JP7364538B2 - Method for preparing halogenated carboxylic acid anhydrides - Google Patents

Description

The present invention claims priority to European Patent Application No. 13170868.7, the entire content of which is incorporated herein by reference for all purposes, in which The present invention relates to a method for preparing a halogenated carboxylic acid anhydride by reacting a halogenated carboxylic acid with sulfuric acid, fuming sulfuric acid and/or disulfuric acid.

Halogenated carboxylic acid anhydrides, such as trifluoroacetic acid, are valuable reagents for the production of various products in the pharmaceutical and agrochemical industries.

It is known to prepare trifluoroacetic anhydride by the reaction of trifluoroacetic acid and phosphoric anhydride. (Hudlicky, Chemistry of Organic Fluorine Compounds, 1976, p. 726). The process described there is disadvantageous for industrial production since the phosphoric anhydride is solid and tends to form amalgams with the reactants and/or products.

The invention therefore now enables an improved process for the production of halogenated carboxylic acid anhydrides. The object of the present invention is to provide a process for the production of halogenated carboxylic acid anhydrides which allows improved yield and/or purity of the product. Furthermore, it is an object of the present invention to provide a process which has a more economical and/or more environmentally friendly waste and/or unwanted by-product profile, e.g. The objective is to provide a method that is more easily separated from substances and/or less toxic and/or less harmful to the environment. Furthermore, it is an object of the present invention to provide a method starting from cheaper and/or more easily available reactants and/or reagents, such as using reactants of lower purity.

These and other objectives are achieved by the method of the present invention.

Accordingly, a first embodiment of the invention provides general structure (I): HalR2C(O)-OC(O)CR2Hal, where Hal is selected from the group consisting of F, Cl and Br; independently selected from the group consisting of H, F, Cl, Br, alkyl and aryl) comprising the general structure (II): HalR2C(O)-OH (of the formula wherein Hal and R are defined as above) is reacted with sulfuric acid, fuming sulfuric acid and/or disulfuric acid.

The term "sulfuric acid" is intended to mean pure sulfuric acid, H2SO4, and aqueous solutions thereof. Preferably, the sulfuric acid used according to the invention has a concentration of 70 wt% or more, more preferably 90 wt% or more, most preferably concentrated sulfuric acid is used, which has a concentration of about 98 wt%.

The term "oleum" is intended to mean a mixture of H2SO4 and SO3. The concentration of fuming sulfuric acid is expressed as either wt% SO3 (referred to as X% oleum) or wt% H2SO4. For example, 65% oleum refers to 114.6 wt% H2SO4. The percentage of SO3 in fuming sulfuric acid is also referred to as free SO3. Therefore, 65% oleum contains 65 wt% free SO3.

The term "dissulfuric acid" is intended to mean H2S2O7.

The term "alkyl" is intended to mean an optionally substituted chain of saturated hydrocarbon-based radicals, such as in particular C1-C6 alkyl. By way of example, mention may be made of methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, isopentyl and hexyl.

The term "aryl" is intended to mean an optionally substituted group derived in particular from an aromatic nucleus such as C6-C10 aromatic nucleus, in particular phenyl or naphthyl.

In a preferred embodiment, Hal is fluorine. More preferably, the compound of general structure (I) is trifluoroacetic anhydride and the compound of general structure (II) is trifluoroacetic acid.

Another embodiment of the invention is to react acetic acid, acetate or a mixture thereof with sulfuric acid, oleum and/or disulfuric acid to form acetic anhydride. Useful examples of acetates include sodium acetate, potassium acetate, calcium acetate, lithium acetate, magnesium acetate, or any mixture thereof. Acetate and/or acetic acid can be used in neat form or as a solution in a solvent, preferably as an aqueous solution.

In another preferred embodiment, the compound of general structure (II) is oleum, preferably from 5 to 95 wt% free SO3, more preferably from 25 to 80 wt% free SO3, most preferably from 50 to 70 wt% of free SO3, particularly with fuming sulfuric acid containing 65 wt% free SO3.

In another preferred embodiment, the halogenated carboxylic acid is present in molar excess relative to the stoichiometry of the reaction. The total amount of halogenated carboxylic acid is preferably from 1.05 to 2 times the stoichiometry, more preferably from 1.05 to 1.10 times the stoichiometry.

Suitably, the reaction is carried out at an elevated temperature, where the internal temperature of the reaction mixture is above the boiling point of the product. Preferably, the reaction is carried out at a temperature in the reaction mixture of 50 to 150°C, preferably 70 to 115°C. The temperature of the reaction mixture refers to the internal temperature in the reaction vessel.

In another preferred embodiment, the product is removed from the reaction mixture by distillation, more preferably distillation is carried out using a packed column. The packed column is suitably packed, for example by Raschig ring. Also preferably, the distillation is carried out using a reflux condenser to control the rate at which product is removed from the reaction mixture.

In another preferred embodiment, the reaction is carried out in a reaction vessel that is at least partially ceramic-lined and/or glass-lined. Suitably, a continuously stirred Powdler vessel with a ceramic lining may be used. Also preferably, the reaction is carried out in a reaction vessel made at least partially of an alloy containing nickel and/or molybdenum. Examples of suitable alloys include Hastelloy B, Hastelloy B-2, or Hastelloy B-3.

A further advantage of the process according to the invention is that highly pure halogenated carboxylic acid anhydrides can be produced in high yields even when lower purity reactants, i.e. halogenated carboxylic acids, are used. It is. For example, a tailing fraction containing unreacted halogenated carboxylic acids and contaminants from a previous reaction can be used in the process of the invention. Thus, recycled halogenated carboxylic acids can be used in the method of the invention. Thus, in preferred embodiments, the halogenated carboxylic acid used in the reaction has a purity of 98% or less, more preferably less than 95% purity, and even more preferably less than 90% purity. Alternatively, the halogenated carboxylic acid used in the reaction has a purity of 50% to 98%, more preferably 50% to 95%, even more preferably 50% to 90%. In another preferred embodiment, the halogenated carboxylic acid used in the method is a product of at least one product from a previous reaction step, at least one reagent, at least one solvent and/or at least one side effect. contained in a mixture that also contains the product.

To the extent that the disclosures of any patents, patent applications, and publications incorporated herein by reference conflict with the description of this application to the extent that they may obscure terminology, the present description shall control.

The invention will now be further illustrated by examples without intending to limit it.

Production of trifluoroacetic anhydride 70.5 kg of trifluoroacetic acid was added to a 115 l ceramic lined Faudler stirred vessel equipped with a 2.5 m packed column packed with 10 mm glass Raschig rings and a condenser, followed by: 19.1 l of 65% oleum, ie with 65 wt% free SO3, was charged. Thereafter, the Faudler vessel was heated to a temperature of 130°C using an oil bath. The product was removed by distillation at a rate of 7.4 kg/h and delivered into a PE-lined metal drum. During the distillation, the temperature of the reaction mixture gradually changed from 78°C to 96°C. The yield of trifluoroacetic anhydride was 64.9 kg (99%). Product purity was >99.9%. In addition, 7.8 kg of tailing fraction was obtained which contained trifluoroacetic anhydride and trifluoroacetic acid, as well as other unspecified by-products. This second fraction can be provided to the reaction mixture of subsequent batches.

Claims (1)

A method for preparing trifluoroacetic anhydride , comprising:
A method comprising reacting trifluoroacetic acid with fuming sulfuric acid .