DE1768860A1 - Process for the production of monofunctional and polyfunctional derivatives of carbonic acid - Google Patents

Description

FARBENFABRIKEN BAYER AG ¹⁷⁶⁸⁸⁶ °

LEVBRKU S E H Beyenmk Pttent Dept.

Process for the production of monofunctional and polyfunctional Derivatives of carbonic acid

i
It has long been known that carbamic acid esters of the general formula (I) ₁

Y
R-NH-GZR »(I)

wherein Y and Z is oxygen or sulfur, and R and R 'mean a solvent inert to isocyanates or isothiocyanates organic radical, thermally with the release of isocyanates or isothiocyanates can be split, for which, however, are necessary temperatures between 150 and 300 G ^0. However, these high temperatures very often cause undesirable side reactions which can be of such magnitude that very little or no isocyanate or ieothiocyanate can be isolated. This applies in particular to those cases in which the isocyanate or isothiocyanate formed is either thermally unstable or else particularly reactive, for example due to the presence of functional groups. It is also known that carbamic acid halides of the general formula (I), in which ZR ^{1 is} halogen, are also used to form isocyanates or isothiocyanates with elimination of hydrogen halide. The necessary temperatures are between about 50 and 15O ⁰ C, somewhat lower than in the carbamic. In spite of this, a considerable amount of side reactions occur here too, not least because of the extremely aggressive one that is released

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Documents iah. 711 at », 2 no? sa-z 2 w "rv * $"& t * *

Hydrohalic acid. In contrast, it is known that the thermal decomposition of carbamic anhydrides !! of the general formula (II),

0 0

Ii i

H-NH-COC-OR ¹ (II)

where R and R * have the above meaning, in no case isocyanates, but always mixtures of other products, e.g. Urea and carboxamide derivatives.

There has now been a process for the preparation of mono- and polyfunctional derivatives of carbonic acid of the general formula (III)

YR ₁ - (N = C) _n found,. (III)

where η stands for <$ anze numbers from 1 to 3, Y stands for oxygen or sulfur and R _{1 stands} for an organic radical which is inert towards isocyanates or Ieothiocyana- 'te, which can also contain functional groups, functional groups with acidic hydrogen atoms are present in silylated form, which is characterized in that N-silylated carbamic acid derivatives of the general formula (IY)

Y -

H ₁ (H- £ Z-Rg) _n . (IV)

R ₃ -Si-R ₅

^R 4

in which n, Y and R _{1 have} the above meanings, R _{2 represents} an optionally substituted organic radical which is inert to isocyanates or isothiocyanates, Z represents oxygen or sulfur; fei or ZR ₂ for halogen and R ,, R ₄ and R ₅ for a lower alkyl, cycloalkyl, aryl, lower alkoxy, cycloalkoxy,

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Aroxy, acyloxy or siloxanyl radical or halogen or hydrogen, ie temperatures between about -20 ° C. and about 200 ^° C., preferably between about 0 and about 130 ^° C., cleaves.

The radicals R ₁ and Rp are preferably an aliphatic, aromatic or heterocyclic radical which is also characterized by one or more identical or different functional groups, for example unsaturated groups, unsaturated ester groups, ester, nitrile, nitro, ether, keto -, ketal or acetal groups can be substituted. The radical R ₁ can also contain functional HO, HS or HOOG groups, which, however, are present in silylated form and must therefore be protected against attack by isocyanate or isothiocyanate groups.

As halogens (Z, Rp), in addition to bromine and fluorine, chlorine is preferably used called. The radicals R *, R. and Re are preferably lower Alkyl residues, 5 or 6-membered cyclo residues, aryl residues with bit to 10 carbon atoms in the ring system (preferably phenyl) lower alkoxy, cycloalkoxy radicals with preferably 5 or 6 Carbon atoms in the ring system as well as aroxy residues (preferably phenoxy), acyloxy residues (preferably residues of a lower aliphatic carboxylic acid and an aromatic carboxylic acid, e.g. benzene acid, phenyleoteric acid). Siloxanyl residues Bind those of the formula O-Si (M alkyl) ,.

As reagents R ₁ are to be understood as meaning aliphatic radicals with up to 20, preferably 1-12 carbon atoms, which can be straight-chain or branched and optionally contain a maximum of two double bonds or one triple bond.

The term aliphatic radicals can of course also be used for cycloaliphatic radicals with 3 to 12, preferably with 5-6 or 7 »carbon atoms in the ring, this being in the case of the 12-ring system up to 3» in the case of the lower cyclo-

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aliphatic radicals * preferably a double bond in the ring contains.

Aromatic radicals R ₁ and R ₂ are those with up to 12 carbon atoms in the aromatic systems, in the case of the preferred phenyl radicals, also 2 of these radicals directly or through oxygen, sulfur, CH ₀ or lower bifunctional, aliphatic or through an N radical -Lower alkyl can be linked.

Heterocyclic radicals are preferably those with 5 to 7 ring members, the heterocyclic ring system optionally also fused to an aromatic radical, preferably a benzene radical. Preferred heteroatoms (maximum 3) are Called oxygen, nitrogen and sulfur. !

The abovementioned groups are suitable as unsaturated groups. Unsaturated ester groups are preferably to be understood as meaning those of unsaturated aliphatic alcohols with up to two double or one broad bond *. Ester groups are to be understood as meaning those corresponding to the radicals described for R 1, R 1 and R c. Ketals and acetals are preferred based on lower aliphatic or cycloaliphatic ketones and alcohols.

The process according to the invention has a number of decisive advantages over the previously known thermal cleavage methods. First of all, the temperatures required for the cleavage of the N-silylated carbamic acid or thiocarbamic acid derivatives are all by themselves significantly lower; in many cases, quantitative cleavage takes place even at room temperature or a little below or above, and the corresponding isocyanates or isothiocyanates can be obtained in excellent form Isolate yields. In the previous processes, the thermal cleavage of urea

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Thanes or thiurethanes, in addition to the isocyanates or isothiocyanates, also the underlying alcohols or phenols, which are known to react with the released isocyanates or isothiocyanates in a temperature range only slightly below the cleavage temperature, with regression of the urethanes or thio * urethanes, which is considerable Reduction of the yield has the consequence. In contrast, in the process according to the invention, instead of the alcohols or phenols, only the silylated derivatives (R ₂ -Z-Si-B ^ R, Rc) are split off, which under the reaction conditions are not capable of any reverse reaction with the isocyanates or isothiocyanates Both factors are of essential importance for the high yields that can be achieved with the method according to the invention. Even with the use of silylated carbamic acid halogens, the cleavage temperature is lowered quite significantly, in the case of carbamic acid chlorides, for example, to below O ⁰ G. ' A significant advantage also results from the fact that the particularly aggressive hydrohalic acids are not split off here, but halosilanes (Hal-SiR, RJR, -) This fact is of decisive importance if either acid-sensitive radicals R ₁ are present or unsaturated groups, to which hydrogen halide acids attach, but not halosilanes. Finally, the cleavage of mixed anhydrides of carbamic acid after silylation of the N-position proton also leads to isocyanates in high yields ^{at temperatures around 0 ° C.}

This cleavage reaction takes place both in the silylated Urethanes and thiourethanes as well as carbamic acid halides and mixed anhydrides of carbamic acid quickly and quantitatively and one isolates in addition to the corresponding isocyanates or isothiocyanates also the silicon-containing cleavage products in high yields of around 80 to 90 #. The one for the present Process starting compounds which are used are known or obtainable by known processes.

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Another advantage of the present process is that, due to the low cleavage temperature, it is possible to isolate ItO cyanates and isothiocyanates with sensitive functional groups that cannot be prepared using the previous thermal cleavage methods , such as β * Β · allyl · ' isocyanate, vinjl isocyanate and β-isocyanatocrotonic acid esters. Also, bi- and tri-functional isocyanates and isothiocyanates are accessible by this process, in particular also those which can not be produced by phosgenation, such as the 1,2-Äthylendiisocyanat. In addition , the process according to the invention also allows the synthesis of interesting and valuable isocyanates or isothiocyanates which have one, several identical or different functional HO, HS or HOOC groups protected by a silyl radical . For this purpose, it is preferable to from the corresponding amino alcohols, Aminothio alcohols, aliphatic or aromatic aminocarboxylic acids Arainophenolen or out, whereby it does not matter in which distance, ie the position in which the amino group is below the walls ren functional groups. According to the invention, amines with several identical or different functional groups, such as, for example, aminodiols, aminosugars, aminodiphenols, aminodimercaptans, aminod / carboxylic acids or aminosalicylic acid and aminothiosalicylic acid, can also be used. The introduction of the silyl protective groups is particularly simple and can be carried out without an additional reaction step, since all existing HO, HS or HOOC groups of an amine or a carbamic acid derivative are automatically and quantitatively co-silylated during the SiIyIation of the Η proton , if only the necessary ones are silylated Amount of silylating agent used. The silylated functional groups are inert to the isocyanate or isothiocyanate groups formed in the cleavage reaction, so that the corresponding derivatives can be isolated in pure form and in high yields. Such isocyanates with blocked hydroxyl, sulfhydryl or carboxyl groups can be used in all typical isocyanate reactions, the protective groups after the isocyanate or isocyanate groups have reacted

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} 1769860

thiocyanate groups very gently by simply treating with Water or alcohol can be split off again so that the HO, HS or HOOC groups are available for further reactions stand. Isocyanates or isothiocyanates of this kind enable the synthesis of a number of novel compounds in an easy way. /

An isolation of the silylated carbamic acid or thiocarbamic acid derivatives ist.for the method according to the invention not necessary and in most cases not appropriate, because the one-pot process - in which one is without isolation of silylated intermediates directly from the carbamic acid or thiocarbamic acid derivative or, even more simply, from the amine comes to the corresponding isocyanate or isothiocyanate - is very easy to carry out and gives high yields. An isolation the silylated carbamic acid or thiocarbamic acid derivatives is also in very many cases under mild Conditions difficult or impossible because they often form rapidly at room temperature or below Isocyanates or isothiocyanates are split. In some cases the silylated carbamic acid or thiocarbamic acid derivatives are respectively but so stable that they can be isolated and cleaved in a second reaction step at a higher temperature can. In these cases too, however, it is possible, if appropriate, to dispense with the isolation and the preparation of the silylated ones Carbamic acid or thiocarbamic acid derivatives and their cleavage in one reaction step as a one-pot process.

As expected, the cleavage of the silylated carbamic acid or thiocarbamic acid derivatives takes place at lower temperatures, the more acidic the compound HZ-Rp, where Z and Rp have the meaning given in the general formula (IV). For example, the p-nitrophenyl ester of N-Trimethyl3ilycarbanilsäure already at 0 to 20 ⁰ C, the p-chlorophenyl ester in 60.bis 70 ⁰ C, the phenyl esters at 100 to 110 ⁰ C.

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and the ethyl ester eret at 130 - HO ⁰ C in phenyl isocyanate and cleaved the corresponding trimethylsilane derivative. In accordance with this, the cleavage of τοη carboxylic acid silyl esters or halosilanes from silylated carbamic acid anhydrides or carbainyl halides takes place already below O ⁰ C. It is therefore in hand, through a suitable choice of the Rg-Z radical, the cleavage of the carbamic acid or thiocarbamic acid derivatives and thus the Allow the formation of isocyanates or isothiocyanates to take place within defined temperature ranges between 0 and 130 C. This possibility is particularly valuable for the use of the silylated carbamic acid derivatives which can be prepared according to the invention as blocked isocyanates; d, they enn allow for the first time, isocyanate or isothiocyanate at certain temperatures in the special interessanten- so far not accessible - temperature range from 0 to 13O ⁰ C to set at liberty.

If appropriate, the simplest way to carry out the process according to the invention is to start directly from the amine which one wants to convert into the isocyanate or isothiocyanate. This amine is then used in a one-pot process without isolation of intermediate products initially converted into a carbamic acid or thiocarbamic acid derivative in a known manner, for example with the help of an organic carbonate, e.g. diphenyl carbonate. The carbamic acid or thiocarbamic acid derivative is then silylated on nitrogen and thermally to the isocyanate by setting the necessary decomposition temperature or isothiocyanate and the corresponding silane derivative split. Likewise, the silylation can already be carried out at the temperature required for the cleavage of the silylated carbamic acid or thiocarbamic acid derivative is sufficient

However, the reaction sequence can also be interchanged. And initially silylate the amine, then acylate, silylate the resulting carbamic acid or thiocarbamic acid derivative and columns. This is particularly advantageous in such cases

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which the amine - such as an aminocarboxylic acid - in proton-free Solvents -very sparingly soluble or insoluble and therefore is also difficult or impossible to acylate. The silylation however, always runs smoothly and the silylated product is in any case very soluble. If one then conducts the aaylation, of the siliconized amines, for example with the help of a chloroic acid ester - e.g. phenyl chloroformate - then chlorosilane is split off first, which after the addition of at least the stoichiometric amount of a tertiary amine directly to Silylation of the N-position proton can be used. So you arrive with the same amount after both methods Silylating agent. For cleavage, the reaction mixture is simply brought to the decomposition temperature and the resulting Isocyanate or isothiocyanate, e.g. by distilling off isolated in pure form. This route is particularly suitable for those amines that contain additional HO, HS or HOOC groups This is because these functional groups are automatically silylated as well during the silylation of the amino group can thus be protected.

The silylation of the carbamic acid or thiocarbamic acid derivatives is most easily carried out by reaction with at least the stoichiometric amount, but optionally also with an excess of a halosilane or halosiloxane in Presence of preferably stoichiometric amounts of one tertiary amine as an acceptor for the released hydrohalic acid. As a halosilane one uses in the simplest way Pail silicon tetrachloride, which due to its 4 silicon-based Chlorine atoms are very economical and also very cheap. According to the invention, however, all other mono-, di- and trifunctional halosilane derivatives are used in which the remaining valences of the Si atom by the same or various substituents are also saturated. Particularly alkoxy, cycloalkoxy, aroxy, Acyloxy, alkyl, cycloalkyl or aryl groups and halogen or hydrogen are possible. For the choice of the halosilane is

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ea is important that the cleavage of the silylated with it Carbamic acid or thiocarbamic acid derivatives resulting silane derivative far enough from the boiling point of the isocyanate or Thioisocyanate derivative is removed, otherwise a distillative Separation is difficult. In some cases, ea can also be advantageous, with the help of a higher molecular weight To silylate halosiloxana, as this is the case with the ■ cleavage The siloxane derivative that forms is no longer volatile, so that the separation of high-boiling isothiocyanate or isothiocyanate derivatives as well is particularly easy. Pur the silylation of Amines or carbamic acid or thiocarbamic acid derivatives which additionally contain HO, HS or HOOC groups, are suitable Triorganohalosilanes are particularly suitable as silylating agents. At the same time as the silylation on nitrogen, the functional groups with triorganosilyl groups are grounded Protected, due to their three, thermo- and hydrolysis-stable Si-C bonds in the subsequent cleavage reactions cannot enter into any undesired side reactions. Instead of complexes of halosilanes and tertiary According to the invention, amines can also use the other known silylating agents, such as silazanes or singly or doubly silylated acid amides can be used.

The thermal cleavage of the N-silylated carbamic acid resp. Thiocarbamic acid derivatives can be inert under the reaction conditions either without a solvent or in the presence of organic solvents. If you go with the invention Process, however, from Amiη, which in a one-pot reaction directly into the isocyanate 'or isothiocyanate is transferred, then it is expedient to work in Presence of organic solvents which are inert under the reaction conditions, such as open-chain or cyclic solvents Ethers, aliphatic or aromatic hydrocarbons or halogenated hydrocarbons, for example in diethyl ether, tetrahydrofuran, Methylene chloride, chloroform, benzene, toluene, xylene or o-dichlorobenzene.

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The isocyanates and isothiocyanates which can be prepared according to the invention are valuable intermediate products for the production of pesticides, laol raw materials and polymers.

example 1

36 g (0.15 M) of carbanilic acid benzoic anhydride are dissolved in 400 ml of dry THP and sllylated while cooling with ice by adding 20 ml (0.15 M) of trimethylchlorosilane and 21 ml (0.15 M) of triethylamine. . After 20 min, the deposited triethylamine hydrochloride (100 # of theory) filtered, evaporated in FiItrat the solvent at an internal temperature of 0 10 ⁰ C, and the residue on a column of distilled · case go at 60-65 ⁰ C / 15 Torr 14g phenyl isocyanate (78% of theory) and at 54-56 ⁰ C / 0.7 Torr Benzoesäuretrimethylsiljlester 24 g (82.5 $ of theory) of about.

Example 2

24 g (0.10 M) carbanilic acid benzoic anhydride are dissolved in approx. 100 ml dry THF and a solution of 14 g (> 0.10 M) N-trimethylsilylacetamide in 50 ml THF is added at room temperature. After the reaction solution has been concentrated to approx. 50 ml, 200 ml of dry petroleum ether are added while cooling with ice. After 15 minutes, the precipitated acetamide (about 96 liters of theory) is filtered off and the filtrate is fractionated over a column after the solvents have been stripped off. Thereby distill at 60-65 ° C / 15 torr 8 g (67 $> of theory) of phenyl isocyanate and 54 to 56 ⁰ C / 0.7 Torr 18 g (93 1 »of theory) benzoic acid trime thylsilyle s ter.

Example 3

129 g (0.6 M) of the by reacting ethanolamine with bis-p-chlorophenyl carbonate urethane obtained (melting point 115 ° -117 °) in 1.5 1 dry THF with 84 ml (0.6 M) triethylamine and

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82 ml (0 * 6 M) trimethylchlorosilane were stirred at room temperature for about 30 minutes and then filtered from the hydrochloride. Ea is washed with 250 ml of THF, the combined filtrates are mixed with 95 ml (0.7 M) of trimethylchlorosilane and 98 ml of triethylamine (0.7 M) and heated to the boil for 16 hours. Mach cooling, it is filtered off from the hydrochloride, washed with 250 ml of THP dae Piltrat fractionated on a column · At 55-56 ⁰ C / 14 mm 71 g '(74 $ of theory) fl-Ieo-

25 '

obtained cyanatoethoxytrimethylsilane, n ~ «1.4160

analysis ber .: G 45 , 25 H 8th , 23 gef.i C. 45 , 53 H 8th , 45 example 4th

226 g (0.8 M) of bis-p-Chlorphenylcarbonat- are placed in 800 ml THF, 48.8 g (0.8 M) ethanolamine added dropwise and the solution after completion of dropwise addition heated to boiling for as long as the pH bie is approximately neutral (pH 8-7). The solution is diluted to approx. 4.2 l with dry THF, 365 ml (2.7 M) trimethylchlorosilane and 378 ml (2.7 M) triethylamine are added, the mixture is heated to boiling for 16 hours, the hydrochloride is filtered off after cooling and with approx Washed out 500 ml of THF. The filtrate is distilled through a column, 80 g (63 % of theory) of p-isocyanatoethoxytrimethylsilane being obtained.

Example 5

To a solution of 220 g (0.8 M) of N-trimethylsilyl * aminocaproic acid trimethylsilyl ester (b.p. 75-80 ⁰ C / 0.001 Torr |.. N ^{2 0} = 1.4349) in 1200 ml of dry toluene at - 10 ^° C. 125 g (0.8 M) phenyl chloroaraeic acid were added, after the addition was complete, the mixture was ^{stirred at 25 °} C. for a further 30 minutes and 21.5 g (0 _s 2 M) trimethylchlorosilane were added. The reaction solution is heated mim boiling added as quickly as possible with 101 g (1 M) Tr-iäthylamin and heated for 3 hours under reflux.

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After cooling, the precipitated triethylamine hydrochloride is filtered off and the piltrate is fractionated over a heatable column. 126 g (69 # of theory) of 82 ⁰ C / 0.6 mm were £ -Isocyanatocypronsäuretrimethylsilylester - 80

η ²⁰ - 1 C. 4385 • H ο, 35 ber. ί G 52, 37 H 8th, 32 found: 52, 31

This isocyanate is also obtained in comparable yields in a one-pot reaction. Here, 131 g of (1 M) ε-aminocaproic acid in 1 liter of dry methylene chloride are added 240 g (2.2 M) trimethylchlorosilane and 250 g (2.3M) triethylamine were added, the mixture was heated to the boil for 4 hours and after cooling to room temperature, the precipitated triethylamine hydrochloride is filtered off. The piltrat will then after the methylene chloride has been stripped off, reacted with phenyl chloroformate and triethylamine in the manner described above and worked up.

Example 6

14-9 g (0.7 M) phenyl carbanil ester are heated to boiling with 101 g (1 M) triethylamine in 1.2 l of dry toluene. While stirring vigorously, 30 g (0.175 M) silicon tetrachloride are added as quickly as possible, triethylamine hydrochloride immediately separating out in an exothermic reaction. The reaction solution is heated to boiling for a further 2-3 hours, after cooling the triethylamine hydrochloride is filtered off and the piltrate is distilled. In this case, 66.5 g (80% of theory) of phenyl isocyanate pass over and 65 g (93 % of theory) of crystalline tetraphenoxysilane remain as the residue.

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Example 7 ■ * ^

194 g (0.5 M) phenyl thiocarbanilate are heated ^{to 100 °} C. together with 56 g (0.55 M) triethylarain in approx. 800 ml toluene. To this end, 21.5 g (0.125 M) silicon tetrachloride are added all at once, with triethylamine hydrochloride immediately separating out. The reaction solution is heated to boiling for a further 2 hours with stirring, after cooling, the triethylamine hydrochloride is filtered off, which is washed again with 200 ml of toluene, and the piltrate is fractionated on a column. This gives 55 g (92 % of theory) of phenyl isocyanate. 37 g of tetraphenylthiosilane remain as a solid residue.

Example 8

60 g (0.55 M) trimethylchlorosilane are added all at once to a boiling solution of 91.5 (0.5 M) thioncarbanilic acid ether and 56 g (0.55 M) triethylamine in 800 ml of toluene and the mixture is then heated to the boil for 8 hours. The reaction ^{solution is then cooled to 0} ° C., shaken vigorously with 1 liter of ice water in hydrochloric acid to remove the triethylamine hydrochloride, the organic phase is separated off, dried with calcium chloride and distilled, 60 g (88 fi of theory) of phenyl isothiocyanate being obtained.

Example 9

177 g (1 M) of the from allylamine and phenyl chloroformate (or diphenyl carbonate) available N-allyl-O-phenyl urethane are heated to boiling in 1.5 l of dry xylene with 101 g (1 M) of triethylamine and then as quickly as possible 42.5 g (0.25 M) silicon tetrachloride added. It is heated to boiling for another hour, after the hydrochloride has cooled down filtered off, washed with 30 ml of p-xylene and the combined

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ten filtrates distilled through a column, Vfobei 85-87 G 49 g (59 i ° of theory) of allyl isocyanate are obtained.

Example 10

A solution of 48.3 g (0.3 M) cyclohexylcarbamyl chloride in 200 ml carbon tetrachloride is recooled to about -10 ⁰ O and an equally cold solution of 39 -3 g (0 * 3 M) H -Trimethylaily! Acetamide in 250 ml of carbon tetrachloride while stirring and cooling with an ice / table salt Gemiseii quickly
added. Acetamide begins to crystallize out within a few seconds. The mixture is left at 15 ° C. for about 1 hour, then the acetamide (18 g 100 % of theory) is filtered off with the exclusion of moisture and washed with 100 ml of carbon tetrachloride. The trimethylchlorosilane formed and the solvent are distilled off from the combined piltrates at normal pressure over a small column and the remaining cyclohexyl isocyanate is distilled at 10-12 torr over a Claisen attachment. This _{gives 35 t of} 2 g (94 # of theory) of carbamyl chloride-free cyclohexyl isocyanate.

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Claims (1)

Claim Process for the preparation of mono- and polyfunctional derivatives of carbonic acid of the general formula Y =! ) _n where η for integers from 1 to 3, Y for oxygen or Schwefel and R. for one against isocyanates or isothiocyanates is an inert organic radical which can also contain functional groups, functional groups having acidic hydrogen atoms present in silylated form, characterized in that N-silylated carbamic acid derivatives of the general formula R ₁ (NCZR ₂ ) _n "\ R ₃ - Si -R ₅ ^R 4 wherein n, Y and R _{1 have} the above meaning, R ₂ for an isocyanate or isothiocyanate inert, optionally substituted organic radical, Z- for oxygen or sulfur or ZRp for halogen and R ,, R and R, - for a lower one Alkyl, cycloalkyl, aryl, alkoxy, cycloalkoxy, aroxy, acyloxy or siloxanyl radical or halogen or hydrogen, cleaves ^{at temperatures between about -2O 0} C and about 200 ^{0 C.} -16- _BAD ORIGINAL 109883/1871 New prohibitions {to * 4, *. aoz »