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1. WO2020002932 - METHOD OF HFO SYNTHESIS

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

METHOD OF HFO SYNTHESIS

The project leading to this application has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 677367).

[0001] This invention relates to a novel method of producing hydrofluoroolefins. In particular, this invention relates to a method of producing dihydrofluorolefins such as HFO-1234ze, HFO-1234yf and HFO-1336-mzz from a fluorinated fluoroolefin, preferably a fully-fluorinated fluoroolefin.

BACKGROUND

[0002] Synthetic refrigerants have improved our quality of life. These are volatile molecules of low molecular mass that typically contain at least one halogen atom. Refrigerants are applied in sealed compressor units in numerous pieces of equipment including fridges, the climate control systems in cars or industrial air-conditioning units. The wide and increasing use of refrigerants is in part responsible for the continued growth of the fluorocarbons industry, which has expanded 10-15 % per annum in recent years.

[0003] Despite their immediate benefit to humanity, synthetic refrigerants and aerosols have been a disaster for the environment. Chlorofluorocarbons (CFCs) contributed to ozone depletion leading to a hole in the ozone layer over Antarctica and were phased out following the agreement of the Montreal protocol in the late 1980s. Their replacements,

hydrofluorocarbons (HFCs) turned out to be equally detrimental to the environment due to their potent global warming potential. For example, 1 tonne of HFC-23 has the same global warming effect as -10,000 tonnes of CO2.

[0004] In 2015, the EU introduced legislation to reduce, contain and replace HFCs. The fluorocarbon industry has responded by beginning the manufacture, marketing and supply of hydrofluoroolefins (HFOs). HFOs have global warming potentials similar to CO2 and do not deplete ozone. These volatile molecules are our most advanced refrigerants and hold promise as a long-term sustainable solution to a long-standing environmental problem.

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[0005] US patents 9255046 B2 and 9233897 B2 describe methods of producing HFOs. In these documents, the mechanism of production proceeds via the selective chlorination and fluorine exchange of propene gas leading to chlorinated intermediates (e.g. HCC-240fa, HCFC-1233zd) and elimination of corrosive hydrogen fluoride gas. These processes occur in the gas phase at moderate temperatures (<220 °C) and pressures (<10 bar), and in the presence of a transition metal containing catalyst often containing toxic metals, such as chromium and thallium, or precious metals, such as iridium and platinum. Use and production of such reagents creates additional environmental hazards and requires specialised equipment and training for safe handling and disposal. There are also cost implications arising from the use of precious metals.

[0006] Thus, there is a need for an improved method for producing HFOs. In particular, there is a need for a simple method that does not involve the use of toxic and/or corrosive starting materials, such as hydrochlorofluorocarbons (HCFCs), or involve toxic or expensive metals to catalyse the reaction. There is also a need for a method that does not result in the generation of toxic intermediates. Further, there is a need for a method for producing HFOs that is economical on a commercial scale.

BRIEF SUMMARY OF THE DISCLOSURE

[0007] In accordance with an aspect of the present invention, there is provided a method of producing a hydrofluoroolefin, wherein said method comprises reacting a fluoroolefin with XZmH3-m*L, wherein X is a group III element, L is a nitrogen, phosphorus, oxygen or sulfur-based ligand, m is from 0 to 2, and Z is a halogen,

and wherein the fluoroolefin is either a fully-fluorinated fluoroolefin, or a fluoroolefin that is fully-fluorinated except from one olefinic hydrogen.

[0008] The method in accordance with the present invention provides a simple method to synthesise hydrofluoroolefins, for example dihydrofluoroolefins such as HFO-1234yf, or a mixture of cis and trans isomers of HFO-1234ze. This method has been found to have a number of advantages over previously known alternative methods. The starting material used in the method of the present invention is a fluoroolefin such as hexafluoropropene, which is an inexpensive and readily available material that may be obtained, for example, in a single step from the fluorination of propene. Other fluoroolefins that may be used as a

starting material can be obtained by fluorination of a corresponding alkene. The synthesis in accordance with the present invention does not involve the use or generation of toxic reagents or intermediates. For example, no HF is generated during the course of reaction. Additionally, no toxic chlorinated intermediates such as hydrochlorofluorocarbons (HCFCs) are generated. Furthermore, because the process in accordance with the present invention is uncatalyzed, no complex mixtures of precious or toxic metals are required in order to perform the reaction.

[0009] Further to the above, the synthesis proceeds via a one-pot reaction, therefore providing a simple method of selectively producing the desired hydrofluoroolefin in high yield. By selecting a particular group III element as X in XZmH3-m*L, a particular

hydrofluoroolefin is obtained. For example, when X is B, a mixture of cis and trans isomers of HFO-1234ze are produced. In another example, when X is Al, HFO-1234yf is produced.

[0010] By-products produced during the synthesis in accordance with the present invention may also be commercially useful, for example BF3 and AIF3. Thus, as well as avoiding the generation of toxic or otherwise undesirable side products such as HCFCs, the method of the present invention involves minimal waste, as the by-products produced may be used in other industrial processes.

[0011] DEFINITIONS

[0012] The term“alkyl” refers to a straight-chain, branched or cyclic alkyl group which may be substituted or unsubstituted. The alkyl group preferably has from 1 to 18 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. The alkyl group may be substituted with at least one substituent selected from the following list: halo, alkyl, alkenyl, alkynyl, aryl, heterocyclyl, thiol, alkylthio, arylthio, alkylthioalkyl, arylthioalkyl, alkylsulfonyl, alkylsulfonylalkyl, arylsulfonylalkyl, alkoxy, aryloxy, aralkoxy, aminocarbonyl, alkylaminocarbonyl,

arylaminocarbonyl, alkoxycarbonyl, aryloxycarbonyl, haloalkyl, amino, trifluoromethyl, cyano, nitro, alkylamino, arylamino, alkylaminoalkyl, arylaminoalkyl, aminoalkylamino, hydroxy, alkoxyalkyl, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, acyl, aralkoxycarbonyl, carboxylic acid, sulfonic acid, sulfonyl, phosphonic acid, aryl, heteroaryl, heterocyclic, or aliphatic. Unless stated otherwise specifically in the specification, an alkyl group is optionally substituted by one or more of the following substituents: halo, cyano, nitro, oxo, thioxo, imino, oximo, tri efhy!si!anyi,— ORa,— SRa,— GC(G)— Ra,— N(Ra)2,— C(0)Ra,—

C(0)ORa,— C(0)N(Ra)2,— N(Ra)C(0)ORa,— OC(O)— N(R3)2,—N(Ra)C(0)Ra,— N(Ra)S(0)tRa (where t is 1 or 2),— S(0)tORa (where t is 1 or 2),— S(0)tRa (where t is 1 or 2) and— S(0)tN(Ra)2 (where t is 1 or 2} where each Ra is independently hydrogen, alkyl, f!uoroaikyi, carbocyc!yl, carbocyclylalkyl, aryl, aralkyl, heterocyclyi, heterocyclylalkyl, heteroaryl or heteroarylalkyl.

[0013] The term“heteroaryl” refers to a 3- to 18-membered aromatic ring system that comprises two to seventeen carbon atoms and from one to six heteroatoms selected from nitrogen, oxygen, sulfur and phosphorus. As used herein, the heteroaryl radical may be a monocyclic, bicydic, tricyclic or tetracyclic ring system, wherein at least one of the rings in the ring system is fully unsaturated, i.e., it contains a cyclic, delocalized (4n+2) rr-e!ectron system in accordance with the HCickel theory. Heteroaryl includes fused or bridged ring systems. Examples of heteroaryis include, but are not limited to, azepinyi, acridinyl, benzimidazoiyl, benzindolyi, 1 ,3-benzodioxolyl, benzofuranyl, benzooxazolyl,

benzo[d]thiazo!yl, benzothiadiazolyl, benzo[b][1 ,4]dioxepinyl, benzo[b][1 ,4]oxazinyl, 1 ,4-benzodioxanyl, benzonaphthofuranyl, benzoxazo!yi, benzodioxo!yl, benzodioxinyl, benzopyranyl, benzopyranonyl, benzofuranyl, benzofuranony!, benzothienyi

(benzothiophenyl), benzothieno[3,2-d]pyrimidinyl, benzotriazoiyi, benzo[4,6]imidazo[1 ,2-a]pyridinyl, carbazolyl, cinnoiinyl, cyclopenta[d]pyrimidinyl, 6,7-dihydro-5H~

cyclopenta[4,5]thieno[2,3-d]pyrimidinyl, 5,8-dihydrobenzo[h]quinazolinyl, 5,6-dihydrobenzo[h]cinnolinyi, 6,7-dihydro-5H-benzo[6,7]cyciohepta[1 ,2-c]pyridazinyl, dibenzofuranyi, dibenzothiophenyl, furanyi, furanonyl, furo[3,2-c]pyridinyl, 5,6,7,8,9,10-hexahydrocycloocta[d]pyrimidinyl, 5,6,7,8,9,10-hexahydrocycloocta[d]pyridazinyi,

5,6,7,8,9,10-hexahydrocycioocta[d]pyridinyl, isothiazoly!, imidazolyl, indazolyl, indo!yl, indazolyi, isoindolyl, indoiinyl, isoindolinyl, isoquinolyl, indoiizinyl, isoxazolyl, 5,8-methano-5,6,7,8-tetrahydroquinazolinyl, naphthyridinyl, 1 ,6-naphthyridinonyi, oxadiazoiyl, 2-oxoazepinyl, oxazoiyl, oxiranyi, 5,6,6a,7,8,9,10,10a~octahydrobenzo[h]quinazoiinyl, 1-phenyi-1 H-pyrroiyl, phenazinyl, phenothiazinyi, phenoxazinyl, phfba!aziny!, pteridinyi, purinyl, pyrroiyl, pyrazolyl, pyrazolo[3,4-d]pyrimidinyi, pyridinyl, pyrido[3,2-d]pyrimidinyl, pyrido[3,4-djpyrimidinyi, pyrazinyl, pyrimidinyi, pyridazinyl, pyrroiyl, quinazolinyi, quinoxaiiny!, quinolinyl, isoquinolinyl, tetrahydroquinolinyl, 5,6,7,8-tetrahydroquinazoiinyl, 5, 6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidinyl, 6,7,8,9-tetrahydro~5H-cyciohepta[4,5]thieno[2,3-d]pyrimidinyi, 5,6,7,8-tetrahydropyrido[4,5-c]pyridazinyi, thiazolyl, thiadiazolyi, triazolyi, tetrazoiyl, triazinyl, thieno[2,3-d]pyrimidinyl, thieno[3,2-d]pyrimidinyi, thieno[2,3-c]pridinyl, and thiophenyl (i.e. thienyl). Unless stated otherwise specifically in the specification, the term“heteroaryl” is meant to include heferoaromafic species as defined

above that are optionally substituted by one or more substituents selected from alkyl, alkenyl, a!kyny!, halo, fluoroaikyl, oxo, thioxo, cyano, nitro, optionally substituted aryl, optionally substituted aralkyl, optionally substituted aralkenyi, optionally substituted ara!kynyl, optionally substituted carbocyciyl, optionally substituted carbocyclylalkyl, optionally substituted heterocyclyl, optionally substituted heterocydy!alkyl, optionally substituted heteroaryl, optionally substituted beteroarylaikyi,— Rb— ORa,— Rb— QC(O)— Ra,— Rb— QC(O)— ORa,— Rb—OC(0)—N(Ra)2,— R„— N(Ra)2,— Rb—C(0)Ra,— Rb— G(0)ORa,— Rb— C(0)N(Ra)2,— Rb—O— Rc—C(0)N(Ra)2,— Rb~- N(Ra)C(G)ORa,— Rb~- N(Ra)C(G)Ra,— Rb— N(Ra)S(0)tRa (where t is 1 or 2),— Rb— S(0)tORa (where t is 1 or 2),— Rb— S(0)tRa (where t is 1 or 2) and— Rb— S(0)tN(Ra)2 (where t is 1 or 2), where each Ra is independently hydrogen, alkyl, fluoroaikyl, cycloalkyl, cycloa!ky!aikyi, aryl, aralkyl, heterocyclyl,

heterocyclylalkyl, heteroaryl or beteroarylaikyi, each Rb is independently a direct bond or a straight or branched a!ky!ene or aikenyiene chain, and Rc is a straight or branched a!ky!ene or aikenyiene chain, and where each of the above substituents is unsubstituted unless otherwise indicated.

[0014] The term“heterocyclic” refers to a non-aromatic ring system having between three to eighteen members, typically having five to twelve members, preferably five to seven, in which one or more ring carbons, preferably one or two, are each replaced by a heteroatom such as N, O, S or P. The heterocyclic species is a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems. The heterocydy! ring or rings are partially or fully saturated. Examples of such heterocyclyl radicals include, but are not limited to, dioxolany!, thienyi[1 ,3]dithianyi, decahydroisoquinolyl, imidazoiiny!, imidazo!idinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl, octahydroindolyl,

octahydroisoindolyl, 2-oxopiperazinyl, 2~oxopiperidinyl, 2-oxopyrrolidinyi, oxazolidinyl, piperidinyl, piperazinyi, 4-piperidonyl, pyrroiidinyl, pyrazolidinyl, quinudidinyl, thiazoiidinyi, tetrahydrofuryl, trithianyl, tetrahydropyranyl, thiomorpholinyl, thiamorpholinyl, 1-oxo-ihiomorpho!inyl, and 1 ,1-dioxo-thiomorpbolinyl. Unless stated otherwise specifically in the specification, the term“heterocyclyl” is meant to include heterocyclyl species as defined above that are optionally substituted by one or more substituents selected from alkyl, alkenyl, a!kyny!, halo, fluoroaikyl, oxo, thioxo, cyano, nitro, optionally substituted aryl, optionally substituted aralkyl, optionally substituted ara!kenyi, optionally substituted ara!kynyl, optionally substituted carbocyciyl, optionally substituted carbocyclylalkyl, optionally substituted heterocyclyl, optionally substituted heterocyc!y!alkyl, optionally substituted heteroaryl, optionally substituted beteroarylaikyi,— Rb— ORa,— Rb— GC(O)— Ra,— Rb— GC(O)— ORa,— Rb— OC(O)— N(Ra)2,— Rb— N(Ra)2,— Ra— C(0)Ra,— R„— C(0)ORa,— Rb—

C(0)N(Ra)2,— Rtr-O— Rc-C(0)N(Ra)2 — Rb— N(Ra)C(0)ORa,— Rb— N(Ra)C(0)R3, -~R -~ N(Ra)S(0)tRa (where t is 1 or 2),— Ru— S(0)tORa (where t is 1 or 2),— -Rb— S(0)tRa (where t is 1 or 2) and— Rb— S(0)tN(Ra)2 (where t is 1 or 2), where each R3 is independently hydrogen, alkyl, fluoroalkyl, cycloalkyl, cycloalkylaikyl, aryl, aralkyl, beterocydy!,

heteroeye!yla!ky!, heteroaryl or heteroarylalkyl, each Rb is independently a direct bond or a straight or branched alkylene or aikenylene chain, and Rc is a straight or branched aikylene or aikenylene chain, and where each of the above substituents is unsubstituted unless otherwise indicated.

[0015] FIGURES

[0016] Figure 1 provides reaction examples for producing organoborane intermediates in accordance with an embodiment of the invention, and structure and 1H NMR data for such exemplary intermediates.

[0017] DESCRIPTION

[0018] In accordance with an aspect of the present invention, there is provided a method of producing a hydrofluoroolefin, wherein said method comprises reacting a fully-fluorinated fluoroolefin with XZmH3-m*L, wherein X is a group III element, L is a nitrogen, phosphorus, oxygen or sulfur-based ligand, m is from 0 to 2, and Z is a halogen, and wherein the fluoroolefin is either a fully-fluorinated fluoroolefin, or a fluoroolefin that is fully-fluorinated except from one olefinic hydrogen.

[0019] The starting material is a fluoroolefin. Preferably, the fluoroolefin is fully fluorinated. Examples of fully-fluorinated olefins include CFsCF=CF2 and CF3CF=CFCF3. Alternatively, the fluoroolefin includes one olefinic hydrogen and may be selected from CF3CH=CF2 or CF3CF=CHF.

[0020] In a preferred embodiment, the starting material is hexafluoropropene (HFP). In another preferred embodiment, the starting material is perfluoro-2-butene.

[0021] The method of the present invention provides a means of synthesising various hydrofluoroolefins. The hydrofluoroolefin produced may be a dihydrofluoroolefin. In one embodiment, the dihydrofluoroolefin is selected from the group consisting of CF3CH=CHF (HFO-1234ze), CF3CF=CH2 (HFO-1234yf), or CF3CH=CHCF3 (HFO-1234mzz).

Alternatively, the hydrofluoroolefin may contain three olefinic hydrogen atoms, for example CF3CH=CH2.

[0022] Example of dihydrofluoroolefins synthesised by the method of the present invention include HFO-1234ze, HFO-1234yf and HFO-1234mzz. One or more of these compounds may be used in a refrigerant composition. Use of compounds synthesised by the method of the present invention in a refrigerant composition is also provided. In particular, HFO-1234ze, HFO-1234yf or HFO-1234mzz, or combinations thereof, may be used in a refrigerant composition.

XZmH3-m»L

[0023] The method of producing a hydrofluoroolefin in accordance with the present invention uses XZmH3-m*L as a reductant. XZmH3-m*L reacts with the fluoroolefin starting material to produce a hydrofluoroolefin.

[0024] X is selected from any suitable group III element. For example, X is selected from the group consisting of Al, B and Ga. In one embodiment, X is Al. In another embodiment, X is B. In one embodiment, where X is selected from B, HFO-1234ze is formed. In an alternative embodiment, where X is selected from Al or Ga, HFO-1234yf is formed.

[0025] Z is a halogen, for example chlorine, fluorine, bromine m is from 0 to 2, for example 1. In one embodiment, m is zero and the reductant contains no halogen. In another embodiment, m is 1 and the reductant is of the formula CZH2·I_, where Z is a halogen.

[0026] L may be any suitable ligand. In particular, L may be a nitrogen, phosphorus, oxygen or sulfur-based ligand. The ligand may contain at least one of nitrogen, phosphorus, oxygen or sulfur. It has been found that the method in accordance with the present invention is sensitive to the nature of the ligand. Without wishing to be bound by theory, it is believed that the effectiveness of the method may be dependent upon the use of weakly-coordinating ligands, for example sulfur-based and nitrogen-based ligands. More specifically, the ligands may be weakly bound and can dissociate to form a reactive intermediate, such as BH3 or AIH3. This allows the addition of the reactive intermediate to the fluoroolefin starting material to form an organoborane intermediate. Alternatively, for example where X is Al, the ligand may remain bound to Al during transformation of the fluoroolefin without the above-mentioned dissociation.

[0027] In one embodiment, the ligand is sulfur-based, for example SR1R2. In another embodiment, the ligand is nitrogen-based, for example NR1R2R3.

[0028] Each of R1, R2 and R3 may independently be a C1-C18 alkyl group. The alkyl group may be linear or branched. In a preferred embodiment, the alkyl group is linear.

[0029] In one embodiment, each of R1, R2 and R3 is independently an alkyl group of 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, for example 1 to 6 carbon atoms. In one embodiment, each of R1, R2 and R3 is independently a methyl group, ethyl, propyl or butyl group. In a preferred example, each of R1, R2 and R3 are methyl. The alkyl group may be a linear or branched alkyl group, and may be substituted or unsubstituted. Each of R1, R2 and R3 may be identical. Alternatively, the ligand may include at least two different alkyl groups, for example three different alkyl groups.

[0030] In another embodiment, the ligand may contain more than one S or N atom. The ligand may take the form of a linked S or N donor, in which the sulfur or nitrogen atoms are linked by alkyl groups. The alkyl groups may be substituted or unsubstituted and may be branched or linear, and may contain from 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, for example 1 to 6 carbon atoms. In one embodiment, the ligand may contain between two and ten sulfur or nitrogen atoms, preferably between two and five sulfur or nitrogen atoms, for example two or three sulfur or nitrogen atoms.

[0031] In one embodiment, where the ligand is SR1R2, at least one of R1 and R2 may be independently selected from R4SR5 wherein R4 is a Ci to C12 alkyl group and R5 is hydrogen or a C1 to C12 alkyl group. In one embodiment, both of R1 and R2 are independently selected from R4SR5. In an alternative embodiment, R1 is selected from R4SR5 and R2 is selected from hydrogen or a C1-C18 alkyl group as defined above.

[0032] In a preferred embodiment, the bridged ligand is CH3-S-CH2CH2-S-CH2CH2-S-CH3.

[0033] Where the ligand is NR1 R2R3, at least one of R1 , R2 and R3 may be independently selected from R4NR5R6 wherein R4 is a C1 to C12 alkyl group, and each of R5 and R6 are independently hydrogen or a C1 to C12 alkyl group. In one embodiment, each of R1 , R2 and R3 are independently selected from R4NR5R6. In another embodiment, R1 is selected from R4NR5R6, and R2 and R3 are independently selected from hydrogen or a C1 to C12 alkyl group. In a further embodiment, R1 and R2 are selected from R4NR5R6, and R3 is hydrogen or a C1 to C12 alkyl group.

[0034] In a further embodiment, the ligand may comprise a polymeric material, wherein the polymeric material comprises either N or S, or may comprise both N and S. In one embodiment, the material may comprise repeat units containing between 1 to 10 sulfur or nitrogen atoms for a small chain oligomer. In a further embodiment, the material may comprise repeat units containing 1 to 10,000 sulfur or nitrogen atoms. The polymeric material may take the form of a solid mesh or grating. The polymeric material may be linear or branched.

[0035] In another embodiment, L may be a cyclic nitrogen, phosphorus, oxygen or sulfur-based ligand. The heterocyclic structure may be aromatic or non-aromatic. The cyclic structure may include fused or bridged ring systems, and may be monocyclic, bicyclic, tricyclic or tetracyclic. Preferably, the cyclic structure is monocyclic.

[0036] Examples of heterocyclic ligands include dioxolane, thienyi[1 ,3]dithiane,

decahydroisoquinoline, decahydroquinoline, imidazoline, imidazolidine, isothiazolidine, isoxazolidine, morpholine, octahydroindoie, octahydroisoindole, 2-oxopiperazine, 2-oxopiperidine, 2-oxopyrrolidine, 1 ,3-dioxolane, 1 ,3-oxathioiane, 1 ,2-oxathioiane, 1 ,4-dioxane, oxazolidine, oxepane, piperidine, piperazine, 4~piperidone, pyrrolidine, pyrazo!idine, pyrrolizidine, quinuclidine, tetrahydrothiophene, thiazolidine, thiane, 1 ,3-dithiane, 1 ,4-dithiane, 1 ,3,5-trithiane, tetrahydrofuran, trithiane, tetrahydrothiophene, tetrahydropyran, thiomorphoiine, thiamorpholine 1-oxo-thiomorpholine, 1 , 1-dioxo-thiomorpholine. The heterocyclic ligand may be substituted or unsubstituted.

[0037] In a preferred embodiment, L is a cyclic nitrogen-based or sulfur-based ligand. In one example, L is tetrahydrothiophene.

[0038] THFBHs (CAS# 14044-65-6), Me2S BH3 (CAS# 13292-87-0), BCh (CAS# 10294-34-5) and BBr3 (CAS# 10294-33-4) are commercially available (e.g. Sigma-Aldrich, Alfa Aesar, Fischer Scientific) and are generated on a large scale industrially. Formation of the mixed BZmHs-m-L species can be carried out by mixing the appropriate ratio of BH3 and BZ3 [(3-m):(m), wherein m is from 0 to 2] complex in hydrocarbon or halohydrocarbon solvent with an equivalent of the desired ligand L (H. C. Brown, J. Org. Chem. 1986, 51(26), 5264-70), or by reaction of L.BH3 with Ph3CZ in the ratio (3-m):(m) in hydrocarbon solvent (S. A. W. Jones, Aust. J. Chem. 1987, 40, 987). Alternatively, BZmH3-m L can be generated by the addition of R3SiH (R = alkyl) with BZ3 in the ratio (3-m):(m/3) in the presence of ligand L (H. C. Brown, Angew. Chem. Int. Ed. 1999, 38, 2052).

[0039] L AIH3 can be generated from slow addition of the protonated ligand [L.H+][X] with commercially available LiAlhU (CAS# 16853-85-3) in hydrocarbon solvent (N. D. Miro, Inorganic Syntheses 1977, 17, 36-42).

Method

[0040] The method of producing a hydrofluoroolefin in accordance with the present invention proceeds via the selective substitution of fluorine for hydrogen in the starting material, wherein the starting material is a fluoroolefin such as hexafluoropropene. This substitution is known as hydrodefluorination. More specifically, in the method of producing a hydrofluoroolefin in accordance with the present invention, two olefinic fluorine atoms are replaced by hydrogen atoms. In one embodiment, the starting material is fully-fluorinated, and the hydrofluoroolefin produced is a dihydrofluoroolefin such as CF3CH=CHF,

CF3CF=CH2, or CF3CH=CHCF3. In an alternative embodiment, the starting material has one olefinic hydrogen.

[0041] Without wishing to be bound by theory, it is believed that the method of producing a hydrofluroolefin in accordance with the present invention proceeds via a series of addition-elimination processes. First, it is believed that XZmH3-m*L coordinates to the fluoroolefin starting material to form an organoborane intermediate. This addition step is termed

hydroboration. This step is understood to be followed by the breaking of a carbon-fluorine bond by b-fluoride elimination, and generation of pentafluoropropene intermediates (in the case where the starting material is HFP). Said intermediates may be short-lived and may not be observed directly. The pentafluoropropene intermediate may undergo a further addition-elimination sequence, thus providing the hydrofluoroolefin end product.

Alternatively, either or both of said addition-elimination sequences could proceed by a direct H/F exchange. In this concerted process, breakage of a C-F bond and formation of a B-F bond occurs in a simultaneous manner.

[0042] In an alternative embodiment, the starting material has one olefinic hydrogen. In this embodiment, a dihydrofluoroolefin may also be produced. In this embodiment, the dihydrofluoroolefin is produced by one addition-elimination process, instead of the two addition-eliminations involved when the starting material is a fluoroolefin such as

hexafluoropropene.

[0043] The method in accordance with the present invention may be carried out under conditions effective to provide a conversion of at least about 60%, preferably at least about 75%, more preferably at least about 80%, for example at least about 85%. The conversion refers to the percentage amount of fluoroolefin starting material that has been converted to the desired hydrofluoroolefin. Where a mixture of cis and trans isomers is produced, for example cis and trans of HFO-1234ze, the percentage conversion refers to the total percentage of both the cis and trans isomers produced. Other minor products of the synthesis may result from over-reduction or under-reduction of the fluoroolefin starting material. In the case of under-reduction, only one F atom is replaced with hydrogen. In the case of over-reduction, three F atoms are replaced with hydrogen. Conversion of the fluoroolefin starting material to minor products at the completion of the hydrofluoroolefin synthesis in an amount of less than 30%, preferably less than 20%, more preferably less than about 15%. In one example, the minor products resulting from over-reduction or under reduction may be present in an amount of less than 10%.

[0044] The method may be carried out at a temperature of between 10 - 150°C, preferably between 20 - 120°C, for example between 25 - 100°C. The method in accordance with the present invention can involve reaction in the liquid phase or, in certain embodiments, it may comprise a gas phase or combination of gas and liquid phase reactions. The reaction may

be carried out at any suitable pressure. The pressure may be between 1 to 10 bar, preferably 1 to 5 bar, for example 1 to 2 bar.

[0045] The reaction may be carried out until the desired conversion to hydrofluoroolefin is achieved. In some embodiments, the reaction may be carried out over a period of at least 10 hours, preferably at least 24 hours, more preferably at least 48 hours. In one example, the reaction is carried out over a period of up to 96 hours. While the synthesis can be continued beyond 96 hours, no significant increase in conversion is observed. Where the starting material is a fluoroolefin containing one olefinic hydrogen such as CF3CH=CF2 or CF3CF=CHF, the reaction time may be shorter than the reaction time for a fully fluorinated fluoroolefin. Progress of the reaction can be monitored using at least one of 1H NMR and 19F NMR spectroscopy.

[0046] Where X is Al, a by-product of the hydrofluoroolefin synthesis is aluminium trifluoride (AIF3). This is a solid that is produced as a by-product from each of the addition-elimination reactions. AIF3 is of useful industrial value. For example, AIF3 is useful in conjunction with cryolite for the electrochemical extraction of aluminium metal from bauxite ore. An additional use of AIF3 is as part of an isomerisation catalyst for the conversion of cis- HFO-1234ze to frans-HFO-1234ze, which may be carried out during, for example, the method of industrial manufacture of HFO-1234ze described in US 9255046 B2.

[0047] Where X is B, a by-product of the hydrofluoroolefin synthesis is BF3*L. This is produced as a by-product from each of the addition-elimination reactions and is also of useful industrial value, given that it is a Lewis acid.

[0048] In another embodiment, there is provided a method of producing organoborane compounds such as L*BH2{CF(CF3)CF2H)} or L*BH2{CF(CF3)CF(CF3)H)} that may be useful as intermediates in the production of hydrofluoroolefins, for example. These compounds may also have use as chemical“building blocks” in various synthesis reactions. Such intermediate compounds may be obtained from partially or fully-fluorinated

fluoroolefins. For example, said method may comprise the steps of providing a fluorinated reagent selected from CF3FC=CF2 or CF3CF=CFCF3; and reacting the fluorinated reagent with XZmH3-m*L, wherein X is boron, L is a weakly-coordinating ligand as detailed above, m is from 0 to 2, and Z is a halogen; at a temperature of between 20 - 150 °C for a time period of between 5 min and 20 hours. In another embodiment, a method of producing

L*BH2{CF(CF3)(CFH2)} or L*BH2{CH2CHF(CF3)} is provided. Said method may comprise the steps of providing a partially fluorinated reagent selected from FHC=CFCF3 or

H2C=CFCF3, for example, and reacting the partially fluorinated reagent with XZmH3-m*L, wherein X is boron, L is a weakly-coordinating ligand as detailed above, m is from 0 to 2, and Z is a halogen; at a temperature of between 20 - 150 °C for a time period of between 5 min and 20 hours. Exemplary methods for producing organoborane compounds in accordance with the invention are provided in Figure 1.

Production of HFO-1234ze

[0049] In a preferred embodiment, hexafluoropropene undergoes selective

hydrodefluorination to HFO-1234ze on reaction with BH3*SR2, where R is a C1-C18 alkyl group, preferably C1-C12 alkyl group, for example a C1-C6 alkyl group. The synthesis proceeds at moderate pressure and temperature. The synthesis may be performed at pressures of 1 to 5 bar, preferably 1 to 2 bar, for example about 1 bar. In terms of reaction temperature, the synthesis may be performed at temperatures of from 10 to 150 °C, preferably 80 to 120 °C, for example 90 to 110 °C.

Me Me

\ \


2 3 2 3

HFP HFO-1234ze

[0050] In the synthesis of HFO-1234ze as shown above, BH3 initially adds to HFP to form an organoborane intermediate. This initial step may be performed at temperatures of between 10 to 150 °C, preferably 80 to 120 °C, for example 90 to 110 °C. The step may be completed within a period of up to 120 minutes, for example up to 90 minutes, for example up to 60 minutes.

[0051] Following the production of the organoborane intermediate, b-fluoride elimination generates a pentafluoropropene intermediate. This b-fluoride elimination step may be performed at temperatures of between 20 to 150 °C, preferably 80 to 120 °C, for example 90 to 110 °C. The b-fluoride elimination step may be completed within a period of between 10 and 80 hours, preferably between 15 and 70 hours, for example between 24 and 48 hours.

[0052] The pentafluoropropene intermediate then undergoes a further addition-elimination sequence to form HFO-1234ze. This step may be performed at temperatures of between 10 to 150 °C, preferably 80 to 120 °C, for example 90 to 110 °C, and may be completed within a period of between 5 and 50 hours, preferably between 10 and 40 hours, for example between 15 and 30 hours.

[0053] Under these conditions, the transformation may be completed within 120 hours, preferably within 100 hours, for example within 90 hours. Within this time period, up to 70%, preferably up to 75%, more preferably up to 80%, for example 85% of the hexafluoropropene has been converted to HFO-1234ze. Following the reaction of HFP with BH3*SR2, only a minimal amount of HFO-1234yf is observed as a reaction product. Preferably, no HFO-1234yf is obtained. Completion of the reaction may be quantitatively observed by 1H and 19F NMR spectroscopy with measurements showing the formation of HFO-1234ze, and the consumption of hexafluoropropene within the reaction mixture.

[0054] Other products of the reaction of HFP with BH3*SR2 include trifluoropropene. This may be produced in a small amount due to over-reduction of HFP. Less than 10% of trifluoropropene may be observed, preferably less than 5%, for example less than 2%. Also observed in the reaction of HFP with BH3*SR2are pentafluoropropenes. These may be produced in small amounts due to under-reaction of HFP. Less than 20% of

pentafluoropropenes may be observed, preferably less than 15%, for example less than 12%.

[0055] In the synthesis of HFO-1234ze as shown in the scheme above, a mixture of cis-trans isomers of HFO-1234ze is produced. In one embodiment, the trans isomer is in excess at the end of the synthesis. The ratio of trans to cis may be 5: 1 to 1 :1 , preferably 4: 1 to 1 :1 , for example 3:1 to 1 :1. In terms of the percentage conversion to the trans isomer, a conversion of between 40 and 70%, preferably between 50 and 60% may be achieved. For the percentage conversion to the cis isomer, a conversion of between 20 and 40%, preferably between 25 and 35% may be achieved.

[0056] Following the synthesis of the mixture of cis and trans isomers of HFO-1234ze, the cis and trans isomers may be separated by any suitable method. For example, cis and trans isomers may be separated as described in US 9255946 B2. Conversion of the cis-isomer to

the trans-isomer may also be desired. This conversion may be performed by heating the cis-isomer over an appropriate catalyst, for example AIF3.

[0057] In another embodiment, perfluoro-2-butene undergoes selective hydrodefluorination to HFO-1336mzz on reaction with BH3*SR2. The synthesis may proceed as described above for HFO-1234ze.

Production of HFO-1234yf

[0058] In another preferred embodiment, hexafluoropropene undergoes selective hydrodefluorination to HFO-1234yf on reaction with AIH3*NR3, where R is as described above. Preferably, R is a C1-C18 alkyl group, more preferably a C1-C12 alkyl group, for example a C1-C6 alkyl group. The synthesis proceeds at moderate pressure and

temperature. The synthesis may be performed at pressures of 1 to 5 bar, preferably 1 to 2 bar, for example about 1 bar. In terms of reaction temperature, the synthesis may be performed at temperatures of from 10 to 100 °C, preferably 10 to 70 °C, for example 10 to 50 °C.

[0059] An exemplary reaction scheme for hydrodefluorination of hexafluoropropene to HFO-1234yf is provided below.


Exemplary reaction scheme for hydrodefluorination of hexafluoropropene to HFO-1234yf

[0060] In the synthesis of HFO-1234yf from hexafluoropropene, the initial addition-elimination reaction produces a pentafluoropropene intermediate. The initial addition-elimination step may be performed at temperatures of between 10 and 30 °C, preferably between 15 and 25 °C, for example at about 20 °C. The initial addition-elimination reaction may be completed within a period of up to 1 hour, for example up to 30 minutes, for example up to 10 minutes. In one example, the initial addition-elimination reaction may be completed within a period of up to 5 minutes. The second step of the synthesis in which HFO-1234yf is produced, may be performed at temperatures of between 10 and 60 °C, for example between 20 and 50 °C, for example between 35 and 45 °C. The second step may be completed within a period of between 10 and 48 hours, preferably between 15 and 36 hours, for example between 18 and 24 hours.

[0061] Alternatively, the synthesis of HFO-1234yf may be performed at a constant temperature throughout, and may occur instantaneously at room temperature (e.g. 20 to 25 °C). For example, the entire synthesis of HFO-1234yf may be performed at temperatures of between 10 to 50 °C, such as 15 to 25 °C. Where the synthesis is performed at a constant temperature throughout, the synthesis may be completed within a period of between 10 and 48 hours, preferably between 15 and 36 hours, for example between 18 and 24 hours.

[0062] Under the above conditions, the transformation may be completed within 120 hours, preferably within 100 hours, for example within 90 hours. Within this time period, up to 80%, preferably up to 90%, more preferably up to 95%, for example 98% of the hexafluoropropene has been converted to HFO-1234yf. Following the reaction of HFP with AIH3*NR3, only a minimal amount of HFO-1234ze is observed as a reaction product. Preferably, no HFO-1234ze is obtained. Completion of the reaction may be quantitatively observed by 1H and 19F spectra showing the formation of HFO-1234yf, and the consumption of

hexafluoropropene within the reaction mixture.

[0063] A by-product of each of the addition-elimination reactions is AIF3. This is

precipitated as a white solid. Observation of the amount of AIF3 precipitate formed provides a method of qualitatively monitoring the course of the reaction.

[0064] Other products of the reaction of HFP with AIH3*NR3 include trifluoropropene. This may be produced in a small amount due to over-reduction of HFP. Less than 10% of trifluoropropene may be observed, preferably less than 5%, for example less than 2%. Also observed in the reaction of HFP with AIH3*NR3 are pentafluoropropenes. These may be produced in small amounts due to under-reaction of HFP. Less than 20% of

pentafluoropropenes may be observed, preferably less than 15%, for example less than 12%.

[0065] In a further embodiment, hexafluoropropene may undergo selective hydrodefluorination to HFO-1234yf on reaction with GaH3*NR3, wherein R is as described above. Preferably, R is a C1-C18 alkyl group. Formation of HFO-1234yf from

hexafluoropropene on reaction with GaH3*NR3 may proceed as described above for AIH3*NR3. A by-product of each of the addition-elimination reactions is GaF3, which is precipitated as a white solid.

EXAMPLES

[0066] Synthesis of HFO-1234ze using (Me2S)BH3

Me2S BH3 (38 mI, 0.4 mmol) dissolved in Obϋd (0.6 ml) was degassed by the freeze-pump-thaw method. Hexafluoropropene (1 atm, 2 ml, 0.08 mmol) was allowed to fill the J-Young’s NMR tube and the reaction mixture was heated to 100 °C for 96 h. The volatiles were distilled under reduced pressure and condensed at -196 °C to give HFO-1234ze in 81 % yield based on initial HFP concentration (£:Z ratio of 2.1 : 1). Minor products include 1-hydropentafluoropropene (13%, E\Z ratio 1 :3.6), trifluoropropene (<2%) and 3,3,3-trifluoropropyl-borondifluoride (5%).

E-HFO-1234ze

1 H NMR (C6D6, 400 MHz, 298 K): dH 6.29 (1 H, ddq, 2 HF = 77.2, 3 HH = 1 1.1 , 4 HF = 2.3 Hz, HCF), 4.93 (1 H, m, HCCF3).

19F{1 H} NMR (C6D6, 376 MHz, 298 K): dR -61.48 (d, 3 FF = 8.8 Hz, CF3), -1 19.07 (q, 3 FF = 8.5 Hz, CF).

Z-HFO-1234ze

1 H NMR (C6D6, 400 MHz, 298 K): dH 5.53 (1 H, dd, 2 HF = 77.0, 3 HH = 5.5 Hz, HCF), 4.34 (1 H, dm, 3 HF = 36.6 Hz, HCCF3).

19F{1 H} NMR (C6D6, 376 MHz, 298 K): dR -58.37 (d, 3 FF = 17.0 Hz, CF3), -110.37 (q, 3 FF = 16.4 Hz, CF).

[Me2S BH3] E-HFO- Z-HFO- 1-H- trifluoropropene

(inM) 1234ze 1234ze pentafluoropropene


667 54% 27% 13% 2%

Table 1: Effect of initial concentration of [Me2S BH3] on yield of fluorinated gaseous products after 96 h at 100 °C. ^ 48 h.

[0067] Synthesis of HFO-1234yf using (Me3N)AIH3

[0068] MbbN AIHb (18 mg, 0.2 mmol) dissolved in Obϋd (0.6 ml) was degassed by the freeze-pump-thaw method. Hexafluoropropene (1 atm, 2 ml, 0.08 mmol) was allowed to fill the J-Young’s NMR tube and the reaction mixture was heated to 40 °C for 90 h. The volatiles were distilled under reduced pressure and condensed at -196 °C to give HFO-1234yf in 98% yield. Minor product of trifluoropropene observed in 2% yield.

HFO-1234yf

1H NMR (C6D6, 400 MHz, 298 K): dH 4.44 (1 H, dd, 3 HF = 43.9, 2 H H = 4.7 Hz, CH2), 4.31 (1 H, dm, 3 HF = 14.7 Hz, CH2).

[0069] 19F{1H} NMR (C6D6, 376 MHz, 298 K): dR -73.35 (d, 2 FF = 11.1 Hz, CF3), -124.34 (q, 2 FF = 10.9 Hz, CF).

[0070] Synthesis of (Ph3P)BH2{CF(CF3)(CF2H)}


[0071] Me2S BH3 (48 mI, 0.5 mmol) dissolved in toluene (5 ml) was degassed by the freeze-pump-thaw method. Hexafluoropropene (1 atm, 15 ml, 0.6 mmol) was allowed to fill in the flask and the reaction mixture was heated to 100 °C for 1 h. PPh3 (131 mg, 0.5 mmol) was added and the reaction was heated to 40 °C for 16 h to 18 h. Removal of the volatiles under reduced pressure and trituration with pentane yielded the title complex as a colourless solid in 63% yield. Dissolution in Et20 and storage at -30 °C gave colourless crystals suitable for X-ray diffraction analysis.

1 H NMR (C6D6, 400 MHz, 298 K): dH 7.55 (6H, m, CH-Ph), 6.93 (9H, m, CH-Ph), 5.86 (1 H, t d, 2 HF = 55.0 Hz, 3 HF = 8.7 Hz, CF2H), 2.71 (2H, br, BH2).

13C NMR (C6D6, 100 MHz, 298 K): d0 134.2 (d, 1 CP = 19.8 Hz, C-Ph), 133.9 (d, 3 CP = 9.1 Hz, CH-Ph), 131.6 (CH-Ph), 128.9 (d, 2 CP = 10.6 Hz, CH-Ph), 126.1 (m, CF3), 114.6 (t d, 1 CF = 246.2 Hz, 2 CF = 29.1 Hz, CF2H), 96.4 (br, CF).

11 B NMR (C6D6, 128 MHz, 298 K): dB -28.3 (br d, 1 BP = 78.6 Hz, BH2).

19F NMR (C6D6, 376 MHz, 298 K): dR -74.43 (d, 3 FF = 7.3 Hz, CF3), -127.16 (dd, 2 FF = 295.3 Hz, 2 FH = 55.3 Hz, CF2H), -128.17 (dd, 2 FF = 295.3 Hz, 2 FH = 56.5 Hz, CF2H), -191.87 (m, CF).

31 P NMR (C6D6, 162 MHz, 298 K): dR 14.68 (br d, 1 BP = 76.6 Hz).

[0072] Synthesis of (Ph3P)BH2{CF(CF3)(CFH2)}


LiAIH4 or Me3N AIH3 (0.1 mmol) was dissolved in Et20 (0.1 ml) and Obϋd (0.5 ml) in a J-Young’s NMR tube and was degassed by the freeze-pump-thaw method.

Hexafluoropropene (1 atm, 2 ml, 0.08 mmol) was allowed to fill the tube and the reaction mixture was shaken to ensure mixing. After 5 min, white precipitate was clearly visible and the contents of the tube were condensed via vacuum transfer onto THF BH3 (40 pi, 1 M THF, 0.04 mmol).

[0073] The reaction mixture was sonicated for 1 h, then PPh3 (10.5 mg, 0.04 mmol) was added and the reaction continued for 24 h. Removal of the volatiles under reduced pressure and trituration with pentane yielded the title complex as a colourless solid. Dissolution in Obϋd allowed for analysis by NMR spectroscopy.

[0074] 1 H NMR (C6D6, 400 MHz, 298 K): dH 7.55 (6H, m, CH-Ph), 6.93 (9H, m, CH-Ph), 4.74 (1 H, dddd, 2 HF = 61.8 HZ, 3 HF = 39.9 Hz, 2 H H = 11.8 Hz, 4 HF = 1.8 Hz, CFH2), 4.49 (1 H, dddd, 2 HF = 62.1 Hz, 3 HF = 15.1 Hz, 2 H H = 1 1.8 Hz, 4 HF = 1.8 Hz, CFH2), 2.48 (2H, br, BH2).

11 B NMR (C6D6, 128 MHz, 298 K): dB -27.8 (br d, 1 BP = 73.8 Hz, BH2).

19F NMR (C6D6, 376 MHz, 298 K): dR -74.54 (d, 3 FF = 10.4 Hz, CF3), -186.86 (br, CF), -220.55 (t, 2 FH = 50.3 Hz, CFH2).

31 P NMR (C6D6, 162 MHz, 298 K): dR 14.78 (br).

[0075] Synthesis of (Ph3P)BH2{CH2CHF(CF3)}


[0076] THF BH3 (40 mI, 1 M THF, 0.04 mmol) dissolved in Obϋd (0.5 ml) was degassed by the freeze-pump-thaw method. 2,3,3,3-tetrafluoropropene (1 atm, 2 ml, 0.08 mmol) was allowed to fill in the flask and the reaction mixture was sonicated for 1 h. PPh3 (10.5 mg,

0.04 mmol) was added and the reaction was sonicated for 2 h. Removal of the volatiles under reduced pressure the title complex as a colourless solid. Dissolution in Obϋb allowed for analysis by NMR spectroscopy, including the relative selectivities of Markovnikov vs. anti-Markovnikov addition.

Markovnikov (45% by 1 H NMR spectroscopy)

1 H NMR (C6D6, 400 MHz, 298 K): dH 7.59 (6H, m, CH-Ph), 6.98 (9H, m, CH-Ph), 2.49 (2H, br, BH2), 1.58 (3H, d, 3 H F = 23.8 Hz, CH3).

11 B NMR (C6D6, 128 MHz, 298 K): dB -25.5 (br d, 1 BP = 72.5 Hz, BH2).

19F NMR (C6D6, 376 MHz, 298 K): dR -79.47 (m, CF3), -168.41 (br, CF).

31 P NMR (C6D6, 162 MHz, 298 K): dR 14.30 (br).

Anti-Markovnikov (55% by 1 H NMR spectroscopy)

1 H NMR (C6D6, 400 MHz, 298 K): dH 7.47 (6H, m, CH-Ph), 6.96 (9H, m, CH-Ph), 4.93 (1 H, dqdd, 2 HF = 58.8 Hz, 3 HF = 9.1 Hz, 3 HH = 6.4 Hz, 3 HH = 5.5 Hz, CHF), 2.51 (2H, br, BH2), 1.38 (2H, m, CH2).

11 B NMR (C6D6, 128 MHz, 298 K): dB -28.7 (br, BH2).

19F NMR (C6D6, 376 MHz, 298 K): dR -79.49 (m, CF3), -187.65 (br t, 2 FH = 41.0 Hz, CFH). 31 P NMR (C6D6, 162 MHz, 298 K): dR 16.98 (br).

[0077] Throughout the description and claims of this specification, the words“comprise’ and“contain” and variations of them mean“including but not limited to”, and they are not