DD250114A1 - PROCESS FOR THE PREPARATION OF O-ARYLCARBAMATES - Google Patents

Abstract

The invention describes a process for the preparation of O-aryl carbamates from isocyanates and phenols in the presence of acyclic, cyclic and bicyclic amidines and guanidines as catalysts. It is possible with these catalysts, any phenols, in particular sterically hindered phenols, with high space-time yields and low catalyst concentrations to convert to O-aryl carbamates; which are used as herbicides, antioxidants, stabilizers or Isocyanatabspalter technical use.

Description

where the groups mentioned mean: R ¹ = alkyl, isoalkyl, cycloalkyl ", dialkylaminoalkyl, R ² = H, alkyl, alkoxy,

R ³ = methyl, ethyl, isopropyl, cyclohexyl, dialkylaminoalkyl, R ₂ ⁼ - (CH ₂ ^ -, - (CH ₂ ) S-, -CH ₂ CH ₂ OCH ₂ CH ₂ -.

3. The method according to item 1, characterized in that are used as catalysts cyclic aliphatic amidines of the structures Jl and III,

/ - -R ³ - "" ^ - ^ _{TT /} R ³

(0H ₀ ) * · II; (CH _? ) * F III

₂ ) _n

wherein R ¹ , R ² , R ^{3 have} the same meaning as in claim 2 and η = 3-5. 4. The method according to item 1, characterized in that bicyclic amidines of structure IV are used as catalysts,

(CH ₂ ) _n

where η = 3-5 and m = 2-4.

5. The method according to item 1, characterized in that acyclic or cyclic guanidines of structure V are used as catalysts,

₁ sl

R ¹ ~ lf = < ² I γ

\ 4 !

wherein R ¹ , Ri have the same meaning as in claim 2 or by a through a carbon chain - (CH ₂ J _n with η = 2-4 are connected.

6. The method according to item 1-5, characterized in that as phenols, any sterically hindered phenols are used, in particular those which have as o-substituents isopropyl, tert-butyl, bromine, cyano, chlorine and similar groups.

Field of application of the invention

The present invention relates to the preparation of O-aryl carbamates from phenols and mono-, di- and polyfunctional isocyanates using novel catalysts.

-2- 250 114 Characteristic of the known technical solutions

The preparation of O-aryl carbamates from phenols and isocyanates is known and used for a number of technical products. In general, one must work at relatively high temperatures (about 130-170 ° C) to achieve useful sales. However, as high temperatures also cause the retrograde cleavage of O-aryl carbamates, an equilibrium state often sets in. The still freely present isocyanate often tends to enter into side reactions that can lead to considerable proportions of other reaction products. It has therefore been proposed to accelerate the reaction by addition of catalysts, such as. As organotin compounds, metal salts or basic tertiary amines. Although in this case increased reaction rates are achieved, it has been found that the conversions achieved, the product properties, color and odor, in many cases do not meet the desired requirements.

Object of the invention

The aim of the present invention was. To find catalysts that have a high activity for the production of O-aryl carbamates from isocyanates and allow the production of these products in high purity and with useful space-time yields.

Explanation of the essence of the invention

The present invention is the use of acyclic, cyclic and bicyclic amidines as catalysts for the preparation of O-aryl carbamates from phenols and isocyanates. The catalysts of the invention possess exceptional activity for this reaction.

The activity exceeds that of organometallic compounds or the known tertiary amine diazabicyclooctane (DABCO®) many times, which was not expected due to the knowledge of the prior art. With the catalysts according to the invention, both aromatic and aliphatic isocyanates can be converted with phenols to the corresponding O-aryl carbamates. Also sterically hindered phenols, the z. B. tert. Butyl groups in the o-position, react smoothly. Compared with the catalysts of the prior art, the amount of catalyst can be substantially reduced if comparable reaction rates are desired.

The catalysts according to the invention are characterized by the following exemplified compounds:

a) acyclic aliphatic amidines of structure I,

wherein the groups mentioned mean: R ¹ = alkyl, isoalkyl, cycloalkyl, dialkylaminoalkyl R ² = H, alkyl, NRi

R ³ = methyl, ethyl, isopropyl, cyclohexyl, dialkylaminoalkyl r ³ = - (CH ₂ I ₄ -, - (CH ₂ I ₅ -, -CH ₂ CH ₂ OCH ₂ CH ₂ -.

Substituents which bring about a steric hindrance are particularly preferred, b) cyclic aliphatic amidines of the structure II and III,

Ill

wherein R ¹ , R ² , R ^{3 have} the same meaning as in I and η = 3-5

 c) bicyclic aliphatic amidines of structure IV,

(CH ₀ )

where η = 3-5 and m = 2-4. A typical representative of structure IV is diazabicycloundecene, which is known as DBU

 d) acyclic or cyclic guanidines of the structure

Also, a carbon chain - (CH ₂ I _n - may be connected (n = 2-4).) A representative of the structure V, for example, N-phenyl-tetramethylguanidine.With the use of the catalysts of the invention it is possible in a simple manner isocyanates with any phenols To implement the corresponding O-aryl carbamates, which are of importance as herbicides, antioxidants, lubricants and as intermediates for dyes and pharmaceuticals, a special field of application is the preparation of phenol-blocked polyisocyanates, which are used as valuable Isocyanatabspalter for wire and fabric coatings both in suitable solvents and without solvents, the high space-time yields in particular permitting economical operation, the invention being illustrated by the following examples, without limiting the variety of possible applications.

embodiments

Example 1-12: To determine the catalyst activities, 10 ml each of a solution of phenol in ethyl glycol acetate (containing 28.2 g of phenol in 100 ml of solution). 5 ml phenyl isocyanate and an appropriate amount of catalyst mixed in an insulated vessel and the reaction sequence followed by temperature measurement. All solutions and vessels were kept at 50 ° C. Pie catalyst concentration in system was 0.056 moir ¹ . The maximum temperature gradient (ΔΤ / _Μ ) was used as a measure of the activity of the analyzer. The results are shown in Tab.

Table 1

Ispiel Catalyst (AT / At) ™ ,, ¹¹

No.

1 Ν, Ν-Dimethyl-N'-ethylformamidine 2.66

2 N, N-Dimethyl-N'-isopropylformamidine 4.84 Ν, Ν-diisopropyl-N'-cyclohexylformamidine 7.85

4 2-Dimethylamino-1-azacyclo-pentene- (1) 8,61

'j 2-Dimethylamino-1-azacycloheptene (1) 2,48

6 i-butyl-2-methyl-tetrahydropyrimidine 9.89

7 i-ethyl-2-methyl-tetrahydropyrimidine 19,7

8!, Ö-diazabicycloyl-O-undecene-S (DBU) 13.3 -

9 phenyl-tetramethylguanidine (PTMG) '11.9 Comparative Examples:

10 DABCO 1.00

11 N-methylmorpholine 0.13

12 bis-tributyltin oxide 0.15

¹¹ relative to Example 10

Example 13

2.54 g of phenyl isocyanate dissolved in 40 ml of methyl ethyl ketone, with 2.16 g of phenol dissolved in 10 ml of methyl ethyl ketone and brought the stated amounts of catalyst at 5O ⁰ C for reaction. After 5 minutes, the reaction mixture is analyzed by high pressure liquid chromatography. The following amounts of phenol were converted to O-phenyl-N-phenylurethane (Table 2).

Table 2

catalyst 10 ² c / moir ¹ sales Surname 1.32 (in% after 5 min) Dabco 1.26 76 dibutyltindilaurate 2:54 60 triethylamine 0.056 · 89 DBU 0.063 89 PTMG 90

Despite the greatly reduced concentration, the catalysts of the invention provide high conversions.

Example 14-26

0.05 mol of monoisocyanate or 0.025 mol of diisocyanate are mixed with 0.05 mol of a phenol in 50 ml of a suitable solvent and the indicated amounts of 1,5-diazabicyclo [5,4,0] undec-7-ene (DBU) and leave at room temperature. The reactions are often complete in a few minutes. The following O-arylcarbamates are obtained in very pure form (Table 3).

Table 3 example

RNCO

phenol

solvent

DBU /%

Yield /% Fp / ° C

14 PhNCO phenol C ₆ H ₆ 0.005 99 126 15 PhNCO 2,6-di-tert-butyl-4-methylphenol C ₆ H ₆ 0,010 96 134 16 PhNCO 4,4'-thiobis (2-tert-butyl-5- methylphenol) MEK ⁶¹ 0,010 94 244 17 MDI ²¹ Phenol ^: C ₆ H ₆ 0.005 98 188 18 MDI p-cresol CgH ₆ 0.005 99 186-187 19 MDI Ethyl 4-hydroxybenzoate MEK 0,010 98 194-195 20 MDI 2,4,6-tribromophenol MEK 0,020 100 224-225 21 MDJ 2,6-di-tert-butyl-4-methylphenol "CeHe 0,010 96 163-164 22 MDI Ethylene-3-hydroxy-4-tert-butyl benzoate MEK 0,010 93 144-145 23 TDI ³¹ '· 2,6-di-tert-butyl-4-methylphenol C ₆ H ₆ 0.005 88 158-159 24 HDI ⁴⁾ 2,6-di-tert-butyl-4-methylphenol C ₆ H ₆ 0.20 92 210 25 HDI Methyl 4-hydroxybenzoate MEK 0.05 95 116 26 HDI Methyl ^ -hydroxy-S-tert-butyl benzoate C ₆ H ₆ 0.10 91 149-151

¹¹ wt .-% based on isocyanate, ²¹ diphenylmethane-4,4'-diisocyanate, ^3I 2,4- ^tolylene diisocyanate, "'1,6-hexamethylene diisocyanate, ⁵¹ methyl ethyl ketone

Example 27

An NCO-containing reaction product of 87 g 2,4 / 2,6-tolylene diisocyanate (80/20), 13.1 g trimethylolpropane, 6.8 g butanediol (1.3) and 4.4 g p-nonylphenol, dissolved in 111 g of methyl ethyl ketone is added to a solution of 50.9 g of phenol in 51 g of methyl ethyl ketone containing 0.02 g DBU at 60 ° C in about 15 min. An immediate quantitative reaction gives a phenol-blocked polyisocyanate dissolved in methyl ethyl ketone with the following data:

Solids: 49.6% η (22 ⁰ C): 17OmPa s NCObi .: 6.4% NCOfr .: 0.2%

After removal of the solvent leaves a light yellow resin with a softening point of 88-92 ° C, NCO _b i. = 12.6%, NCOfr. = 0.08% and a toluene compatibility of 18.3ml.

Example 28

87g 2,4 / 2,6-tolylene diisocyanate dissolved in 87 g methyl ethyl ketone are cyclotrimerized at 5O ⁰ C with 0.4 g of 2,4-bis-dimethylaminomethyl-cresol. After 2 hours, an NCO content of 13.4% is achieved and the resulting solution is added to a mixture of 53g of phenol, 53g of methyl ethyl ketone and 0.02 g of DBU (in 15 min at 50 ⁰ C). Obtained without Nachreaktionszeit a blocked isocyanurate, dissolved in methyl ethyl ketone with the following data:

Solids: 50% n (22 ° C): 210mPa-s NCObi: 6.8% NCOfr .: 0.13%

After removal of the solvent remains a resin having a softening point of 96-102 ⁰ C, NCObi. = 13.4% NCOfr. = 0.06% and a toluene compatibility of 14.6ml.

Claims (2)

1. A process for the preparation of O-aryl carbamates from isocyanates and phenols, characterized in that are used as catalysts acyclic, cyclic or bicyclic amidines or guanidines. 2. The method according to item 1, characterized in that are used as catalysts acyclic aliphatic amidines of structure I below, HS ³ ₂ ^j