DE1618181B2 - Process for the preparation of carboxylic acid chlorides - Google Patents

Description

It is known to produce carboxylic acid chlorides by reacting phosgene with carboxylic acids (US patent 31 84 506, German patent specification 283 896) or their salts (Chemical Reviews, Vol. 4 [1927], p. 155 and 156; German patents 29 669, 2 84 617). From carboxylic acid anhydrides is off Houben - Weyl, Methods of Organic Chemistry, Vol. 8, p. 469ff., Known that they opposite inorganic acid halides are stable under normal conditions; takes place in special cases a conversion to the acid chlorides only at a higher temperature (phthalic anhydride with phosphorus pentachloride), optionally in the presence of zinc chloride catalysts (succinic anhydride with Thionyl chloride) instead. It is assumed in the aforementioned Chemical Reviews reference that in the conversion to the carboxylic acid chloride, the corresponding anhydride occurs as an intermediate, the German Patents 2 83 896 and 2 84 617 refute this presumption and show that only after Conversion to the carboxylic acid chloride this can form the anhydride in a further stage.

It has now been found that carboxylic acid chlorides are advantageously obtained from the corresponding anhydrides if the carboxylic acid anhydrides are reacted with phosgene at a temperature between 20 and 150 ^° C. in the presence of a catalytic amount of dimethylformamide and / or dimethylaniline.

Compared to the aforementioned method, the method according to the invention provides a simpler one Ways a large number of carboxylic acid chlorides in partially better yield and purity without essential Evolution of hydrogen chloride. With regard to the aforementioned publications, these were results surprising under relatively mild reaction conditions.

Carboxylic acid anhydrides are used as starting materials with one or more, preferably one or two, anhydride groups. Aliphatic, cycloaliphatic, araliphatic or aromatic anhydrides, preferably each with up to 14 carbon atoms, apply; they can still be inert under the reaction conditions Groups or atoms, e.g. B. halogen, may be substituted. The procedure proves itself with unsaturated anhydrides as particularly advantageous because this, for. B. compared to implementation with phosphorus pentachloride, do not polymerize under the process conditions. The carboxylic anhydride can optionally can also be reacted in a mixture with the corresponding carboxylic acid or its carboxylic acid chloride.

So z. B. the following carboxylic acid anhydrides are used as starting materials: acetic acid, Phenylacetic acid, o-toluic acid, a-naphthoic acid, Cyclohexanecarboxylic acid, phthalic acid, dichloromaleic acid, glutaric acid, allyl succinic acid, / 3-crotyl succinic acid, 2-ethylhexanecarboxylic acid, succinic acid, hexahydrobenzoic acid, dichloroacrylic anhydride.

Phosgene is used in stoichiometric amounts or preferably in excess, in particular in up to a 2-fold excess over the stoichiometric amount, used. The reaction takes place at a temperature

ίο between 20 and 150 ⁰ C, preferably between 50 and 120 ⁰ C, carried out without pressure or under pressure, continuously or discontinuously. It is useful to use in the reaction catalysts in the form of carboxamides substituted on the nitrogen atom or lactams or tertiary amines, eg. B. dimethylformamide, N-methylpyrrolidone, dimethylaniline, triethylamine; they are generally added to the reaction in an amount of 0.1 to 20, preferably 0.5 to 2 percent by weight, based on the amount by weight of anhydride. You can in the reaction under the reaction conditions, inert organic solvents, such as aromatic hydrocarbons, z. B. benzene, toluene, xylene; Chlorinated hydrocarbons, e.g. B. chloroform, carbon tetrachloride;

Ether, e.g. B. dioxane, diethyl ether; Petroleum ether; use.

The reaction may be carried out as follows: In the starting material optionally together with catalyst and / or solvent is introduced at the abovementioned temperature for ^l / ₂ to 5 hours phosgene. All systems with a good mixing device, such as stirred kettles and, in particular, circulators or bubble columns, can be used as the reaction vessel. Then from the reaction mixture in the usual way, for. B. separated by fractional distillation, the end product. The carboxylic acid chlorides produced in this way are particularly pure and can be used directly, e.g. B. by hydrogenation according to Rosenmund to the aldehyde, further processed.

The compounds which can be prepared by the process of the invention are valuable starting materials for the production of solvents, pharmaceuticals and dyes.

The parts given in the examples are parts by weight.

example 1

114 parts of glutaric anhydride are heated to 8O ⁰ C and treated with 2 parts of dimethylformamide. At constant temperature, 120 parts of phosgene are introduced into the mixture over the course of 1.5 hours with stirring, and the reaction mixture is then fractionated in vacuo. At 1 Torr, 159 parts of glutaryl chloride pass over in the boiling range from 83 to 85 ° C., corresponding to a yield of 94% of theory.

Example 2

169 parts of glutaryl chloride, 2 parts of dimethylformamide and 114 parts of glutaric anhydride are mixed and heated to 8O ⁰ C. At this temperature, 120 parts of phosgene are passed in with stirring over the course of 1.5 hours, and the mixture is then fractionated in vacuo. At 1 Torr, 321 parts of glutaryl chloride pass over in the boiling range from 83 to 85 ° C. The increase in glutaryl chloride is therefore 152 parts, corresponding to a yield of 90% of theory.

B e i s ρ i e 1 3

A solution of 200 parts of dichloromaleic anhydride and 4 parts of dimethylformamide in 175 parts of benzene is fed at a temperature of 65 to 7O ⁰ C in a bubble column within 3 hours, 240 parts of phosgene. The solvent is then distilled off from the reaction mixture under normal pressure, the residue is fractionated in vacuo and 234 parts of dichloromaleic acid dichloride are obtained in the boiling range from 60 to 65 ° C./2 torr, corresponding to a yield of 88% of theory.

Example 4

In a mixture of 204 parts of acetic anhydride and 5 parts of 220 parts of dimethyl aniline are introduced phosgene at a temperature of 7O ⁰ C with stirring over 3 hours. The distillation of the reaction mixture gives in the boiling range 51 to 52 ° C / 760 torr 257 parts of acetyl chloride, corresponding to a yield of 82% of theory.

Example 5

250 parts of phosgene are introduced into a solution of 50 parts of o-phthalic anhydride and 2 parts of dimethylformamide in 260 parts of xylene with stirring at a temperature of 120 ^° C. over the course of 5 hours. During the reaction, 2 parts of dimethylformamide are slowly added. After cooling to room temperature, the cloudy reaction solution is filtered, then the solvent is distilled off and the residue is fractionated in vacuo. At 1 Torr, 56 parts of o-phthalyl chloride pass over in the boiling range from 100 to 105 ^° C., corresponding to a yield of 83% of theory.
5

Example 6

In a solution of 163 parts of 2-naphthoic anhydride and 5 parts of dimethylformamide in 600 parts Benzene is stirred at a temperature of

ίο 65 ° C within one hour 60 parts of phosgene initiated. The reaction solution is then filtered, the solvent is distilled off and fractionated the residue in vacuo. At 2 torr, 154 parts of 2-naphthoyl chloride go in the boiling range from 120 to 122 ° C about, corresponding to a yield of 79% of theory.

Example 7

50 parts of phosgene are passed into a solution of 105 parts of dichloroacrylic anhydride and 2 parts of dimethylformamide in 150 parts of benzene at a temperature of 60 ° C. in the course of 30 minutes in a circulating apparatus. The reaction solution is filtered off, the solvent is distilled off and the residue is fractionated in vacuo. At 100 torr, 105 parts of dichloroacrylic acid chloride pass over in the boiling range from 83 to 84 ^° C., corresponding to a yield of 82% of theory.

The further examples given in the table are carried out analogously to the aforementioned examples referred to in column 2

example Analogue Output compound Temperature duration Parts catalyst Parts solvent example 8th 4th Crotonic anhydride ( ⁰ Q (hours) 77 Dimethylformamide 2 9 6th o-toluic anhydride 63 Dimethylformamide 2 benzene 10 6th Allyl succinic acid 140 Dimethylformamide 3 benzene anhydride 11th 4th 2-ethylhexanoic acid
anhydride
Succinic acid 135 Dimethylformamide 2 - 12th 6th annyuna
Acetic anhydride 100 Dimethylformamide 2 benzene 13th 4th Dichloromaleic acid 102 Dimethylformamide 2 14th 2 anhydride 100 Dimethylformamide 2 Dichloromormal Phenylacetic acid acid dichloride 15th 6th anhydride 84 Dimethylformamide 2 benzene / J-crotylsuccinic acid- 16 4th anhydride 231 Dimethylformamide 6th - Hexahydrobenzoic 17th 4th acid anhydride 143 Dimethylformamide 3 - (Continuation) Tabel Parts example Parts of phosgene Kp ° C / Torr des yield End product Parts%

9
10
11th
12th
13th
14th
15th
16
17th

200
130

175

100
100

65
60
65
65
75
90
85
65
65
60

0.5

1.5

0.5

120-122 / 760 96 55-59 / 1 61 106-109 / 18 144 73-75 / 12 156 87-89 / 22 130 51-52 / 760 143 60-62 / 2 111 73_74 / 3 79 91-95 / 2 260 73-76 / 20 161

92
79
74
96
84
91
91
77
83
92

Claims (1)

Claim: Process for the preparation of carboxylic acid chlorides from the corresponding anhydrides, characterized in that the carboxylic acid anhydrides are reacted with phosgene at a temperature between 20 and 150 ^° C. in the presence of a catalytic amount of dimethylformamide and / or dimethylaniline.