PROCESS FOR THE RECYCLING OF ORGANOPHOSPHATES

Description

[0001] Phosphorus is essential as a molecular building block for all life forms, is a central component in global food production and has countless applications in industry (see: W. Schipper, Eur. J. Inorg. Chem. 2014, 1567) as well as in the areas of basic and application-oriented research in universities and research institutes.

[0002] Against this background, the current depletion and exploitation of available phosphorus resources is extremely worrying. Phosphorus resources are already considered critical raw materials by the European Commission (see: European Commission, Report of the Ad hoc Working Group on defining critical raw materials: Report on Critical Raw Materials for the EU Ref. Ares, 2015, 1819503 - 29 / 04 / 2015). .Furthermore, current synthesis methods for the preparation of most phosphorus compounds are resource-inefficient, energy-intensive, and require hazardous and toxic reagents (see: a) Emsley, J. The 13th Element: The Sordid Tale of Murder, Fire, and Phosphorus; John Wiley & Sons, Inc.: New York, 2000). ; b) H. Diskowski, T. Hofmann, "Phosphorus," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, 2000 ); c) K. Schrödter et al., "Phosphoric Acid and Phosphates," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, Weinheim, Germany, 2008 ); d) O. Gantner, W. Schipper, JJ Weigand, in Sustainable Phosphorus Management, 1st ed. (Eds.: RW Scholz, AH Roy, FS Brand, D. Hellums, AE Ulrich), Springer Netherlands, 2014 ; e) H. Ohtake, S. Tsuneda, Phosphorus Recovery and Recycling, Springer, Singapore, 2018).

[0003] The natural, but non-renewable, resource of all phosphorus compounds is phosphate rock such as apatite (Ca₅(PO₄)₃(F, OH, Cl)). Here, phosphorus exists in its most stable oxidation state +V as phosphate (PO₄³⁻).

[0004] In this context, we speak of primary phosphorus resources. Secondary phosphorus resources are those that are made available through recycling.

[0005] The vast majority of industrially relevant phosphorus-containing products, such as flame retardants, pharmaceuticals, fertilizers, pesticides, plasticizers, and food or drug additives, etc., exhibit the central phosphorus atom in its most stable oxidation state +V (see: a) Emsley, J. The 13th Element: The Sordid Tale of Murder, Fire, and Phosphorus; John Wiley & Sons, Inc.: New York, 2000). ; b) H. Diskowski, T. Hofmann, "Phosphorus," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, 2000); c) K. Schrödter et al., "Phosphoric Acid and Phosphates," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, Weinheim, Germany, 2008 ); JL Jones, YG Yingling, IM Reaney, P. Westerhoff, MRS Bull. 2020, 45, 7). These phosphorus(V) compounds can be classified according to the number of oxygen atoms bonded to the phosphorus atom, i.e., phosphates (PO₄³⁻), phosphonates (RPO₃²⁻), phosphinates (R₂PO₂²⁻), and phosphine oxides (R₃PO₄).

[0006] The majority of phosphate minerals mined today are used for the synthesis of phosphoric acid (H₃PO₄) for the fertilizer industry. This synthesis is usually carried out using the so-called wet process. In this process, raw phosphate is digested with mineral acids (sulfuric, hydrochloric, or nitric acid). This process generates large quantities of byproducts.

[0007] Alternatively, phosphoric acid can be obtained from the electrothermal reduction of phosphate rock to white phosphorus (P₄). White phosphorus is the most important industrial source of phosphorus for food production, as well as for pharmaceutical, agricultural, and numerous other industrial applications. This involves the combustion of white phosphorus (P₄) to phosphorus pentoxide (P₄O₁₀) followed by hydrolysis (so-called thermal phosphoric acid).

[0008] With the exception of the comparatively inferior phosphoric acid (H 3 PO 4), which is obtained from the wet process mentioned above, the synthetically relevant phosphorus is reduced to P 4 in the thermal process and from there either oxidized to P 4 O 10, chlorinated to PCl 3, or oxychlorinated to OPCl 3.

[0009] These three phosphorus compounds (P₄O₁₀, PCl₃, OPCl₃) represent the most important phosphorus sources of synthetic relevance (see: a) Emsley, J. The 13th Element: The Sordid Tale of Murder, Fire, and Phosphorus; John Wiley & Sons, Inc.: New York, 2000). ; b) H. Diskowski, T. Hofmann, "Phosphorus," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, 2000 ); c) K. Schrödter et al., "Phosphoric Acid and Phosphates," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, Weinheim, Germany, 2008 ); d) O. Gantner, W. Schipper, JJ Weigand, in Sustainable Phosphorus Management, 1st ed. (Eds.: RW Scholz, AH Roy, FS Brand, D. Hellums, AE Ulrich), Springer Netherlands, 2014 ; e) H. Ohtake, S. Tsuneda, Phosphorus Recovery and Recycling, Springer, Singapore, 2018 ).

[0010] Among the various intermediates of the subsequent synthesis steps, the most important source of phosphorus(III) is phosphorus trichloride (PCl₃). This is a corrosive, toxic, and volatile liquid. Phosphorus trichloride is used in subsequent transformation reactions such as hydrolysis, alcoholysis, and salt metathesis to obtain industrially important phosphorus chemicals as well as fine chemicals for academic use. In these transformation reactions, the chlorine atoms of PCl₃ are accepted as waste in the form of salt or corrosive gases (e.g., HCl), which contradicts modern and energy-efficient utilization (see: a) Emsley, J. The 13th Element: The Sordid Tale of Murder, Fire, and Phosphorus; John Wiley & Sons, Inc.: New York, 2000). ; b) H. Diskowski, T. Hofmann, "Phosphorus," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, 2000 );c) K. Schrödter et al., "Phosphoric Acid and Phosphates," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, Weinheim, Germany, 2008 ); d) O. Gantner, W. Schipper, JJ Weigand, in Sustainable Phosphorus Management, 1st ed. (Eds.: RW Scholz, AH Roy, FS Brand, D. Hellums, AE Ulrich), Springer Netherlands, 2014 ; e) H. Ohtake, S. Tsuneda, Phosphorus Recovery and Recycling, Springer, Singapore, 2018).

[0011] The final steps in the formation of industrially relevant oxyphosphorus compounds include alcoholysis or hydrolysis, the Arbuzov reaction, or the Grignard reaction. The relevant reaction steps are shown in Scheme 1 below.

[0012] These reactions generate large quantities of waste. Furthermore, current phosphorus chemistry consumes enormous amounts of energy to first reduce the non-renewable raw material phosphate (PO43-3) (P4), then to chlorinate it (PCl3) or reoxidize it (P4O10, POCl3).

[0013] In summary, the current processing of phosphate ore via electrothermal processes followed by oxidation, chlorination, or oxychlorination is extremely energy-intensive and produces large quantities of waste. The phosphate ore is first reduced to P₄ in a very complex process, and this is then converted into the basic chemicals P₄O₁₀, PCl₃, and OPCl₃. Phosphorus trichloride (PCl₃) and phosphoryl chloride (OPCl₃) are corrosive, toxic, and volatile liquids. These compounds are used in subsequent transformation reactions such as hydrolysis, alcoholysis, and salt metathesis to obtain phosphorus chemicals and fine chemicals for academic and pharmaceutical applications. Ultimately, a large proportion of the chlorine atoms produced during the chlorination of P₄ with chlorine gas end up in salt waste without any commercial value.

[0014] The known processes are therefore particularly energy-intensive, difficult to handle due to the use of corrosive, toxic, and volatile liquids or gases, and produce large quantities of waste. This remains one of the biggest problems in phosphorus chemistry (see: a) Emsley, J. The 13th Element: The Sordid Tale of Murder, Fire, and Phosphorus; John Wiley & Sons, Inc.: New York, 2000). ; b) H. Diskowski, T. Hofmann, "Phosphorus," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, 2000 ); c) K. Schrödter et al., "Phosphoric Acid and Phosphates," Ullmann's Encyclopedia of Industrial Chemistry (Wiley, Weinheim, Germany, 2008 ); d) O. Gantner, W. Schipper, JJ Weigand, in Sustainable Phosphorus Management, 1st ed. (Eds.: RW Scholz, AH Roy, FS Brand, D. Hellums, AE Ulrich), Springer Netherlands, 2014 ; e) H. Ohtake, S. Tsuneda, Phosphorus Recovery and Recycling, Springer, Singapore, 2018 ).

[0015] There is therefore a great need for reaction processes that are able to overcome at least one of the disadvantages mentioned above.

[0016] In this context, Cummins and colleagues, starting from tetrabutylammonium trimetaphosphate ([ n Bu 4 N] 3 [P 3 O 9 ]), a synthesis to bis(trichlorosilyl)phosphide as the tetrabutylammonium salt ([ n Bu 4 N][(SiCl 3 ) 2 P]) is developed, from which a number of other relevant phosphorus chemicals can be synthesized. For this purpose, tetrabutylammonium trimetaphosphate ([ n Bu 4 N] 3 [P 3 O 9 ]) in a steel reactor in Neat Trichlorosilane (HSiCl₃; boiling point 32 °C) reacts at 100 °C for 72 h. This yields the salt [ n Bu 4 N][(SiCl 3 ) 2 P] in 65% yield (see: MB Geeson, CC Cummins, Science, 2018, 359, 1383). Disadvantages of this method are: a) the cation exchange of sodium (Na +< ) to tetrabutylammonium ([ nBu 4 N] +< ), to increase the solubility of [P 3 O 9 ] 3-< , b) the reaction with the pyrophoric, corrosive and toxic liquid HSiCl 3 (boiling point 32 °C), which c) is carried out under hydrothermal conditions (100 °C) in a steel reactor, and d) the long reaction time of 72 h.

[0017] Nevertheless, this approach offers an alternative and laboratory-scale feasible way to synthesize phosphorus chemicals from metaphosphates [P3O9]3-<. According to Cummins et al., this should encourage the exploration of alternative methods (see: MB Geeson, CC Cummins, ACS Cent. Sci. 2020, 6, 848).

[0018] The invention disclosed in EP 4 183 742 A1 already solves several of the aforementioned problems by providing a process that allows the desired oxyphosphorus compounds in the +V oxidation state to be obtained directly from a so-called phosphate compound (e.g., phosphate (PO₄³⁻) or phosphoric acid (H₃PO₄)) without a prior change of oxidation state. A key component is the synthesis of a nitrogen-containing phosphorus(V) precursor, which can be reacted with suitable nucleophiles to give the desired oxyphosphorus compounds, such as organophosphates (phosphoric acid esters). This nitrogen-containing phosphorus(V) precursor is already known; however, its synthesis does not meet the stated requirements (see P. Rovnanik, L. Kapiĉka, J. Taraba, M. Ĉerník, Inorganic chemistry 2004, 43,2435). According to the definition given in the aforementioned patent application, the phosphate compound contains a phosphate that includes at least one phosphorus atom in the +V oxidation state, covalently bonded to four oxygen atoms, and consists only of phosphorus and oxygen atoms. The term phosphate compound describes all salts and acids obtainable by (partial) protonation of the phosphates falling under the term phosphate, but also phosphorus pentoxide. The nitrogen-containing phosphorus(V) precursor is produced by reacting a phosphate compound (e.g., H₃PO₄) with an oxygen acceptor (e.g., trifluoromethanesulfonic anhydride) in the presence of a Lewis base capable of coordination via a nitrogen atom (e.g., pyridine). In this reaction, one oxygen ion (O₂⁻) is formally eliminated twice per phosphorus atom and accepted by the oxygen acceptor.The two free coordination sites on the phosphorus atom are occupied by two equivalents of the Lewis base, forming the nitrogen-containing phosphorus(V) precursor.

[0019] A. Osumah, R. Krishnamurthy, ChemBioChem., 2021, 22, 3001-3009 is a review article on the synthesis of the diamidophosphate anion ([O₂P(NH₂)₂]⁻) from phosphoryl chloride (OPCl₃) or trimetaphosphate ([P₃O₉]⁻), with the synthetic routes involving the use of aqueous ammonia solutions. The use of ([O₂P(NH₂)₂]⁻) as a phosphorylation reagent of sugar derivatives (e.g., inositol or nucleosides) is described, but in aqueous solutions and with low selectivity. The selectivity of the phosphorylations can be increased by the addition of imidazole or by using ([O 2 P(NMe 2 ) 2 ] -< ) in NMP (N-methyl-2-pyrrolidone) and dimethyltin dichloride (Me 2 SnCl 2 ) as a catalyst.

[0020] P. Rovnanik, L. Kapiĉka, J. Taraba, M. Ĉerník, Inorganic chemistry, 2004, 43 References 2435-2442 describe the dismutation of the two phosphoryl halides OPCl₃ and OPBr₃ to [(DMAP)₂PO₂]⁺ and [(Pyr)₂PO₂]⁺ as chloride and bromide salts, respectively, using the bases 4-dimethylaminopyridine (DMAP) and pyridine (Pyr). The stoichiometrically occurring byproducts are the halogenophosphorans PCl₅ and PBr₅.

[0021] E. Thilo, Angew. Chem. Int. Ed., 1965, 4, 1061-1071, is a review article on condensed phosphates, such as metaphosphates, polyphosphates, and ultraphosphates, their composition, properties, and interactions. Various condensed phosphates can be interconverted, with cyclic phosphates (metaphosphates) linked by PO₃-- anions being obtained by thermal dehydration. Metaphosphates can be opened by various nucleophiles, such as OH--, F--, NH₂--, and NR₂--, to give peroxotriphosphate, fluorotriphosphate, and amidotriphosphate. With an excess of NH₃, pyrophosphate ([P₂O₇]⁴--) and diamidomonophosphate ([O₂P(NH₂)₂]⁻-) are formed.

[0022] W. Feldmann, E. Thilo, Z. Anorg. Allg. Chem., 1964, 328, 113-126 describes the reactions of trimetaphosphate ([P₃O₉]³⁻) and tetrametaphosphate ([P₄O₁₂]⁴⁻) with aqueous ammonia solutions to form the open-chain compounds amidotriphosphate and amidotetraphosphate. After some time, an equilibrium is established, so that the cyclic metaphosphates are regenerated. Further addition of ammonia to the open-chain amidotriphosphate leads to the formation of pyrophosphate ([P₂O₇]⁴⁻) and diamidophosphate ([O₂P(NH₂)₂]⁻).

[0023] Regarding secondary phosphorus resources, it must be noted that synthesis routes from recycled phosphorus materials for the production of valuable phosphorus chemicals are either unknown or of very minor importance. This is also due to the lack or absence of chemical and nuclear-economic utilization strategies.

[0024] Rather, many phosphorus compounds in industry are generally not chemically recycled after use, but instead stored in landfills within the respective materials, used as fill material, or in some cases, thermally recovered, i.e., incinerated (see D. Lucas et al. Environ. Eng. Sci. 2018, 35, 573). This further exacerbates the scarcity of phosphorus resources. For example, phosphate compounds used as flame retardant additives in polymers (TEP, triethyl phosphate; or TCPP, tris(1-chloro-2-propyl) phosphate) or extraction agents for metal recovery (TBP, tributyl phosphate; D2EHPA, bis(2-ethylhexyl) phosphate) are generally not chemically recycled, but instead stored in landfills within the respective materials, used as fill material, or thermally recovered.

[0025] Recycling phosphorus-containing waste materials into valuable phosphorus chemicals, which is advantageous from both a chemical and an atomic economic point of view, is completely unknown to date.

[0026] There is therefore a great need for reaction processes that are able to utilize secondary phosphorus resources and that are also acceptable in terms of energy and chemical input.

[0027] The present invention solves several of the above-mentioned problems by providing a method that allows the desired oxyphosphorus compounds in the +V oxidation state to be obtained directly from organophosphates (phosphoric acid esters) without a prior change of oxidation state.

[0028] This involves the direct conversion of the secondary phosphorus resource (phosphoric acid esters) into the desired oxyphosphorus compounds while maintaining the +V oxidation state of the phosphorus atom used.

[0029] Accordingly, the process according to the invention provides a new route for the synthesis of industrially and academically relevant oxyphosphorus compounds from secondary phosphorus resources. This saves time, energy, costs, chemical waste, and hazardous reagents (such as Cl₂ or HSiCl₃). Furthermore, scarce primary phosphorus resources are conserved because a portion of the secondary phosphate resources (phosphoric acid esters) is not stored unused in the respective materials, used as filler material, or even incinerated, but is chemically recycled.

[0030] The present invention thus makes it possible to offer an atom- and energy-efficient solution for the production of oxyphosphorus compounds of the oxidation state +V directly from phosphoric acid esters.

[0031] A central component of the present invention is the synthesis of nitrogen-containing phosphorus(V) precursors. These can be reacted with suitable nucleophiles to form the desired oxyphosphorus compounds, such as organophosphates (phosphoric acid esters) and phosphinates.

[0032] The present invention is therefore directed to a process for the synthesis of nitrogen-containing phosphorus(V) precursors of formula (I), the procedure comprises the following steps in the specified order: a) Provision of a phosphoric acid ester; b) Reaction of the phosphoric acid ester from step a) with an oxygen acceptor in the presence of a Lewis base LN₂ capable of coordination via a nitrogen atom, wherein the oxygen acceptor is the cation of a sulfonic anhydride according to formula (II) and the sulfonic anhydride is according to formula (III), wherein according to step b) alternatively either b1) the phosphoric acid ester from step a) is reacted with a sulfonic acid anhydride according to formula (III) in the presence of a Lewis base LN, or b2) the phosphoric acid ester from step a) is reacted with the reaction product of a sulfonic acid anhydride according to formula (III) with a Lewis base LN, wherein said reaction product is according to formula (IV) wherein R is an aliphatic or aromatic hydrocarbon residue which may contain heteroatoms, wherein the number of carbon atoms of residue R is from 1 to 21, and the heteroatoms are selected from the group consisting of oxygen, nitrogen, fluorine, chlorine, bromine, iodine, and mixtures thereof, wherein the Lewis base LN, capable of coordination via a nitrogen atom, is a nitrogen-containing heteroaromatic compound containing a six-membered heteroaromatic ring containing a coordination-capable nitrogen atom, wherein the number of carbon atoms of the Lewis base LN is from 4 to 19, wherein the phosphoric acid ester from step a) is according to one of the formulas (Va), (Vb), and (Vc). where R Alk< is a hydrocarbon residue which may contain heteroatoms.

[0033] The oxygen acceptor of formula (II) that is effective in the process for the synthesis of nitrogen-containing phosphorus(V) precursors of formula (I) according to step b) is accordingly used either in the form of a sulfonic anhydride of formula (III), or alternatively in the form of the reaction product according to formula (IV), which has been previously prepared by reacting a sulfonic anhydride of formula (III) with a Lewis base LN. In both cases, the effective oxygen acceptor of formula (II) is released in situ during the reaction according to step b) and reacts with the phosphoric acid ester from step a) in the presence of a Lewis base LN.

[0034] The resulting nitrogen-containing phosphorus(V) precursor of formula (I) is a singly positively charged cation and can be isolated with a suitable counterion.

[0035] The process for the synthesis of nitrogen-containing phosphorus(V) precursors of formula (I) according to the present invention can accordingly be described by means of the following general reaction equations:

[0036] In the reaction equations shown, a phosphorus atom is deoxygenated twice; that is, formally, a total of two oxygen ions (O²⁻) per phosphorus atom are eliminated and accepted by the oxygen acceptor. The substituent R, Alk or H, is transferred to the Lewis base LN. The two vacant coordination sites on the phosphorus atom are occupied by two equivalents of the Lewis base LN, forming the nitrogenous phosphorus(V) precursor of formula (I). The coordination of the Lewis base LN occurs via the lone pair of electrons on a nitrogen atom, forming two phosphorus-nitrogen bonds. In the case of the tryster, three equivalents of a pyridinium or ammonium cation [LN₂-R₂Alk₁₀]⁺ are formed; in the case of the diester, two equivalents of a pyridinium or ammonium cation [LN₂-R₂Alk₁₀]⁺ and one equivalent of a pyridinium or ammonium cation [LN₂-H]⁺ are formed; and in the case of the monoester, one equivalent of a pyridinium or ammonium cation [LN₂-H]⁺ is formed.Ammonium cation [LN -R Alk< ] +< and two equivalents of a pyridinium or Ammonium cation [LN-H] +< .

[0037] As mentioned above, in the process for the synthesis of nitrogen-containing phosphorus(V) precursors of formula (I) according to the present invention, the phosphoric acid ester from step a) is obtained according to one of the formulas (Va), (Vb) and (Vc), wherein R Alk< is a hydrocarbon residue which may contain heteroatoms.

[0038] In the case of formulas (Va) and (Vb), the individual hydrocarbon residues R Alk< can be identical or different.

[0039] Regardless, in the case of formula (Va) two or three hydrocarbon residues R Alk< , in the case of formula (Vb) two hydrocarbon residues R Alk< , can together form a bridge between oxygen atoms bonded to the same phosphorus atom.

[0040] The nature of the hydrocarbon residue RAlk, such as the number of carbon atoms, the number and type of heteroatoms, the degree of saturation, and the presence, number, and extent of aliphatic and aromatic groups, is arbitrary. If a phosphoric acid ester according to one of formulas (Va), (Vb), and (Vc) can be prepared, which is not the subject of the present invention, it can also be provided in step a) of the process for synthesizing nitrogenous phosphorus(V) precursors of formula (I) according to the present invention, and can also be converted to a nitrogenous phosphorus(V) precursor of formula (I) according to step b) of the process for synthesizing nitrogenous phosphorus(V) precursors of formula (I) according to the present invention.

[0041] In common phosphoric acid esters that can be used here, the number of carbon atoms of each R Alk< is from 1 to 50 or from 1 to 25 or from 1 to 12 or from 1 to 8 or from 1 to 4.

[0042] In common and usable phosphoric acid esters, the number of carbon atoms of all R Alk< together in one of the formulas (Va), (Vb) or (Vc) is from 1 to 50 or from 1 to 25 or from 1 to 18 or from 1 to 12.

[0043] In common and usable phosphoric acid esters, the heteroatoms of R Alk< are selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine.

[0044] In common and usable phosphoric acid esters, the heteroatoms of R Alk< are selected from the group consisting of oxygen, nitrogen and fluorine.

[0045] In common phosphoric acid esters that can be used here, the residue R Alk< contains no further heteroatoms.

[0046] In common and applicable phosphoric acid esters, the number of carbon atoms of each R Alk< is from 1 to 12, the number of carbon atoms of all R Alk< together in one of the formulas (Va), (Vb) or (Vc) is from 1 to 25, and the heteroatoms of R Alk< are selected from the group consisting of oxygen, nitrogen and fluorine.

[0047] In common and applicable phosphoric acid esters, the number of carbon atoms of each R Alk< is from 1 to 8, the number of carbon atoms of all R Alk< together in one of the formulas (Va), (Vb) or (Vc) is from 1 to 25, and the heteroatoms of R Alk< are selected from the group consisting of oxygen, nitrogen and fluorine.

[0048] In common and usable phosphoric acid esters, the number of carbon atoms of each R Alk< is from 1 to 8, the number of carbon atoms of all R Alk< together in one of the formulas (Va), (Vb) or (Vc) is from 1 to 25, and the residue R Alk< contains no further heteroatoms.

[0049] In common and usable phosphoric acid esters, the number of carbon atoms of each R Alk< is from 1 to 4, the number of carbon atoms of all R Alk< together in one of the formulas (Va), (Vb) or (Vc) is from 1 to 12, and the residue R Alk< contains no further heteroatoms.

[0050] Common and usable phosphoric acid esters include, in particular, those that can be obtained by esterification of monohydric alcohols, diols, polyols, sugar alcohols and sugars, including nucleosides.

[0051] According to the present invention, it is preferred that a carbon atom of a hydrocarbon residue R Alk< in one of the formulas (Va), (Vb) or (Vc), which is directly bonded to the oxygen atom of the ester bond of the phosphoric acid ester (C-1), is bonded to three further atoms. It is here referred to as such a carbon atom (C-1) having a saturated aliphatic state or being sp3< hybridized. In this context, it is further preferred that two or three of these three further atoms are hydrogen atoms.

[0052] In this context, according to the present invention, it is further preferred that the carbon atom (C-1) in all hydrocarbon residues R Alk< has a saturated aliphatic state or that it is sp 3< hybridized; it is further preferred that two or three of the three other atoms are hydrogen atoms. This applies accordingly to hydrocarbon residues R Alk< in each of the formulas (Va), (Vb) or (Vc).

[0053] In this context, according to the present invention, it is further preferred that each of the hydrocarbon residues R Alk< in one of the formulas (Va), (Vb) or (Vc) is a saturated aliphatic hydrocarbon residue.

[0054] In this context, according to the present invention, it is further preferred that each of the hydrocarbon residues R Alk< in one of the formulas (Va), (Vb) or (Vc) is a saturated aliphatic hydrocarbon residue that does not contain any heteroatoms.

[0055] As defined above, the phosphorus atom of the phosphoric acid ester is doubly deoxygenated, and the two free coordination sites on the phosphorus atom are occupied by two equivalents of the Lewis base LN to form the nitrogenous phosphorus(V) precursor of formula (I). It follows that the phosphoric acid ester must be reacted with at least two equivalents of a sulfonic anhydride according to formula (III) in the presence of at least two equivalents of a Lewis base LN, or alternatively, the phosphoric acid ester must be reacted with at least two equivalents of the reaction product according to formula (IV).

[0056] The respective equivalents refer to the equivalent amount of phosphorus atoms in the phosphoric acid ester. The amount of substance of the reactants must, of course, be adjusted to the amount of phosphorus atoms in the phosphoric acid ester.

[0057] The sulfonic anhydride is usually added in at least half an equivalent and at most in ten equivalents.

[0058] The Lewis base LN is usually added in at least two equivalents, preferably in five equivalents, and at most in ten equivalents. When using a solvent that meets the definition of a Lewis base LN, without adding any additional Lewis base LN, the equivalent amount of Lewis base LN is naturally higher, usually at most 100 equivalents.

[0059] In the alternative variant, the reaction product according to formula (IV) is usually added in at least two equivalents and at most in ten equivalents. Preferably, in this variant, a further three equivalents of Lewis base LN are added.

[0060] According to a preferred embodiment of the present invention, the reaction of the phosphoric acid ester with an oxygen acceptor is carried out in the presence of at least five equivalents of a Lewis base LN₂. The reaction of the phosphoric acid ester with an oxygen acceptor is usually carried out in the presence of at most 100 equivalents of a Lewis base LN₂.

[0061] As mentioned above, the R group of the sulfonic anhydride of formula (III) (and correspondingly the R group in formulas (II) and (IV)) is an aliphatic or aromatic hydrocarbon residue that may contain heteroatoms, the number of carbon atoms ranging from 1 to 21. If present, the heteroatoms are selected from the group consisting of oxygen, nitrogen, fluorine, chlorine, bromine, iodine, and mixtures thereof. Apart from these heteroatoms, the R group contains no other heteroatoms.

[0062] Preferably, the heteroatoms - if present - are selected from the group consisting of oxygen, nitrogen, fluorine, chlorine, bromine, and iodine, that is, the residue R does not contain heteroatoms of different atomic numbers.

[0063] Preferably, the number of heteroatoms in the residue R is not higher than three.

[0064] In the case that R is an aliphatic hydrocarbon residue, the number of carbon atoms is preferably from 1 to 11, and more preferably from 1 to 6. Independently of this, it is further preferred that any heteroatoms present are selected from the group consisting of oxygen, nitrogen, and fluorine, and mixtures thereof, and particularly preferred that any heteroatoms present are selected from the group consisting of oxygen, nitrogen, and fluorine, i.e., the residue R does not contain heteroatoms of different atomic numbers. In this context, it is particularly preferred that the residue R is selected from the group consisting of C1-C6 alkyl, cyclohexyl, C1-C6 alkoxy, trifluoromethoxy, trifluoromethyl, C2F5, C2F4H, C3F7, C3F6H, C4F9, C4F8H, C5F11 and C5F10H. The most preferred aliphatic hydrocarbon residue R in this context is trifluoromethyl (CF3).

[0065] In the case that R is an aromatic hydrocarbon residue, R is preferably defined by the following formula (IIIa): wherein the residues R1<, R2<, R3<, R4<, and R5< are independently selected from the group consisting of hydrogen, C1-C3 alkyl, C1-C3 alkoxy, fluorine, chlorine, bromine, iodine, the nitro group, and trifluoromethyl. In this context, the residues R1<, R2<, R3<, R4<, and R5< are particularly preferably selected independently from the group consisting of hydrogen, methyl, methoxy, fluorine, chlorine, the nitro group, and trifluoromethyl. In this preferred group, the residues R1<, R2<, R3<, R4<, and R5< are further preferably selected from the following combinations: R1< , R2< , R3< , R4< , R5< = H, R1< , R2< , R3< , R4< , R5< = CH3 , R1< , R2< , R3< , R4< = H and R5< = CH3 , R1< , R2< , R3< , R4< = H and R5< = F, R1< , R2< , R3< , R4< = H and R5< = Cl, R1< , R2< , R3< , R4< = H and R5< = OCH3 , R1< , R2< , R3< , R4< = H and R5< = NO2 , R1< , R2< , R 3< , R 4< = H and R 5< = CF 3 , R 1< , R 2< , R 4< = H and R 3< , R 5< = CH 3 , R 2< , R 4< = H and R 1< , R 3< , R 5< = CH 3 , R 2< , R 3< , R 5< = H and R 1< , R 4< = CH 3 , or R 1< , R 2< , R 4< , R 5< = H and R 3< = CH 3 .

[0066] The most preferred combination in this context is: R 1< , R 2< , R 4< , R 5< = H and R 3< = CH 3 .

[0067] The most preferred sulfonic anhydride of formula (III) with an aliphatic hydrocarbon residue R is accordingly trifluoromethanesulfonic anhydride (Tf 2 O) and accordingly the most preferred cation of a sulfonic anhydride according to formula (II) with an aliphatic hydrocarbon residue R is the trifluoromethanesulfonic anhydride F 3 CSO 2 +< (Tf +< ).

[0068] The most preferred sulfonic anhydride of formula (III) with an aromatic hydrocarbon residue R is accordingly p-toluenesulfonic anhydride and accordingly the most preferred cation of a sulfonic anhydride according to formula (II) with an aromatic hydrocarbon residue R is the tosyl cation H 3 CC 6 H 4 -SO 2 +< (Ts +< ).

[0069] The most preferred sulfonic anhydride of formula (III) is trifluoromethanesulfonic anhydride (Tf 2 O) and accordingly the most preferred cation of a sulfonic anhydride according to formula (II) is the triflyl cation F 3 CSO 2 +< (Tf +< ).

[0070] In the most preferred method according to the present invention, two equivalents of triflyl cation deoxygenate one phosphorus atom of the phosphoric acid ester twice to form two equivalents of trifluoromethanesulfonate (triflate, OTf -< ).

[0071] The triflyl cation is therefore the most preferred oxygen acceptor in the process according to the present invention.

[0072] The triflylk cation can be used in the process in the form of trifluoromethanesulfonic anhydride.

[0073] As an alternative to using trifluoromethanesulfonic anhydride, trifluoromethanesulfonic anhydride, Tf₂O, can first be reacted with the Lewis base LN₂. The reaction product contains the triflyl cation bound to the Lewis base LN₂ as the salt of the triflate anion, OTf⁻. Tf 2 O + L N → L N − Tf OTf

[0074] The reaction schemes of the particularly preferred embodiments using trifluoromethanesulfonic anhydride are shown below:

[0075] The reaction schemes of the alternative particularly preferred embodiment using [LN-Tf][OTf] are shown below:

[0076] As mentioned above, the Lewis base LN is capable of coordination via a nitrogen atom and is a nitrogen-containing heteroaromatic compound containing a six-membered heteroaromatic ring, which contains a nitrogen atom capable of coordination, and where the number of carbon atoms of the Lewis base LN is from 4 to 19.

[0077] The Lewis base LN can contain further heteroatoms selected from the list consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, bromine, iodine, and mixtures thereof. Apart from the heteroatoms mentioned, the Lewis base LN contains no other heteroatoms.

[0078] The Lewis base LN preferably contains one or two of the aforementioned six-membered heteroaromatic rings.

[0079] The Lewis base LN preferably contains one or two nitrogen atoms.

[0080] Preferably, the Lewis base LN contains one or two six-membered heteroaromatic rings, and the Lewis base LN contains one or two coordinating nitrogen atoms per six-membered heteroaromatic ring in the six-membered heteroaromatic ring, and the Lewis base LN contains a total of one or two nitrogen atoms.

[0081] The Lewis base LN contains - if oxygen atoms are present - preferably one or two oxygen atoms.

[0082] The oxygen atoms of the Lewis base LN - if present - remain a preferred component of methoxy or ethoxy groups.

[0083] The Lewis base LN preferably contains no more than two methoxy or ethoxy groups.

[0084] The Lewis base LN contains - if these heteroatoms are present - preferably one, two, three or four heteroatoms selected from the group consisting of fluorine, chlorine, bromine, iodine, and mixtures thereof.

[0085] The Lewis base LN contains - if these heteroatoms are present - preferably one, two, three or four heteroatoms selected from the group consisting of fluorine, chlorine, bromine, iodine, that is to say, the Lewis base LN does not contain heteroatoms of this group with different atomic numbers.

[0086] The Lewis base LN preferably contains no sulfur.

[0087] The Lewis base LN particularly preferably contains independently of one or two nitrogen atoms, zero, one or two oxygen atoms, zero, one, two, three or four heteroatoms selected from the group consisting of fluorine, chlorine, bromine, and iodine, and contains no further heteroatoms.

[0088] The Lewis base LN is preferably selected from the group consisting of pyridines, picolines, lutidines, collidines, bipyridines, pyridazines, pyrimidines, pyrazines, quinolines and isoquinolines.

[0089] The Lewis base LN is further preferably selected from the following substances or classes of substances: pyridine, mono- or polymethyl-substituted pyridines such as pentamethylpyridine, picolins, lutidines, and collidines, mono-alkyl-substituted pyridines, wherein the alkyl group contains between 2 and 10 carbon atoms, mono-phenyl-substituted pyridines, aminopyridines, dimethylaminopyridines, mono- or di-methoxy- or ethoxy-substituted pyridines, and mono-, di- or tri-halogen-substituted pyridines.

[0090] Bipyridine, monomethyl-substituted bipyridines, monohalogen-substituted bipyridines, dimethyl-substituted bipyridines, dihalogen-substituted bipyridines, tetramethyl-substituted bipyridines, and tetrahalogen-substituted bipyridines.

[0091] Diazines such as pyridazine, pyrimidine and pyrazine, monomethyl-substituted pyridazines, monohalogen-substituted pyridazines, dimethyl-substituted pyridazines, dihalogen-substituted pyridazines, trimethyl-substituted pyridazines, trihalogen-substituted pyridazines, quadruple-methyl-substituted pyridazine, quadruple-halogen-substituted pyridazine, monomethyl-substituted pyrimidines, monohalogen-substituted pyrimidines, dimethyl-substituted pyrimidines, dihalogen-substituted pyrimidines, trimethyl-substituted pyrimidines, trihalogen-substituted pyrimidines, quadruple-methyl-substituted pyrimidine, quadruple-halogen-substituted pyrimidine, monomethyl-substituted pyrazines, monohalogen-substituted pyrazines, dimethyl-substituted methyl-substituted pyrazines, di-halogenated pyrazines, triple-methyl-substituted pyrazines, triple-halogenated pyrazines,tetramethyl-substituted pyrazine, as well as tetrahalogen-substituted pyrazine,

[0092] Quinolines such as quinoline, monomethyl-substituted quinolines, dimethyl-substituted quinolines, trimethyl-substituted quinolines, tetramethyl-substituted quinolines, monohalogen-substituted quinolines, where substitution with one to six methyl groups may be present simultaneously, and sevenfold methyl-substituted quinoline.

[0093] Isoquinolines such as isoquinoline, monomethyl-substituted isoquinolines, dimethyl-substituted isoquinolines, monohalogen-substituted isoquinolines, where substitution with one to six methyl groups may be present simultaneously, and sevenfold methyl-substituted isoquinoline.

[0094] The number of carbon atoms of the Lewis base LN is preferably from 4 to 16, further preferably from 4 to 12, and particularly preferably from 5 to 9.

[0095] The Lewis base LN still preferably contains one or two nitrogen atoms and no other heteroatoms.

[0096] According to a particularly preferred embodiment of the present invention, the Lewis base LN is selected from the group consisting of pyridine, 4-dimethylaminopyridine, and mixtures thereof.

[0097] The Lewis base LN can also form during the reaction if, as described above, the Lewis base LN is reacted with a sulfonic anhydride, most preferably trifluoromethanesulfonic anhydride, Tf₂O, prior to carrying out the process according to the present invention. In this alternative, the reaction product is [LN₂-Tf][OTf], which is then used in the process according to the present invention. As soon as the oxygen acceptor, the triflyl cation, Tf⁺, reacts to form the triflate anion, OTf⁻, LN₂ is released and can bind to the phosphorus atom of the phosphoric acid ester. The reaction of the phosphoric acid ester with the oxygen acceptor thus also takes place in the presence of a Lewis base LN₂ in this alternative.

[0098] The process according to the present invention can be carried out in solution, in the melt, or as a solid-state reaction.

[0099] In the process according to the present invention, the synthesis is particularly preferably carried out in an aprotic solvent.

[0100] Furthermore, it is particularly preferred that, in the process according to the present invention, no other Lewis bases or nucleophiles are added besides the Lewis base LN. Other Lewis bases or nucleophiles are understood here to be substances that differ from the Lewis base LN defined above. These other Lewis bases or nucleophiles could compete with the Lewis base LN defined above for binding to the phosphorus atom of the phosphoric acid ester and thus hinder, prevent, or reduce the yield of the nitrogenous phosphorus(V) precursor of formula (I) by forming mixtures.

[0101] In this context, those skilled in the art are aware of the requirement to exclude further Lewis bases or nucleophiles from the reaction, as is the case with similar reactions in the prior art. In particular, those skilled in the art will exclude, for example, the following substances from the reaction: water, alcohols, ammonia, amines, imines, azoles, pyrrolines, sulfides, halides, and organometallic reagents.

[0102] Preferably, the solvent is defined as the Lewis base LN, wherein the solvent additionally has a melting point below 20 °C (at normal pressure corresponding to 101325 Pa).

[0103] Pyridine is particularly preferred as a solvent.

[0104] In the case of a solid-state reaction, the reaction is preferably carried out at an elevated temperature, preferably above 100 °C. The temperature will usually be below 200 °C.

[0105] According to a particularly preferred embodiment of the method according to the present invention, the sulfonic anhydride according to formula (III) is trifluoromethanesulfonic anhydride and the Lewis base LN is selected from the group consisting of pyridine, 4-dimethylaminopyridine, and mixtures thereof.

[0106] According to a further particularly preferred embodiment of the process according to the present invention, the sulfonic acid anhydride according to formula (III) is trifluoromethanesulfonic acid anhydride, the Lewis base is LN pyridine or 4-dimethylaminopyridine, and the synthesis is carried out in pyridine as a solvent.

[0107] When pyridine is used as the most preferred solvent in the process according to the present invention, it automatically also acts as the Lewis base LN. However, if the process is carried out with pyridine as the solvent in the presence of 4-dimethylaminopyridine as the Lewis base LN, the nitrogenous phosphorus(V) precursor of formula (I) contains two equivalents of 4-dimethylaminopyridine.

[0108] When using trifluoromethanesulfonic anhydride as the sulfonic anhydride according to formula (III), pyridine or 4-dimethylaminopyridine as the Lewis base LN and pyridine as the solvent, the cation of formula (I) precipitates from the solution with triflate, OTf -< , as the counterion and can be isolated and washed in the usual way.

[0109] The present invention enables a process for the synthesis of oxyphosphorus compounds, wherein the process comprises the following steps in the specified order: c) Synthesis of a nitrogen-containing phosphorus(V) precursor of formula (I) according to the present invention; d) Reaction of the nitrogen-containing phosphorus(V) precursor of formula (I) with a nucleophile.

[0110] Those in the know are familiar with the term nucleophile. Any nucleophile can be used in the process for synthesizing oxyphosphorus compounds.

[0111] The nucleophile is preferably selected from the group consisting of alcohols, ammonia, primary amines, secondary amines, tertiary amines, azoles, organometallic compounds, and fluoride. Fluoride can be used in the usual way as a metal fluoride, such as cesium fluoride. Furthermore, any of the compounds described above in connection with the present invention as Lewis bases (LN) can be used as the nucleophile.

[0112] It is known to those skilled in the art that in such reactions of a nucleophile, it can also be used in its deprotonated form. In the case of alcohols, these are the alkoxides, which can be used in the usual way as metal alkoxides.

[0113] Regarding suitable or preferred compounds that can be used as phosphoric acid esters, as sulfonic anhydride according to formula (III), as Lewis base LN₂, and as solvents in step c) above of the process for the synthesis of oxyphosphorus compounds, reference is made to the corresponding descriptions in connection with the present invention. The same applies to suitable and preferred reaction conditions.

[0114] The nitrogen-containing phosphorus(V) precursor of formula (I) according to the present invention can be isolated and then used in step d) of the process for the synthesis of oxyphosphorus compounds.

[0115] Step d) of the process for the synthesis of oxyphosphorus compounds is preferably carried out in solution or suspension of the reactants in a non-aqueous solvent. Suitable nucleophiles can also be used as solvents. Typical solvents are all common organic solvents (e.g., acetonitrile, nitromethane, tetrahydrofuran, pyridine, dichloromethane) and their mixtures. Those skilled in the art are aware of which other solvents can be used and will be able to identify a suitable solvent for each reactant pair consisting of a nitrogenous phosphorus(V) precursor of formula (I) and a nucleophile. Finding a suitable solvent is part of the fundamental expertise of a person skilled in the art in preparative chemistry.

[0116] One nucleophile that can be used as a solvent is, for example, 2-ethylhexanol.

[0117] As an alternative to isolating the nitrogen-containing phosphorus(V) precursor of formula (I) according to the present invention, the nucleophile according to step d) of the process for the synthesis of oxyphosphorus compounds can also be added to the reaction mixture from step b) of the process of the present invention.

[0118] In this case, both reactions take place in the same reaction vessel. However, it is necessary to wait until the synthesis of the nitrogen-containing phosphorus(V) precursor of formula (I) is complete, i.e., until the reaction equilibrium has been reached or no longer changes. A person skilled in the art knows how to determine this point in time by suitable analytical methods, such as NMR spectroscopy of the reaction solution.

[0119] In a particularly preferred embodiment of the process according to the present invention, the reaction is carried out in pyridine as the solvent, the sulfonic anhydride according to formula (III) is trifluoromethanesulfonic anhydride, and the Lewis base LN is either pyridine as the solvent or 4-dimethylaminopyridine is additionally added as the Lewis base LN. In this particularly preferred embodiment, the product, the salt of the cation of formula (I) with triflate, OTf-<, as the counterion, precipitates from the solution. The progress of the reaction can therefore be recognized by the turbidity of the solution. In a so-called one-pot reaction, the nucleophile can be added to this suspension.

[0120] Depending on whether the nucleophile is deprotonated before or during the reaction, the resulting product can be an anion or a cation, which can be isolated from the reaction solution with a suitable counterion and purified in the usual way.

[0121] If the nucleophile is an alcohol or an alkoxide, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0122] In this way, the corresponding diesters of phosphoric acid are easily accessible. In contrast to the classical synthesis from phosphorus pentoxide and alcohol, the diesters are formed selectively, and therefore no separation of the monoesters and triesters from a product mixture is necessary. In principle, any alcohol or alkoxide is suitable as a nucleophile.

[0123] The RA< residue is a hydrocarbon residue that may contain heteroatoms. Two RA< residues can together form a bridge between two hydroxyl groups, and the alcohol can thus bind to the phosphorus atom as a bridging chelating ligand.

[0124] Preferably, the number of carbon atoms in RA< is between 1 and 50 or between 1 and 25. Furthermore, the heteroatoms are preferably selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Particularly preferably, the residue RA< contains no other heteroatoms besides oxygen, nitrogen, and fluorine, and even more preferably, no other heteroatoms at all.

[0125] Suitable alcohols include monohydric alcohols, diols, polyols, sugar alcohols and sugars, including nucleosides.

[0126] For example, 2-ethylhexanol can be used as a nucleophile. The reaction with two equivalents of 2-ethylhexanol readily yields the industrially important bis(2-ethylhexyl)phosphate (see: data sheet). Bis(2-ethylhexyl) phosphates, 95% (at AlfaAesar, accessed on March 25, 2020 (PDF)). Equally important industrially is the use of 2,2,2-trifluoroethanol as a nucleophile for the analogous synthesis of bis(2,2,2-trifluoroethyl)phosphate (see: a) A. Maruo, S. Yamazaki, Liquid Electrolyte comprising an alkalimetal salt of a phosphate compound, WO-A1-2013 / 002186; b) A. Garsuch, M. Schmidt, R. Schmitz, I. Krossing, P. Eiden, S. Reininger, Inorganic coordination polymers as gelling agents, WO 2015 / 128363 A1). Finally, the process according to the present invention allows the simple conversion of 1,1'-Bi-2-naphthol (BINOL) to BINOL phosphate (see: D. Parmar, E. Sugiono, S. Raja, M. Rueping, Chem. Rev. 2014, 114, 9047).

[0127] If the nucleophile is ammonia, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0128] In this way, diamidophosphate is easily accessible.

[0129] If the nucleophile is a primary amine, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0130] In this way, diamidophosphate is easily accessible.

[0131] In principle, any primary amine or primary amide is suitable as a nucleophile.

[0132] The RB< residue is a hydrocarbon residue that may contain heteroatoms. Two RB< residues can together form a bridge between two amine groups and thus coordinate the amine to the phosphorus atom as a bridging chelating ligand.

[0133] Preferably, the number of carbon atoms in RB< is between 1 and 25 or between 1 and 10. Furthermore preferably, the heteroatoms are selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Particularly preferably, the residue RB< contains no other heteroatoms besides oxygen, nitrogen, and fluorine, and even more preferably, no other heteroatoms at all.

[0134] If the nucleophile is a secondary amine, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0135] In this way, the corresponding diamidophosphates are easily accessible.

[0136] In principle, any secondary amine or secondary amide is suitable as a nucleophile.

[0137] The residue RC< is a hydrocarbon residue that may contain heteroatoms. Two residues RC< can together form a bridge between two amine groups and thus coordinate the amine to the phosphorus atom as a bridging chelating ligand.

[0138] Preferably, the number of carbon atoms in RC< is between 1 and 25 or between 1 and 10. Furthermore, the heteroatoms are preferably selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Particularly preferably, the residue RC< contains no other heteroatoms besides oxygen, nitrogen, and fluorine, and even more preferably, no other heteroatoms at all.

[0139] If the nucleophile is a tertiary amine, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0140] In this way, the corresponding diamoniophosphates are easily accessible.

[0141] In principle, any tertiary amine is suitable as a nucleophile.

[0142] The RD< residue is a hydrocarbon residue that may contain heteroatoms. Two RD< residues can together form a bridge between two amine groups and thus coordinate the amine to the phosphorus atom as a bridging chelating ligand.

[0143] Preferably, the number of carbon atoms in RD< is between 1 and 25 or between 1 and 10. Furthermore, the heteroatoms are preferably selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Particularly preferably, the residue RD< contains no other heteroatoms besides oxygen, nitrogen, and fluorine, and even more preferably, no other heteroatoms at all.

[0144] If the nucleophile is an azole, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0145] In this way, the corresponding diamidophosphates are easily accessible.

[0146] The nucleophile azole is preferably selected from the group consisting of pyrroles, imidazoles, pyrazoles, triazoles and tetrazoles.

[0147] Specifically, the following should be mentioned: Pyrroles such as pyrrole, monoalkyl-substituted pyrroles, dialkyl-substituted pyrroles, trialkyl-substituted pyrroles, tetraalkyl-substituted pyrroles; imidazoles such as 1,3-imidazole, monoalkyl-substituted imidazoles, dialkyl-substituted imidazoles, trialkyl-substituted imidazoles; pyrazoles such as 1,2-pyrazole, monoalkyl-substituted pyrazoles, dialkyl-substituted pyrazoles, trialkyl-substituted pyrazoles; triazoles such as 1,2,3-triazole, 1,2,4-triazole, monoalkyl-substituted triazoles, dialkyl-substituted triazoles; tetrazoles such as tetrazole, monoalkyl-substituted tetrazoles,

[0148] The number of carbon atoms in azoles is preferably from 4 to 24.

[0149] The azoles still preferably contain one to four nitrogen atoms and no other heteroatoms.

[0150] If the nucleophile is an organometallic compound, the reaction can be illustrated according to the procedure for the synthesis of oxyphosphorus compounds as follows:

[0151] In this way, the corresponding phosphinates are easily accessible.

[0152] In principle, any organometallic compound in which the carbon atom reacts nucleophilically is suitable as a nucleophile. This includes organometallic compounds containing metals such as lithium, magnesium, aluminum, zinc, and copper.

[0153] The RE< residue is a hydrocarbon residue that may contain heteroatoms. Two RE< residues can together form a bridge between two carbon atoms and thus coordinate to the phosphorus atom as a bridging chelating ligand.

[0154] Preferably, the number of carbon atoms in RE< is between 1 and 25 or between 1 and 10. Furthermore, the heteroatoms are preferably selected from the group consisting of nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Particularly preferably, the residue RE< contains no further heteroatoms, and even more preferably, no further heteroatoms. Experimental section

[0155] All reactions were carried out in a dried inert gas atmosphere (N2 or Ar) using a glovebox ( Innovative Technology Pure Lab HE, MBraun Unilab) or using the Schlenk technique. Glassware was stored at 150 °C before use or baked under vacuum with a hot air blower. Solvents used were distilled beforehand with suitable drying agents and stored over a molecular sieve. The deuterated solvents were obtained from Merck, Deutero, or Eurisotop and stored over a molecular sieve before use. 1< H NMR, 13< C NMR, 31< P NMR, 19< F NMR

[0156] Nuclear magnetic resonance experiments were performed on the devices AVANCE III HD Nanobay 400 MHz Ultrashield (Resonance frequencies: 1< H = 400.13 MHz, 19< F = 376.50 Hz, 31< P = 161.98 MHz) or AVANCE III HDX 500 MHz Ascend (Resonance frequencies: 1< H = 500.13 MHz, 19< F = 470.59 MHz, 31< P = 202.45 MHz) of the company Bruker and with the software Topspin evaluated. The values ​​of the chemical shift δThese values ​​refer to the external standards tetramethylsilane (1 < H), trichlorofluoromethane (19 < F), or 85% phosphoric acid (31 < P) and are given in ppm, rounded to 1-2 decimal places. Scalar couplings via n Bonds n< J The values ​​are given in Hz, rounded to 1-2 decimal places. The following abbreviations are used to describe the multiplicity: s - singlet, s(br) - wide singlet, d - doublet, t - triplet, q - quartet, m - multiplet. Combinations of these abbreviations are always given in descending order of coupling constants. chemicals

[0157] Chemicals and solvents were sourced from Merck, VWR, Alfa Aesar, Acros Organics, or TCI. Trifluoromethanesulfonic anhydride (Tf₂O) was donated by Solvay. Abbreviations

[0158] Equivalents BINOL1,1'-Bi-2-naphthol D2EHPABis(2-ethylhexyl)phosphate KOtBuPotassium tert-butanolate MeOHMethanol OTf -< Trifluoromethanesulfonate OP(OMe) 3 Trimethylphosphate PhMgBrPhenylmagnesium bromide PyPyridine Tf +< Triflate cation Tf 2 OTrifluoromethanesulfonic anhydride THFTetrahydrofuran Ts 2 O p -Toluenesulfonic anhydride Examples Example 1: Synthesis of (LN ) 2 PO 2 [OTf] (LN = pyridiniumyl) from triethyl phosphate

[0159] Trifluoromethanesulfonic anhydride (Tf₂O; 1.70 g, 6.0 mmol, 2.2 eq.) was added dropwise to a solution of triethyl phosphate (500 mg, 2.7 mmol, 1 eq.) in pyridine (8 ml) while stirring vigorously and cooling in an ice bath. This caused the solution to turn brown. The mixture was stirred for a further 16 h at 40 °C, during which time a colorless precipitate formed. The precipitate was filtered off, washed with pyridine, dried under vacuum, and identified by multinuclear NMR spectroscopy as Py₂PO₂[OTf] (Py = pyridiniumyl) (see Figures 1 and 2 ).

[0160] Yield: 840 mg (82%); 1< H NMR (CD 3 CN, 300 K, δ in ppm): 8.10 (m, 4H, Py- m -H), 8.62 (m, 2H, Py-pH), 9.28 (m, 4H, Py-oH); 19< F NMR (CD 3 CN, 300 K, δ in ppm): -79.3 (s, 3F, OTf -< ); 31< P NMR (CD 3 CN, , 300 K, δ in ppm): -15.9 (s, 1P).

[0161] The product of example 1 ( Figure 1 The phosphorus(V) ion shows a singlet in both the 31P and 19F NMR spectra. The resonance in the 31P NMR spectrum, with its chemical shift of δ(P) = -15.9 ppm, points to the phosphorus(V) precursor known from the literature (P. Rovnanik, L. Kapiĉka, J. Taraba, M. Ĉerník, ). Inorganic chemistry 2004, 43 , 2435). The resonance in the 19<F NMR spectrum, with its chemical shift of δ(F) = -79.3 ppm, points to the triflate anion known from the literature. The chemical shifts in the 1<H NMR spectrum at δ(H) = 8.10 ppm, δ(H) = 8.62 ppm, and δ(H) = 9.28 ppm indicate the presence of the pyridine ligand. Example 2: Synthesis of (LN ) 2 PO 2 [OTf] (LN = pyridiniumyl) from tributyl phosphate

[0162] Trifluoromethanesulfonic anhydride (Tf₂O; 2.33 g, 8.3 mmol, 2.2 eq.) was added dropwise to a solution of tributyl phosphate (1.0 g, 3.75 mmol, 1 eq.) in pyridine (8 ml) while stirring vigorously and cooling in an ice bath. This caused the solution to turn brown. The mixture was stirred for a further 16 h at 40 °C, during which time a colorless precipitate formed. The precipitate was filtered off, washed with pyridine, dried under vacuum, and identified by multinuclear NMR spectroscopy as Py₂PO₂[OTf] (Py = pyridiniumyl). The spectroscopic data are identical to those from Example 1.

[0163] Yield: 1.16 g (83%); 1< H NMR (CD 3 CN, 300 K, δ in ppm): 8.10 (m, 4H, Py-mH), 8.62 (m, 2H, Py-pH), 9.28 (m, 4H, Py-oH); 19< F NMR (CD 3 CN, 300 K, δ in ppm): -79.3 (s, 3F, OTf -< ); 31< P NMR (CD 3 CN, , 300 K, δ in ppm): -15.9 (s, 1P). Example 3: Synthesis of (LN ) 2 PO 2 [OTf] (LN = pyridiniumyl) from bis(2-ethylhexyl)phosphate (D2EHPA)

[0164] Trifluoromethanesulfonic anhydride (Tf₂O; 2.48 g, 8.8 mmol, 2.2 eq.) was added dropwise to a solution of bis(2-ethylhexyl)phosphate (1.29 g, 4.0 mmol, 1 eq.) in pyridine (8 ml) while stirring vigorously and cooling in an ice bath. This caused the solution to turn brown. The mixture was stirred for a further 16 h at 45 °C, during which time a colorless precipitate formed. The precipitate was filtered off, washed with pyridine, dried under vacuum, and identified by multinuclear NMR spectroscopy as Py₂PO₂[OTf] (Py = pyridiniumyl). The spectroscopic data are identical to those from Example 1.

[0165] Yield: 1.48 g (> 99 %); 1< H NMR (CD 3 CN, 300 K, δ in ppm): 8.10 (m, 4H, Py- m -H), 8.62 (m, 2H, Py-pH), 9.28 (m, 4H, Py-oH); 19< F NMR (CD 3 CN, 300 K, δ in ppm): -79.3 (s, 3F, OTf -< ); 31< P NMR (CD 3 CN, , 300 K, δ in ppm): -15.9 (s, 1P). Example 4: Reaction of trimethyl phosphate with p-toluenesulfonic anhydride in pyridine

[0166] Trimethyl phosphate (50 mg, 0.36 mmol) is dissolved in 2 ml of pyridine and it is p -Toluenesulfonic anhydride (256 mg, 0.78 mmol) was slowly added. The reaction mixture was stirred for 12 h at room temperature. A sample was taken and analyzed by multinuclear NMR spectroscopy. The formation of [(Py)₂PO₂]⁺ was detected in the 31< µP NMR spectrum (31< µP NMR (pyridine, C₆D₆ capillary, 300 K, δ in ppm): -15.3 (1P, s) (see Figure 3 ). Example 5: Reactions of (LN ) 2 PO 2 [OTf] with alcohols and alcoholates Example 5a): Reaction of (DMAP) 2 PO 2 [OTf] with MeOH

[0167] (DMAP)₂PO₂[OTf] (30 mg, 0.065 mmol) is dissolved in a mixture of CH₃CN and MeNO₂ (approx. 1 ml) and 2 drops of dry MeOH are added. The reaction mixture was stirred overnight and investigated by NMR spectroscopy. The 31<P NMR spectrum shows the selective formation of dimethyl phosphate [(MeO)₂PO₂-<] (31<P NMR (CH₃CN, MeNO₂, C₆D₆ capillary, 300 K, δ in ppm): -4.6 (1P, s). Example 5b): Reaction of (DMAP) 2 PO 2 [OTf] with PhOH

[0168] (DMAP)₂PO₂[OTf] (40 mg, 0.08 mmol) and phenol (17 mg, 0.17 mmol) are suspended in CH₃CN (approx. 1.5 ml) and stirred for 2 days at 40°C. The 31<pN NMR spectrum of the reaction solution shows the selective formation of diphenyl phosphate [(PhO)₂PO₂-] (31<pN NMR (CH₃CN, MeNO₂, C₆D₆ capillary, 300 K, δ in ppm): -11.5 (1p, s). Example 5c): Reaction of (Py) 2 PO 2 [OTf] with 2-ethylhexanol

[0169] (Py)₂PO₂[OTf] (500 mg, 1.35 mmol) is suspended in 2-ethylhexanol (5 mL) and stirred at 65°C for 3 days. The 31<p NMR spectrum of the reaction solution shows the selective formation of bis(2-ethylhexyl)phosphate [(RO)₂PO₂-2] (R = 2-ethylhexanoyl) (31<p NMR (neat, C₆D₆ capillary, 300 K, δ in ppm): 2.12 (1P, s)). The 2-ethylhexanol is removed under vacuum, and the residue is dissolved in n-hexane (6 mL) and degassed water (1 mL). After separation of the organic phase and subsequent drying under vacuum, bis(2-ethylhexyl)phosphate is obtained in 97% purity in 81% yield (347 mg). Example 5d): Reaction of (DMAP) 2 PO 2 [OTf] with KOtBu

[0170] To a cold (-30°C) suspension of (DMAP)₂PO₂[OTf] (50 mg, 0.11 mmol) in THF (1 ml), a solution of potassium tert-butanoate (25 mg, 0.22 mmol) in THF (1 ml) was slowly added, causing the suspension to turn slightly yellow. After 3 h, the 31<pN NMR spectrum of the reaction solution shows complete conversion to the corresponding di-tert-butylphosphate [(tBuO)₂PO₂-] (31<pN NMR (THF, C₆D₆ capillary, 300 K, δ in ppm): -5.9 (1p, s). Example 5e): Reaction of (Py) 2 PO 2 [OTf] with BINOL

[0171] (Py)₂PO₂[OTf] (200 mg, 0.54 mmol) and BINOL (155 mg, 0.54 mmol) are weighed together and suspended in pyridine (5 ml). The reaction mixture is then stirred at room temperature for 12 h. After 12 h, the 31<pN NMR spectrum of the reaction solution shows complete and clean conversion to the corresponding BINOL phosphate (31<pN NMR (pyridine, C₆D₆ capillary, 300 K, δ in ppm): 6.5 ppm (1p, s)). Aqueous work-up affords the pure product in 88% yield. Example 5f): Reaction of (Py) 2 PO 2 [OTf] with HOCH 2 CF 3

[0172] (Py)₂PO₂[OTf] (185 mg, 0.5 mmol) and 2,2,2-trifluoroethanol (110 mg, 1.1 mmol) are weighed together and suspended in pyridine (2.5 mL). The reaction mixture is stirred at room temperature for 12 h. After 12 h, the 31<pN NMR spectrum of the reaction solution shows complete and clean conversion to the corresponding bis(trifluoroethyl)phosphate [(CF₃CH₂O)₂PO₂-<pN] (31<pN NMR (THF, C₆D₆ capillary, 300 K, δ in ppm): -2.8 (1p, s). Aqueous work-up yields the pure product. Example 6: Reaction of (DMAP) 2 PO 2 [OTf] with PhMgBr

[0173] To a cold (-80°C) suspension of (DMAP)₂PO₂[OTf] (60 mg, 0.13 mmol) in CH₂Cl₂ (3 ml), 0.27 ml of a 1 M THF solution of phenylmagnesium bromide (0.27 mmol) is added. The reaction mixture is stirred overnight, resulting in a brown, clear solution. NMR analysis of the reaction solution shows the formation of diphenylphosphinate [(Ph)₂PO₂-< ] (31< P NMR (CD₃CN, 300 K, δ in ppm): 14.8 (1P, s). Example 7: Reactions of (LN ) 2 PO 2 [OTf] with amines Example 7a): Reaction of (Py) 2 PO 2 [OTf] with sodium triazolide

[0174] Solid (Py)₂PO₂[OTf] (150 mg, 0.40 mmol) is added to a suspension of sodium triazolide (74 mg, 0.81 mmol) in CH₃CN (2 ml), and the reaction mixture is stirred for a further 2 h. The colorless suspension is filtered, and the solid is washed with CH₃CN and then dried under vacuum. The solid is analyzed by multinuclear NMR spectroscopy, confirming the formation of the corresponding (triazole)₂PO₂. The 31<P NMR spectrum shows two different isomers (31<P NMR (DMSO-d₆, 300 K, δ in ppm): -22.3 (1P, s; 85%), -24.4 (1P, s; 15%). Example 7b): Reaction of (Py) 2 PO 2 [OTf] with sodium imidazolide

[0175] Solid (Py)₂PO₂[OTf] (100 mg, 0.27 mmol) is added to a suspension of sodium imidazolide (54 mg, 0.54 mmol) in CH₃CN (2 ml), and the reaction mixture is stirred for a further 2 h. The colorless suspension is filtered, and the solid is washed with CH₃CN and then dried under vacuum. The solid is analyzed by multinuclear NMR spectroscopy, which confirms the formation of the corresponding (imidazole)₂PO₂. The 31<P NMR spectrum shows two different isomers (31<P NMR (DMSO-d₆, 300 K, δ in ppm): -20.8 (1P, s; 11%), -21.4 (1P, s; 89%). Example 7c): Reaction of (Py) 2 PO 2 [OTf] with sodium pyrazolide

[0176] Solid (Py)₂PO₂[OTf] (100 mg, 0.27 mmol) is added to a suspension of sodium pyrazolide (49 mg, 0.54 mmol) in CH₃CN (2 ml), and the reaction mixture is stirred for a further 12 h. The colorless suspension is filtered, and the solid is washed with CH₃CN and then dried under vacuum. The solid is examined by multinuclear NMR spectroscopy, which confirms the formation of the corresponding (pyrazole)₂PO₂. (31< P NMR (DMSO-d 6 , 300 K, δ in ppm): -18.2 (1P, s). Example 7d): Reaction of (Py) 2 PO 2 [OTf] with NH 3

[0177] (Py)₂PO₂[OTf] (100 mg, 0.27 mmol) is dissolved in CH₃CN (2 ml) and NH₃ 0.54 ml (0.5 M in dioxane) is added. The reaction mixture is stirred for a further 12 h. The colorless suspension is filtered and the solid is washed with CH₃CN and then dried under vacuum. The solid is examined by multinuclear NMR spectroscopy and shows the formation of, among other things, (NH₂)₂PO₂. (31<P NMR (DMSO-d₆, 300 K, δ in ppm): -0.3 (1P, pent. 2< J PH = 8 Hz). Example 7e): Reaction of (Py) 2 PO 2 [OTf] with quinuclidine

[0178] (Py)₂PO₂[OTf] (50 mg, 0.13 mmol) is suspended in THF (2 ml) and solid quinuclidine (40 mg, 0.35 mmol) is added. The reaction mixture is stirred for a further 12 h. The colorless suspension is filtered and the solid is then dried under vacuum. The solid is examined by multinuclear NMR spectroscopy and shows the formation of the mixed-substituted derivative (Quin)(Py)PO₂. (31< µP NMR (CD₃CN, 300 K, δ in ppm): -3.3 (1P, s). List of illustrations

[0179] Figure 1 : 1< H NMR spectrum of Py 2 PO 2 [OTf] recycled from triethyl phosphate (CD 3 CN, 300 K). Figure 2 : 31< P NMR spectrum of Py 2 PO 2 [OTf] recycled from triethyl phosphate (CD 3 CN, 300 K). Figure 3 : 31< P NMR spectrum of the reaction OP(OMe) 3 with 2.2 Ts 2 O (p-toluenesulfonic anhydride) in pyridine (300 K, C 6 D 6 capillary).

Claims

1. A process for the synthesis of nitrogen-containing phosphorus(V) precursors of formula (I), wherein the method comprises the following steps in the order indicated: a) providing a phosphoric acid ester; b) reacting the phosphoric acid ester from step a) with an oxygen acceptor in the presence of a Lewis base LN capable of coordination via a nitrogen atom, wherein the oxygen acceptor is the cation of a sulfonic acid anhydride according to formula (II) and the sulfonic acid anhydride is according to formula (III), wherein, according to step b), alternatively either b1) the phosphoric acid ester from step a) is reacted with a sulfonic acid anhydride according to formula (III) in the presence of a Lewis base LN, or b2) the phosphoric acid ester from step a) is reacted with the reaction product of a sulfonic acid anhydride according to formula (III) with a Lewis base LN, wherein said reaction product is according to formula (IV) wherein R is an aliphatic or aromatic hydrocarbon radical which may contain heteroatoms, the number of carbon atoms of the radical R being from 1 to 21, and the heteroatoms being selected from the group consisting of oxygen, nitrogen, fluorine, chlorine, bromine, iodine, and mixtures thereof, wherein the Lewis base LN capable of coordination via a nitrogen atom is a nitrogen containing heteroaromatic compound containing a six-membered heteroaromatic ring containing a nitrogen atom capable of coordination, wherein the number of carbon atoms of the Lewis base LN is from 4 to 19, and wherein the phosphoric acid ester from step a) is according to one of the formulae (Va), (Vb), and (Vc) wherein RAlk is a hydrocarbon radical which may contain heteroatoms.

2. The process according to claim 1, wherein the reaction of the phosphoric acid ester with an oxygen acceptor in step b) is carried out in the presence of at least five equivalents of a Lewis base LN.

3. The process according to claim 1 or 2, wherein the number of carbon atoms of each RAlk is from 1 to 50 and wherein the number of carbon atoms of all RAlk together in one of the formulae (Va), (Vb), or (Vc) is from 1 to 50, and wherein the heteroatoms of RAlk are selected from the group consisting of nitrogen, oxygen, sulphur, fluorine, chlorine, and bromine.

4. The process according to any one of claims 1 to 3, wherein a carbon atom of any hydrocarbon residue RAlk in any one of the formulae (Va), (Vb), or (Vc) that is directly bonded to the oxygen atom of the ester bond of the phosphoric acid ester is bonded to three further atoms.

5. The process according to any one of claims 1 to 4, wherein R is an aliphatic hydrocarbon residue having 1 to 6 carbon atoms, which contains 0 to 3 heteroatoms selected from the group consisting of oxygen, nitrogen and fluorine.

6. The process according to any one of claims 1 to 4, wherein R is an aromatic hydrocarbon residue defined by the following formula (Illa) wherein the radicals R1, R2, R3, R4, and R5 are selected from the following combinations: R1, R2, R3, R4, R5 = H, R1, R2, R3, R4, R5 = CH3, R1, R2, R3, R4 = H and R5 = CH3, R1, R2, R3, R4 = H and R5 = F, R1, R2, R3, R4 = H and R5 = Cl, R1, R2, R3, R4 = H and R5 = OCH3, R1, R2, R3, R4 = H and R5= NO2, R1, R2, R3, R4 = H and R5 = CF3, R1, R2, R4 = H and R3, R5 = CH3, R2, R4 = H and R1, R3, R5 = CH3, R2, R3, R5 = H and R1, R4 = CH3, or R1, R2, R4, R5 = H and R3 = CH3.

7. The process according to claims 5 and 6, wherein R is trifluoromethyl or R is defined as in formula (Illa), and the following applies: R1, R2, R4, R5 = H and R3 = CH3.

8. The process according to any one of claims 1 to 7, wherein the Lewis base LN contains one or two six-membered heteroaromatic rings, the Lewis base LN contains one or two coordination-capable nitrogen atoms per six-membered heteroaromatic ring in the six-membered heteroaromatic ring, wherein the Lewis base LN contains a total of one or two nitrogen atoms.

9. The process according to any one of claims 1 to 8, wherein the Lewis base LN independently contains one or two nitrogen atoms, contains zero, one or two oxygen atoms, contains zero, one, two, three or four heteroatoms selected from the group consisting of fluorine, chlorine, bromine and iodine, and contains no further heteroatoms.

10. The process according to any one of claims 1 to 9, wherein the Lewis base LN is selected from the group consisting of pyridines, picolines, lutidines, collidines, bipyridines, pyridazines, pyrimidines, pyrazines, quinolines and isoquinolines.

11. The process according to any one of claims 1 to 10, wherein the Lewis base LN is selected from the group consisting of pyridine, 4-dimethylaminopyridine, and mixtures thereof.

12. The process according to any one of claims 1 to 11, wherein the synthesis is carried out in an aprotic solvent.

13. The process according to claim 12, wherein the solvent is pyridine.