DE1922412B2 - PROCESS FOR THE PREPARATION OF 1-ALKENYL ISOCYANATE - Google Patents

Description

R ¹

(D

in which the individual radicals R ^{1 can be} identical or different and each represent a hydrogen atom, an alkyl, cycloalkyl, aralkyl or aryl radical and, moreover, two radicals R ¹ , provided they do not represent hydrogen atoms, members of a carbocyclic Ringes can denote, while the third radical R ^{1 has} the meaning mentioned, characterized in that N-fl-alkenylJ-N-tert-alkylcarbamic acid chlorides of the general formula II

R ¹

R ¹

* ~ t

R ¹

COX

(II)

The present invention relates to a process for the preparation of 1-alkenyl isocyanates by heating of N-I -alkenyl-N-tert-alkylcarbamic acid chlorides.

It is known that 1-alkenyl isocyanates are produced by Curtius degradation of azides, α, / ϊ-unsaturated carboxylic acids (cf., for example, Journal of Organic Chemistry, Volume 26 [1961], pages 770 to 779 and Volume 27 [1962], pages 1454 and 1455, Chemical Reports, Volume 98 [1965], pages 650 to 652 and Bull. Soc. Chim. BeIg., Volume 65 [1956], page 291). Despite the interest that 1-alkenyl isocyanates are valuable monomers or have found comonomers for the production of polymeric substances (cf. the first-mentioned reference), was the process mentioned because of the ready decomposition of the azides and because of the explosion hazards associated with their handling are not exercised on a technical scale (cf.Houben-Weyl, Methods of Organic Chemistry, Volume 8 [1952], pp. 124-125, and US Patent 23 34 476).

It has now been found that 1-alkenyl isocyanates of the general formula I

R ¹

(D

can be and each represent a hydrogen atom, an alkyl, cycloalkyl, aralkyl or aryl radical and, in addition, two radicals R ¹ , unless they are hydrogen atoms, can denote members of a carbocyclic ring, while the third radical R ¹ has the meaning mentioned, can be produced in a simple manner if N- (I-alkenylJ-N-tert-alkylcarbamic acid chlorides of the general formula II

in which R ^{1 has} the meaning given and R ^{2 is} a tert-alkyl group and X is a halogen atom, thermally cleavage.

2. The method according to claim 1, characterized in that the thermal cleavage in The presence of metal compounds.

C = C-N = C = O

/ I

R ¹ R ¹

in which the individual radicals R ^{1 are} identical or different to R ¹

C = CNR ²

R ¹ R ¹ COX

(M)

in which R ^{1 has} the meaning given and R- is a tert-alkyl group and X is a halogen atom, thermally cleavage.

According to the process, 1-alkenyl isocyanates can be safely converted into good to excellent Yields are produced. Particularly good yields are obtained if the starting materials 11 in Thermally cleaves the presence of metal compounds.

The N- (l-alkenyl) -N-tert-alkylcarbamic acid chlorides used as starting materials can, for example, by reacting phosgene with appropriate Schiff bases according to the DT-OS method 19 01 542 can be obtained.

Preferred starting materials II and correspondingly preferred end products I are those in whose formulas the individual radicals R ^{1 can be the} same or different and are each a hydrogen atom, an alkyl radical, in particular with 1 to 20, preferably 1 to 8 carbon atoms, a cycloalkyl radical, in particular with 5 up to 12, preferably 5 to 8 carbon atoms, an aralkyl radical, in particular with 7 to 12 carbon atoms or an aryl radical with a maximum of 12 carbon atoms and, in addition, two radicals R ¹ , if they do not mean hydrogen atoms, members of a 5- to 12-membered group , in particular 5- to 8-membered, carbocyclic ring, while the third radical R ^{1 has} the meaning mentioned. ^{Two radicals R 1} located on two different carbon atoms can also denote members of a polycycloalkyl radical, in particular a bicycloalkyl radical having 7 to 10 carbon atoms or a tricycloalkyl radical having 7 to 12 carbon atoms. Preferred tert-alkyl groups R ² contain 4 to 10, in particular 4 to 6, carbon atoms ^ The radicals mentioned can also be replaced by groups and / or atoms which are inert under the reaction conditions, e.g. B. chlorine atoms, bromine atoms, trifluoroalkyl, alkoxy, alkylthio, alkylsulfonyl groups, each with 1 to 4 carbon atoms, nitro groups, phenoxy groups, may be substituted. In the preferred starting materials II, X denotes an iodine atom, a bromine atom and in particular a chlorine atom.
Suitable starting materials II are, for example

N-vinyl-N-tert-butyl-, N-vinyl-N-tert-amyl-,

N-1 -propenyl-N-tert.-butyl-,

N-2-propenyl-N-tert.-butyl-,

N-1-butenyl-N-tert-butyl-,

N-I-methyl-1-propenyl-N-tert.-butyl-,

N-2-methyl-1-propenyl-N-tert.-butyl-,

N-l-ethyl-l-hexenyl-N-tert.-butyl-,

N-l-Cyclohexenyl-N-tert-butyl-,

N-l-Cyclooctenyl-N-tert.-butyl-,

N-1-cyclopentenyl-N-tert.-butyl-,

N-2-phenyl-vinyl-N-tert.-butyi-carbamic acid

chloride. ■ -,

To prepare the 1 -Alkenylisocyanate I the starting materials Il generally at temperatures between 20 and 300 ⁰ C are heated, wherein the 1-alkenyl isocyanate κι by elimination of tert-alkyl halide or its Dehydrohalogenierungsprodukt and hydrogen halide formed. The starting material II can be brought to the reaction temperature in the liquid or gaseous state.

When working in the liquid phase, the starting material can be thermally cleaved as such or in the presence of an inert π diluent. In general, _{however, the starting I} offc are thermally cleaved in the absence of diluents.

For the implementation of the starting material in gaseous jo The starting material, which is usually liquid, must like a state before thermal cracking into the gaseous state State to be transferred. The conversion into the gaseous state can for example be done by working under reduced pressure or by passing through an inert gas, for example nitrogen or Carbon dioxide, can be achieved through the liquid starting material.

The reaction is generally carried out at atmospheric pressure. However, it is also possible to carry out the cleavage at elevated pressure, for example 3 at, or under reduced pressure, for. B. 300 Torr to perform. A preferred embodiment of the process consists in cleaving the starting materials II in the presence of metal compounds, in particular π metal salts, as catalysts. When the reaction is carried out in the presence of the metal compounds mentioned, the reaction temperature is greatly reduced and, at the same time, the yield of 1-alkenyl isocyanate is increased. While, applying in the absence of said preferably in metal compounds, reaction temperatures between 100 and 250 ° C, in particular 130 and 200 ° C, the reaction is carried out in the presence of said metal compounds, preferably at temperatures of 30-160 ⁰ C, -r, in particular 30 and 120 ⁰ C, from. In the case of the catalytic thermal cleavage of, for example, N-Vmyl-N-tert-butylcarbamic acid chloride, an equimolecular mixture of vinyl isocyanate and tert-butyl chloride is obtained in almost quantitative yield. In contrast, lower yields of vinyl isocyanate and tert-butyl chloride are achieved in the uncatalyzed thermal cleavage, with isobutylene, phosgene and hydrogen chloride being formed as by-products.

Preferably compounds of the metals of τ, Groups 3a, 4a, 5a and 7b and the transition elements of the periodic table are used for characterization the groups that z. B. in Handbook of Chemistry and Physics, 4 &. Edition (1968-1969) to be based on the specified group designation t> o is. The catalysts can be organic or inorganic metal compounds. Advantageous Metal salts are used, the type of anion in the metal salts not being critical. Suitable metal compounds are, for example, lead (II) chloride, antimony (III) chloride, copper chloride, Copper (II) chloride, cadmium (II) phosphate, mercury II) chloride, bromide, sulfate, acetate, chromium (III) chloride, Manganese (II) chloride, palladium (II) chloride, bismuth (III) chloride, zinc chloride, zinc cyanide. The amount of catalyst can vary within wide limits. In general, the catalyst is used in quantities from 0.1 to 100% by weight, in particular from 1 to 20% by weight, based on the starting material. Bigger ones However, amounts of catalyst, for example of 200% by weight, are not harmful. The catalyst can be used as such or after application to an inert carrier such as aluminum oxide, silica gel, activated carbon, be used. If the catalyst is used as it is, it is preferably made finer Distribution used.

The process according to the invention can be carried out batchwise or continuously.

The process can, for example, be carried out in such a way that all of the starting material II, optionally in the presence of the catalyst, is heated to reaction temperature in a vessel with stirring and the 1-alkenyl isocyanate and / or tert-alkyl halide formed is distilled off via a column. But you can also pass the starting material in liquid or gaseous form through a heated and optionally the catalyst containing tube and then work up the reaction product obtained, for. B. by rectification. In order to facilitate the separation of the 1-Alkenylisocyanaie from the reaction product by distillation, preference is given to choosing those starting substances which provide a 1-alkenyl isocyanate and tert-alkyl chloride whose boiling points are significantly different, e.g. B. by more than 10 ⁰ C differ. If the 1-alkenyl isocyanate has a lower boiling point than the associated tert-alkyl halide, the 1-alkenyl isocyanate can be distilled from the reaction mixture alone. Preferably, however, both reaction products will be distilled off from the reaction mixture because this increases the rate of the reaction.

The I-alkenyl isocyanates are valuable monomers or comonomers for the production of polymers Fabrics.

The parts mentioned in the examples are parts by weight.

example 1

In a stirred vessel with an attached column (about 3 to 6 theoretical plates), 162 parts of N-vinyl-N-tert-butylcarbamic acid chloride are mixed with 20 parts of anhydrous, powdered zinc chloride and heated with stirring. In a Innentemperalur of about 70 ⁰ C the column, a mixture of vinyl isocyanate and tert-butyl chloride begins to distill overhead, while the temperature in the stirred vessel drops to 50 to 60 ⁰ C. The cleavage is over after one hour. 158 parts of an equimolecular mixture of vinyl isocyanate and tert-butyl chloride are obtained. This mixture can be used directly for the preparation of a number of reaction products of the vinyl isocyanate. To obtain the pure vinyl isocyanal, the mixture is subjected to fractional distillation through an effective column. This gives 65 parts (94% of theory) of pure vinyl isocyanate with a boiling point of 37 ° C. as the 1st fraction, and 87 parts of tert-butyl chloride with a boiling point of 51 ° C. as the 2nd fraction.

Example 2

The procedure described in Example 1 is followed, with only 20 parts of zinc chloride by 10 parts each

one of the in the first column of the table below listed metal salts is replaced. The second column of the table shows the reaction temperature in which third column the amount of distillate up to a transition temperature of 760 Torr of a maximum of 52 "C and in the fourth column the yield obtained after fractional distillation of the first distillate Vinyl isocyanate indicated.

McX _n C ¹ Parts % a. Th. PbCI ₂ 114 125 61 SbCI ₃ 48 129 73 CuCl 77 134 79 CuCl ₂ 73 148 89 Cd ₃ (PO ₄ ), 76 122 72 HgCi ₂ 46 158 95 HgBr ₂ 46 156 94 HgSO ₄ 58 146 88 CrCI ₁ 119 115 55 MnCl ₂ 70 149 90 PdCl, 58 159 96 Example 3

50 parts of N-vinyl-N-tert-butylcarbamic acid chloride are together with 20 parts of bismuth (III) chloride in a stirred apparatus with an attached column Stirring heated. After the cleavage has started at an internal temperature of 46 ° C, there are one more starting substance to the same extent as overhead of the column at a transition temperature from 40 to 42 ° C, the mixture of vinyl isocyanate and tert-butyl chloride is distilled off. From a total of 486 parts N-vinyl-N-tert-butylcarbamic acid chloride is obtained thus 472 parts (97% of theory) of an equimolar mixture of vinyl isocyanate and tert-butyl chloride.

Example 4

The procedure described in Example 1 is followed, using 150 parts of N-2-methylpropen-1-yl-N-tert-butylcarbamic acid chloride instead of the N-vinyl-N-tert-butylcarbamic acid chloride and 5 parts of zinc chloride as the catalyst. The cleavage starts at 70 "C. Because of the higher boiling point of the Spallprodukte it is necessary to increase the temperature in the stirred vessel gegnn end of the cleavage at 120 to 130 ⁰ C. The distillate obtained 140 parts of a äquirnolekularen mixture of 2-methyl-propene -i-yl isocyanate and tert-butyl chloride have a boiling point of 49 ° to 107 ° C. The mixture can easily be separated into its constituent parts by fractional distillation, producing 65 parts of tert-butyl chloride and 70 parts (91% of theory ) 2-methylpropen-1-yl isocyanate with a boiling point of 74 ° C. at 260 torr was obtained.

Example 5

100 parts of N-vinyl-N-tert-butylcarbamic acid chloride are heated with stirring in a stirred vessel with an attached column. At an internal temperature of 14O ⁰ C in the course of one hour to distill 74

2 (i parts of reaction products in the boiling range of 34 - 71 ° C above. From the distillate, fractional distillation using a highly effective column in addition to 29 Parts of tert-butyl chloride 20 parts of vinyl isocyanate, corresponding to a yield of 46% of theory

') to win.

Example 6

80 parts of N-vinyl-N-lerl.-butylcarbamic acid chloride are mixed in the cold with 15 parts of anhydrous, powdered zinc cyanide with stirring and then heated with continued stirring. At 80 ⁰ C, the thermal cleavage of the carbamic acid chloride begins, and at the same time cntwikkelt cyanide. The temperature inside the flask falls off quickly at 50 ⁰ C and above the head of an attached column is distilled a equimolecular mixture of vinyl isocyanate and tert-butyl chloride from. A total of a further 730 parts of carbamic acid chloride are added dropwise at the rate at which the cleavage products are distilled off. 769 parts of distillate with a bp 39-45 ° C. are obtained which, according to NMR analysis, contains 50 mol percent vinyl isocyanate in addition to 48 mol percent tert-butyl chloride and 2 mol percent isobutylene, corresponding to a vinyl isocyanate yield of 95% of theory.

Claims (1)

Patent claims: 1. Process for the preparation of 1 - alkenyl isocyanates the general formula I. R ' R ¹ NCO