This application claims priority filed on 16 September 2022 in Europe with Nr 22196025.5, the whole content of this application being incorporated herein by reference for all purposes.

The current invention concerns a process for the nitrofluorination of olefinic compounds which comprises reacting an olefinic compound with FNO2 and HF.

Certain fluorinated compounds substituted by a nitro-group have been shown to be useful in methods for dielectrically insulating an electrical active parts while having a low GWP (global warming potential), thus being an alternative to the widely applied SFe, which has a high GWP. Such a method is described in WO 2017/191198. Certain a-fluorinated nitroalkanes are also known to be intermediates for the manufacture of herbicides. A method for producing C2F5NO2 is described in EP4001259: C2F5H is lithiated, lithium is then exchanged for Zn, a nitrosogroup is introduced to yield the intermediary product C2F5NO, which is then oxidized to yield C2F5NO2. The multi-step synthesis can be difficult to be implemented on an industrial scale, in particular in view of the organometallic components to be handled. DE3305201 describes the synthesis of a-fluorinated nitroalkanes by nitrofluorination of the corresponding olefins in the presence of a water-binding agent. The method aims to prevent corrosion of steel apparatus which usually occurs when HF/HNO3 is reacted with olefins. Still, the method requires the addition, removal and disposal of the water-binding agent and needs to be controlled such that corrosion is minimized to acceptable level. Improved processes for the manufacture of fluorinated nitro-compounds are thus desirable. Dyatkin et al described in Doklady Akademii Nauk SSSR, 1966, 168(6), pages 1319-22 that nitrofluorination can be achieved starting from alkoxy-substituted olefins with FNO2. It has been found that this reaction does not proceed when applied to olefins that are not alkoxy-substituted.

The present invention thus concerns a process for the nitrofluorination of olefinic compounds, wherein such olefins are not alkoxy-substituted, wherein a compound according to formula (I) is reacted with FNO2 and HF. The present invention provides a new process for the manufacture of certain fluorinated nitroalkanes starting from readily available starting materials. The process can be performed on an industrial scale and gives good or even high yields.

In the present invention, designations in singular are in intended to include the plural; for example, "a solvent" is intended to denote also "more than one solvent" or "a plurality of solvents".

All aspects and embodiments of the present invention are combinable.

In the context of the present invention, the term "comprising" is intended to include the meaning of "consisting of.

The process according to the present invention is a process for a manufacture of a compound or a mixture of compounds according to formula (II), wherein a compound according to formula (I) is reacted with FNO2 and HF wherein

R ¹ is F or Cl

R ² , R ³ and R ⁴ are independently selected from the group consisting of halogen, hydrogen and partially or fully halogenated C1-C4 alkyl.

The term “halogen” intends to denote an element of IUPAC group number 17, in particular F, Cl, Br and I. F and Cl are preferred halogens, and F is the most preferred halogen according to the present invention.

The term “C1-C4 alkyl” denotes methyl, ethyl, n-propyl, i-propyl, n-butyl, isobutyl and tert-butyl. Methyl is the most preferred alkyl group according to the present invention.

The term “partially halogenated C1-C4 alkyl” intends to denote a C1-C4 alkyl group wherein at least one position is substituted by a halogen atom, wherein the term “halogen” is defined as above. The term “fully halogenated Ci- C4 alkyl” denotes a C1-C4 alkyl group wherein all carbon atoms are fully substituted by a halogen atom. For the definition of partially or fully halogenated Ci-C ₄ alkyl groups, F and Cl are the preferred halogens, and F is the most preferred halogen.

R ¹ is defined as F or Cl, wherein F is preferred.

R ² , R ³ and R ⁴ are independently selected from the group consisting of halogen, hydrogen and partially or fully halogenated C1-C4 alkyl. Halogen and fully fluorinated C1-C4 alkyl are preferred for R ² , R ³ and R ⁴ . Most preferably, R ² , R ³ and R ⁴ are independently selected from the group consisting of fluorine, chlorine and CF3. In one preferred aspect, R ¹ is F, two of R ² , R ³ and R ⁴ Cl or F, and one of R ² , R ³ and R ⁴ is partially or fully halogenated C1-C4 alkyl. In another preferred aspect, R ¹ is F, two of R ² , R ³ and R ⁴ are F, and one of R ² , R ³ and R ⁴ is fully fluorinated C1-C4 alkyl, wherein CF3 is preferred.

In one preferred embodiment, R ¹ is defined as F or Cl, and R ² , R ³ and R ⁴ are F or Cl. In a more preferred manner, R ¹ is F, R ² , R ³ and R ⁴ are independently Cl or F. In an even more preferred embodiment, R ¹ , R ² , R ³ are fluorine and R ⁴ is fluorine or chlorine. In a most preferred manner, R ¹ , R ² , R ³ and R ⁴ are F. In this most preferred embodiment, the compound of formula (I) is tetrafluoroethylene.

In another embodiment, the compound of formula (I) is tetrachloroethyl ene .

If the compound of formula (I) is non-symmetrically substituted, a mixture of compounds of formula (II) may form in the process according the present invention.

According to the process of the present invention, the compound of formula (I) is reacted with FNO2 and HF.

FNO2 (nitryl fluoride) is a known compound, and can be prepared according to methods known to the skilled person, such as described in US3110558, US3259460 or A.V. Faloon et al, J. Am. Chem. Soc., 73 (1951), p.- 2937-2938.

In the process of the present invention the compound of formula (I) can be mixed with FNO2 and HF in succession or simultaneously. For example, the compound according to formula (I) is provided, and FNO2 and HF are added consecutively or simultaneously.

In a preferred aspect according to the present invention, a mixture of HF and FNO2 is prepared before reaction with the compound of formula (I). For example, HF is provided in a stirred tank reactor, and FNO2 is introduced into the HF. The reaction can be performed in a gas phase reaction, or gaseous FNO2 can be reacted with liquid HF according to gas-liquid reaction methods known to the skilled person. The reaction is exothermic and preferably is controlled at a temperature of from -20°C to 20 100°C, more preferably at 0 to 50°C, and most preferably at 10 to 20°C by thermocryostat. Depending on the reaction conditions such as temperature, the reaction can be performed at ambient pressure or at a pressure above ambient pressure. When FNO2 is mixed with HF, it is fully electrolytically dissociated (F. Seel et al, Journal of Fluorine Chemistry, 2, 1972/73, page 99 - 101), and depending on the molar ratios, different solvates can form. According to the present invention, the molar ratio of FNO2 and HF is from 1 :3 to 1 :7, preferably, and most preferably, the molar ratio is from 1 :4.5 to 1 : 5.5. FNO2 in HF has also been described (Seel et al) as

FNO2 + / HF -► NO ₂ ⁺ + F(HF ’

FNO2 is used as a gas or as a liquid, wherein its use as gas is preferred, depending on the reaction conditions (boiling point of FNO2 around 200-201° K in A.V. Faloon et al, J. Am. Chem. Soc., 73 (1951), p. -2937-2938) such as temperature and pressure. When FNO2 is used as a gas, it can be used neat or diluted with a suitable inert gas, such as nitrogen, helium and/or argon, wherein its neat use is preferredUse of diluted FNO2 is also possible.

The HF generally is anhydrous , wherein “anhydrous” in intended to denote a content of less that 5000 ppm water as measured by Karl Fischer. Depending on the conditions, it may be used in its gaseous state or in liquid state. The HF can further be used in its neat or diluted form. Neat HF is preferred, and neat HF in liquid form is more preferred. Gaseous HF generally can be diluted with suitable inert gas, such as nitrogen, helium, argon. When a gaseous dilution of HF is used, the HF generally is diluted at a ratio of 1 : 1 to 1 :5. In the reaction of the compound of formula (I) with a mixture of FNO2 and HF, the molar ratio of FNO2 to the compound of formula (I) generally is from 1.0 to 1.5 : 1, preferably rom 1.0 to 1.3 : 1 and most preferably rom 1.0 to 1.2 : 1.

In another aspect of the present invention, an ionic complex or tertiary ammonium complex can be used as source of HF. Such ionic complexes can be, for example, a complex of HF with alkali cations / salts with alkali cations or ammonia NH , such as KF HF, or a tertiary ammonium complex such as Py*HF, NEt3*HF. If an ionic complex or tertiary ammonium complex is used as HF source, the compound of formula (I) is reacted with FNO2 and the ionic HF complex. Generally, the ionic or tertiary ammonium complex and are FNO2 are mixed prior to reaction with the compound of formula (I). The ratio of ionic HF or tertiary ammonium complex and FNO2 usually is 1 :5 For the reaction, the molar ratio ofFNCh to the compound of formula (I) ) generally is from 1.0 to 1.5 : 1, preferably rom 1.0 to 1.3 : 1 and most preferably rom 1.0 to 1.2 : 1. The compound of formula (I) with FNO2 and a ionic HF complex or tertiary ammonium complex generally is performed in an inert solvent, such as acetonitrile or dimethoxyethane. The reaction temperature, pressure range and optional dilution of the compound of formula (I) with a gas are defined as above for the reaction of the compound of formula (I) with HF and FNO2. According to the present invention, the term “HF” includes the ionic complexes and/or tertiary ammonium complexes.

In one preferred aspect of reacting the compound of formula (I) with a mixture of FNO2 and HF, the mixture of FNO2 and HF is furnished in a reactor, and the compound of formula (I) is introduced into the reactor. If the compound of formula (I) is a gas under the reaction conditions, it is provided neat or diluted with a suitable inert gas, such as nitrogen, helium, argon or CO2. If the compound of formula (I) is a fluid under the reaction conditions, it is provided neat or diluted with a suitable inert solvent, such as acetonitrile or dimethoxy ethane. If the compound of formula (I) is a solid under the reaction conditions, it is provided to the reaction in its solid form, or it is provided solved in a suitable inert solvent, such as acetonitrile or dimethoxy ethane.

If the compound of formula (I) is a gas under the reaction conditions, the reaction between the mixture of FNO2 and HF and the compound of formula (I) is performed at a pressure of from Ibar abs. to 6 bar abs., preferably from 1 bar abs. to 5 bar abs., and most preferably from 1 bar abs. to 4.5 bar abs..

The reaction of compound of formula (I) with a mixture of FNO2 and HF generally is performed at a temperature of from -20 to 50°C, preferably at a temperature of from -10 to 40°C, and more preferably at a temperature of from 0 to 30°C.

The compound of formula (II) can be recovered from the reaction mixture according to methods known to the skilled person, such as fractionate distillation, e.g. using cooled traps for the separated reaction mixture components. According to one aspect of the present invention, the process for a manufacture of a compound or a mixture of compounds according to formula (II), wherein a compound according to formula (I) is reacted with FNO2 and HF can be performed batch-wise or in a continuous manner. When the reaction is performed in a continuous manner, it can be performed in, for example, a plug flow reactor.

The invention further concerns a process as described above (except if R ¹ to R ⁴ all are F), wherein in the compound according to formula (I), at least one residue R'-R ⁴ is chlorine, this compound being designated (Ici), wherein (Ici) is reacted with FNO2 and HF, there by giving the compound according to formula (IICIF) and which further comprises a step wherein the compound according to formula (IICIF) is reacted with a fluorination agent, thereby replacing the at least one chlorine residue by a fluorine residue to arrive at a compound according to formula ( 1112) wherein at least two residues R'-R ⁴ are fluorine. The fluorination agent preferably is selected from the group consisting of SbFs/Ch, SbCh/HF, HF, KF/HF, KF, SbFs, Ohla’s reagent, HF -triethylamine complex, tetrabutylammonium fluoride (TBAF), NaF, AIF3/HF, and SbFs/HF, thereby converting at least one chlorine substituent in the compound of formula (II) in one fluorine substituent.

Concerning the , concerning step a), all reaction conditions described above for the general process of reacting a compound according to formula (I) with FNO2 and HF apply.

Concerning the step in which (IICIF) is reacted with a fluorination agent, thereby replacing the at least one chlorine residue by a fluorine residue to arrive at a compound according to formula (II12), suitable reaction conditions are described, for example, in US 4,438,088 and literature cited therein. Gaseous compounds of formula (IICIF) wherein at least one of R ¹ , R ² , R ³ and R ⁴ is Cl generally can be reacted with the fluorination agent in a gas-gas, gas-fluid or gassolid reaction. Suitable solvents for this step generally can be, for example, HF, dichloromethane, dimethylsulfoxide and acetonitrile. The reaction can be performed at ambient pressure or at elevated pressures. The suitable temperature generally can be, depending on reactivity and physical characteristics of the reactants, reagents and product, from -20 to 200°C. The use of catalysts known to catalyse Halex reactions, such as Cr20s, can be advantageous.

The process comprising the steps to convert (Ici) into (IICIF), followed by the reaction wherein (IICIF) is converted into (1112) has the advantage that it can give access to fluorinated compound of formula (II) starting from compounds of formula (I) wherein at least one of R ¹ , R ² , R ³ and R ⁴ is Cl, and wherein the final product compound of formula (1112) is substituted at least two fluorine atoms, thereby expanding the pallet of starting materials (I) for the product of formula (II) which bear more than one fluorine substituent.

The processes according to the present invention offer a new, improved method for the manufacture of the compound of formula (II) from compounds of formula (I) from accessible starting materials, under reaction conditions feasible for industrial scale, in good yields. The obtained products can be used, for example, as refrigerants or for electrical insulation as described in WO 2017/191198.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The following examples are intended to explain the invention further without the intent to limit it.

Example 1 : Manufacture ofFNCh

Starting material NO2 was contained in a gas cylinder with a dip tube, a thermocouple and kept at 20°C with an external armored electric heater. The dip tube was connected to an electronic pressure regulator to keep the internal pressure at 1.6 bar abs with Helium. The gas valve atop the NO2 cylinder was connected to a mass flow controller.

4 NL/h of pure fluorine (20% excess, diluted with 5 NL/h of helium) and 6.68 NL/h of NO2 were fed separately into a stainless steel plug flow reactor tempered by a water jacket at 15°C. The gas phase from the reactor was analyzed via FT-IR: when the bands related to NO2/N2O4 disappeared and those related to FNCh appeared and were stable, the FNO2 product flow was considered ready for use in Example 2.

Example 2: Manufacture of a mixture of HF and FNO2

A stream of FNO2, diluted with helium (6.68 NL/h FNO2 : 5 NL/h helium) as prepared in example 1, were introduced into a 250 ml stirred tank reactor containing 133 g of anhydrous hydrogen fluoride (AHF) and equipped with a head condenser. The reactor vessel was kept at 15°C by a thermocryostat while the head condenser was cooled at -80°C. The composition of the offgas from the condenser was monitored via FT-IR: a sudden and sharp increase in the bands related to FNO2 shows that AHF had been consumed by FNO2; the reactor content was fluxed with pure helium to remove F2 and excess FNO2.

The reaction product, which contained a mixture of FNO2 and HF in an approximate ratio of 1 :5 (measured by gravimetry or mass flow control), and which can also be characterized according to Seel et al (J. Fluorine Chem., 2, 1972/71, page 99-101) as NO2 ⁺ HsF6’, was transferred in a flat-bottom 500 ml stainless steel cylinder equipped with a stirring bar, a pressure gauge and a thermocouple, obtaining 206 g of the adduct. The overall mass recovery was 95%.

Example 3: Manufacture of perfluoronitroethane from tetrafluoroethene

The cylinder with the product of example 2 was connected to a feed line of tetrafluoroethene. The cylinder was cooled to 0°C using a thermocryostat. The Pressure of tetrafluoroethene was gradually increased up to 4.5bar abs., avoiding an increase of the temperature higher than 10°C.

After about 8 hours the internal temperature came back to 0°C, showing that almost all the NO2 ⁺ HsF6’ had been consumed. The cylinder was connected to an ice bath in order to quench the hydrogen fluoride and to recover the organic products in a trap kept in dry ice. After purification, a yield in perfluoronitroethane of 93% was obtained.