 3-Hcxin-2,5-diol-difomiiat (Kp.no 153 ° to 158 ° C).

The conversion is 73%, the yield of 3-hexyn-2-yl formate 24% and the yield of 2,3-hexadiene, which contains small amounts of 3-hexyne, 43% of theory, based on converted 3-hexyne-2,5-diol diformate.

Example 10

The mixture is heated in an 80 liter stirred autoclave a mixture of 21.4 kg 2-butyne-1,4-diol diformate, 22.5 kg high-boiling aromatic oil (Malotherm S,

κι product of Chemische Werke Huls AG), 110 g of copper powder and hog adipic acid under a nitrogen pressure of 10 atmospheres at temperatures from 195 to 200 ⁰ C. After a reaction time of 80 minutes, a pressure of 115 atm has been established. After cooling down

ΙΊ The pressure vessel is relaxed at room temperature and the mixture obtained is distilled in a column. 0.44 kg of 2-butyne, 7.3 kg of 2-butyn-1-yl formate and 3.8 kg of unreacted 2-butyne-1,4-diol diformate. the The reaction proceeds with a conversion of 82%. the

2 (i the yield of 2-butyne is 7%, that of 2-butyn-1-yl formate 60% of theory, based on converted 2-butyne-1,4-diol diformate.

Example 11

2i Heat in a 1 liter round bottom flask with stirring, a suspension of 15 g of copper (II) oxide and 15 g of adipic acid in 300 g of high-boiling aromatic oil (Marlotherm S, product of the company Chemische Werke Hüls AG) to temperatures of 205 ° to 210 ° C

ίο and 965 g of 2-butyne-1,4-diol diformate are added dropwise within 5 hours to. During the dropwise addition, 588 g of one are in the stream of the carbon dioxide formed Mixture of 2-butyne, 2-butyne-1-yl formate, 2-butyne-1,4-diol diformate and small amounts of side pro-

r> ducts distilled off. Fractional distillation of the distillate obtained gives 25 g of 2-butyne (b.p. 25 ° to 28 ° C.), 319 g of 2-butyn-1-yl formate (Κρ., Οο 80 ° to 81 ° C.) and 173 g of unreacted 2-butyn-1 ₁ 4-diol diformate (Kp ο. ,, 80 ° to 85 ⁰ C).

• κι The reaction thus proceeds with a conversion of 82%. The yield of 2-butyne is 8%, that of 2-butyn-1-yl formate is 58% of theory, based on converted 2-butyne-1,4-diol diformate.

^V) Example 12

In a 250 cc autoclave heated-making a mixture of 50 g of an aromatic oil boiling at 390 ⁰ C (Marlotherm S), 50g of 2-butyn-l-yl-formate, 5g

ίο copper powder and 3 g of adipic acid to 180 ° C. After 6 Hours I have set a pressure of 48 atm. After cooling to room temperature, it is relaxed Pressure vessel and distilled the autoclave discharge at normal pressure. 17 g of a distillate are obtained, which after

■ v> .-% 82Gew gas chromatographic analysis contains (13.9 g) of 2-butyne. With complete conversion of the 2-butyn-1-yl formate, 13.9 g of 2-butyne correspond to a yield of 50% of theory.

^hl) Example 13

In a 500 cc round bottom flask heating a suspension of 6 g of colloidal silver in 150 grams of a 390 ⁰ C boiling Aromatenöls (Marlotherm S) h ¹⁾ at 205 ° to 210 ° C, dropwise with stirring over 6 hours 477 g 2 -Butyne-1,4-diol diformate and the resulting products are distilled off at the same time. Fractional distillation gives 57 g of 2-butyne, 10 g

2-butyn-1-yl formate and 103g 2-butyn-1,4-diol diformate.

The reaction proceeds with a conversion of 78%. The yield of 2-butyne is 40% that of 2-Butyn-1-yl formate 4% of theory, based on converted 2-butyn-1,4-diol diformate.

Example 14

In each case 0.5 g of the metals or metal compounds given below are mixed with 10 g of 2-butyne-1,4-diol diformate heated in the course of about 60 minutes and the temperature at which strong gas evolution occurs, determined. This gas development can be observed:

a) at temperatures of approx. 190 ° to 210 ° C with copper powder, copper (II) oxide, copper (II) formate, Copper (ll) acetate, copper (l!) - carbonal and copper chromite,

b) at temperatures of about 210 ° to 225 ° C with silver oxide, gold (III) chloride, brass powder, cadmium powder and Palladium on charcoal (10%),

c) at Temperatren above 225 ° C and below 238 ⁰ C (Kp. of 2-butyne-l, 4-diol diformate) with nickel powder and zinc powder.

With the help of barite liquor and palladium chloride solution it can be determined that the gas that is developing consists mainly of carbon dioxide in addition to very little carbon monoxide.

Claims (1)

Patent claims: 1. Process for the preparation of alkynes of the general formula R ⁴ R ¹ HCC = CCR ² I. n R ¹