CA2286824A1

CA2286824A1 - Method for producing vinyl phosphonic acid compounds

Info

Publication number: CA2286824A1
Application number: CA002286824A
Authority: CA
Inventors: Jochem Henkelmann; Thomas Preiss; Arnd Bottcher
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1997-04-15
Filing date: 1998-04-08
Publication date: 1998-10-22
Also published as: JP2001518905A; CN1100783C; EP0975643B1; JP4280307B2; ES2180171T3; EP0975643A1; DE19715667A1; CN1255138A; DE59804673D1; WO1998046613A1

Abstract

The invention relates to a method for producing vinyl phosphonic acid compounds of general formula (I) wherein R1 and R2 are independently H, C1-16-aryl, C7-12-alkaryl or C7-12-aralkyl radicals, wherein the organic radicals can be substituted by one or several halogen atoms, hydroxyl, acyl or acetoxy groups. Production occurs by reacting phosphoric acid compounds of general formula (II) with acetylene in the presence of a Pd(II) complex and/or a Pd(0) complex or corresponding Pt complexes as a catalyst.

Description

r METHOD FOR PRODUCING VINYL PHOSPHONIC ACID COMPOUNDS
to The present invention relates to a process for preparing vinylphosphonic acid compounds using certain catalysts, and to the use of such catalysts is for the preparation process.
Vinylphosphonic acid compounds, in particular dialkyl vinylphosphonates, have importance as precursors for preparing vinylphosphonic acid and as monomers for copolymerization for producing adhesives or flame-resistant zo plastics.
Various processes for preparing them are known. In the process described in DE-C-21 32 962, ethylene oxide is reacted with phosphorus trichloride to give 2-chloroethanephosphonic dichloride, and this compound is con-es verted into bis-2-chloroethyl 2-chloroethanephosphonate. The resulting compound is then reacted with phosgene in the presence of a catalyst.
Amines, heterocyclic nitrogen compounds, as well as tertiary phosphines, are used as catalyst.
so DE-A-30 O1 894 describes a process for preparing vinylphosphonic acid derivatives, in which dialkyl 2-acetoxyethanephosphonates are cleaved in the presence of acidic or basic catalysts. The basic catalysts proposed are tertiary amines and phosphines, as well as ammonium salts or phosphonium salts, besides heterocyclic compounds and amides. The disadvantage of the process is the formation of a mixture of vinylphosphonic acid derivatives. The maximum content of dialkyl s vinylphosphonates is 23 % .
An improved variant of this process disclosed in DE-A-31 20 437 entails a distillation followed by reaction of the bottom product mixture resulting from the distillation with orthocarboxylates to give dialkyl vinylphos-io phonates.
EP-A-0 722 948 discloses thermal cleavage of dimethyl 2-acetoxyethanephosphonate in the gas phase to give acetic acid and dimethyl vinylphosphonate. No catalyst is used in this case.
is The disadvantages of the above processes are the formation of product mixtures, elaborate, multistage synthetic processes, the need to use high reaction temperatures, and the use of chlorinated starting compounds. The large proportion of byproducts in particular considerably impairs the 2o economics of the process.
A simple addition reaction is advantageous for synthesizing vinylphosphonic acid compounds and results in the required product in high yields. One example of a reaction of this type is addition of dialkyl is phosphites onto acetylene. US 3,673,285 describes the addition of alkynes onto diethyl phosphite at from 130 to 200°C in the presence of nickel-phosphine complexes. On addition of acetylene, the corresponding diethyl vinylphosphonate is obtained in a yield of 30 % . The disadvantage of this process is, besides the low yield, the tendency of the phosphorous esters 3o to decompose in a strongly exothermic reaction at temperatures as low as 130°C.
It is an object of the present invention to provide a process for preparing vinylphosphonic acid compounds which avoids the disadvantages of known s processes and makes the required products available with high selectivity and yield under mild conditions from acetylene and phosphorous acid compounds.
~Ve have found that this object is achieved by a process for preparing io vinylphosphonic acid compounds of the formula (I) where R1 and R2 are, independently, H, C~_16-alkYl, C6-12-aryl, C~_12' alkaryl or C~_12-aralkyl, it being possible for the organic radicals to be zo substituted by one or more halogen atoms, hydroxyl, acyl or acetoxy groups, by reacting phosphorous acid compounds of the formula (II) RZ /
-O
where R1 and R2 have the above meaning, with acetylene in the presence of a Pd(II) complex and/or of a Pd(0) complex or corresponding Pt so complexes as catalyst.

We have found that the reaction of acetylene with phosphorous acid compounds, in particular dialkyl phosphites, to give vinylphosphonic acid compounds, in particular dialkyl vinylphosphonates, is possible with high selectivity and yield by using a catalytic amount of a palladium or s platinum complex, preferably palladium complex, especially in homogeneous phase. Similar palladium complexes have been used for hydrophosphorylation of terminal higher alkynes such as 1-octyne, see J.
Am. Chem. Soc., 118 (1996) 1571 - 1572. However, reaction with io acetylene is not mentioned or proposed.
~~e have found that acetylene can be reacted under very mild conditions with very high selectivity using a palladium catalyst to give vinylphosphonic acid compounds, in particular dialkyl vinylphosphonates, directly without any dimerization, oligomerization or polymerization of i5 acetylene or double reaction to give a tetraalkyl ethylenediphosphonate.
In the phosphorous acid compounds of the formula (II) employed for the reaction, Rl and R'- are, independently, H, C1_16-alkyl, C6_1~-aryl, C~_1.,-alkaryl or C~_12-aralkyl, it being possible for the organic radicals to be 2o substituted by one or more halogen atoms, hydroxyl, acyl or acetoxy groups. Rl and R'- are preferably, independently, linear C1_t2-alkyl, phenyl, (Ci_6-alkyl)phenyl or phenyl(C1_6-alkyl). Rl and R2 are particularly preferably, independently, linear C1_6-alkyl radicals. These radicals are zs preferably unsubstituted.
If Rl and R' differ from hydrogen, then the compounds employed are diesters of phosphorous acid. Reaction thereof results in diesters of vinylphosphonic acid of formula (I). This reaction can be followed by cleavage of the ester groups, resulting in vinylphosphonic acid, R10H and 3o RZOH.

Conversion of the phosphorous acid compounds into the vinylphosphonic acid compounds takes place in the presence of a Pd(I~ complex and/or of a Pd(0) complex or corresponding Pt complex, but preferably Pd complex as catalyst.
The catalyst is usually present in homogeneous phase for this purpose.
The Pd(0) complex employed preferably has phosphine ligands or phosphate ligands.
A large number of ligands are suitable as phosphine ligands or phosphate ligands.
For example, the ligands may have the formula PXYZ where X, Y and Z are, independently, alkyl, aryl, allcoxy or aryloxy radicals having up to 18 carbon atoms.
to Alkyl or aryl radicals are preferred in this connection, especially aryl radicals.
Corresponding ligands are described, for example, in DE-A-1 593 277. They are preferably triarylphosphines or triaryl phosphates in which the aryl groups are unsubstituted or substituted. Suitable substituents are C~.~-alkyl, acyl or acetoxy radicals. The triarylphosphine is preferably unsubstituted. Triphenylphosphine is t5 particularly employed as phosphine ligand. The catalyst used particularly preferably according to the invention is tetrakis(triphenylphosphine)palladium(0).
The complexes may be composed, for example, of monodentate or bidentate ligands.
Examples of suitable complex structures are the following:
\ / R' /P~ iX ~p~ ,P\ jp~ ~P
R\ P M\Y R\ M\ iR R\ M\
P P P X
R R' R R ' R' R ' R R' where the meanings are 2o M Pd, Pt, preferably Pd R independently at each posirion organic radicals linked via O and/or C atoms to the phosphorus atoms, in particular aryl radicals or aryloxy a radicals having 2 sites capable of linkage, R,R" independently at each position monovalent organic radicals, in particular aryl andlor aryloxy radicals X, Y independently monovalent anionic ligands.
The charges therein are equalized, if necessary employing canons or anions without coordinate links to equalize the charges.
io It is preferred for the monovalent radicals to be derived from benzene or phenol and for the divalent radicals to be derived from biphenyl, 1,1'-binaphthyl, biphenyloxy and/or 1,1'-binaphthyloxy radicals. It is moreover possible for all the aromatic radicals to be substituted, for example by is one or more C1-6-alkyl radicals or corresponding alkoxy radicals. The biphenyl and binaphthyl radicals, and radicals derived therefrom, are linked to the phosphorus atom via 2 positions in the molecule. It is possible for both positions to be linked to the same phosphorus atom. It is also possible for them to be linked to different phosphorus atoms and 2o thus produce bridged structures which have, for example, 2 phosphorus atoms and 3 of said radicals. Suitable corresponding bidentate phosphate ligands are described in US 5',512,695. The phosphate ligands described therein can also be employed in analogous form as phosphine ligands.
Further suitable monodentate and bidentate aromatic ligands are described 2s in WO 95/29153. The described ligands can in this case likewise be employed as phosphine or phosphate ligands.
Pd(II) complexes which can be used according to the invention preferably have the phosphine ligands, phosphate ligands, aryl cyanides or alkyl 3o cyanides described for Pd(0) complexes as ligands. The aryl cyanides can moreover be substituted as above. Benzonitrile or acetonitrile are preferably employed. Particularly preferred Pd(II) complexes are Pd(C6HSCN)2C12, Pd(CH3CN)4(BF4)2 or Pd((C6H~)3P)2C12.
s The catalysts can moreover be formed in situ in the reaction.
The catalysts employed according to the invention are normally employed in an amount of from 0.01 to 10% by weight, preferably in an amount of from 0.5 to 3 % by weight, particularly preferably 1 to 2 % by weight, io based on the amount of phosphorous acid compounds to be vinylated, in particular dialkyl phosphites.
The temperature in the reaction is, as a rule, from 20 to 120°C, preferably 20 to 80°C, particularly preferably 60 to 80°C.
is The reaction can moreover be carried out without solvent or in the presence of an inert solvent. Examples of inert solvents which can be used are cyclic ethers such as THF, long-chain ethers such as triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether.
The reaction is carried out under atmospheric pressure or elevated pressure, preferably at from 1 to 20, particularly preferably 1.5 to 6, bar (absolute). This preferably entails mixing the phosphorous acid compound of the formula (II) and the catalyst, and passing in acetylene. Once the 2s reaction is complete, the product can be removed by distillation.
The novel process can be carried out continuously or batchwise.
The invention also relates to the use of the catalysts described above in 3o the preparation of vinylphosphonic acid compounds, in particular _g_ vinylphosphonic esters, specifically dialkyl vinylphosphonates.
The invention is explained in detail by means of Examples shown hereafter.

6 g of dimethyl phosphite were stirred with 20 ml of tetrahydrofuran in a 4-neck flask which had a capacity of 500 ml and was equipped with an io internal thermometer, dry-ice condenser and gas introduction tube, and were degassed under argon. After addition of 2 mol % tetrakis- (tri-phenylphosphine)palladium(0), 6 l/h acetylene were passed into the reaction solution at 60°C for 24 h. Dimethyl vinylphosphonate was isolated in 90'~o yield after workup by distillation.
is 2~ g of diethyl phosphite were degassed under argon while stirring in a 4-neck flask which had a capacity of 500 ml and was equipped with an zo internal thermometer, dry-ice condenser and gas introduction tube. After addition of 1 mol % tetrakis(triphenylphosphine)palladium(0), 6 l/h acetylene were passed into the reaction solution at 60°C for 24 h.
Diethyl vinylphosphonate was isolated in 95 % yield after workup by distillation.
EXA,~iPLE 3 65 g of dimethyl phosphite were stirred with 110 ml of tetrahydrofuran in an autoclave with a capacity of 300 ml. After addition of 0.7 mol %
so tetrakis(triphenylphosphine)palladium(0), initially 5 bar of nitrogen and bar of acetylene were injected. After heating the autoclave to 65°C, further acetylene was injected to 20 bar. The amount of acetylene taken up at this temperature was replaced each hour for 20 h and then, after cooling, the reaction discharge was flushed with nitrogen and distilled.
s Dimethyl vinylphosphonate was isolated in 95 % yield.

Claims

We claim:

1. A process for preparing vinylphosphonic acid compounds of the formula (1) where R1 and R2 are, independently, H, C1-16-alkyl, C6-12-aryl, C7-12-alkaryl or C7-12-aralkyl, it being possible for the organic radicals to be substituted by one or more halogen atoms, hydroxyl, acyl or acetoxy groups, by reacting phosphorous acid compounds of the formula (II) where R1 and R2 have the above meaning, with acetylene in the presence of a Pd(H) complex and/or of a Pd(0) complex or corresponding Pt complexes as catalyst at a temperature of from 20 to 80°C.

2. A process as claimed in claim 1, wherein R1 and R2 are, independently, linear C1-16-alkyl radicals.

3. A process as claimed in claim 2, wherein the ester groups are cleaved after the reaction, resulting in vinylphosphonic acid, R1OH and R2OH.

4. A process as claimed in any of claims 1 to 3, wherein a Pd(0) complex which has triarylphosphine ligands or triarylphosphite ligands is employed as catalyst.

5. A process as claimed in claim 4, wherein the complex is tetrakis(triphenylphosphine)palladium(0).

6. A process as claimed in any of claims 1 to 3, wherein a Pd(II) complex which has as ligands triarylphosphines, triaryl phosphites, aryl cyanides and/or alkyl cyanides is employed as catalyst.

7. A process as claimed in claim 5, wherein Pd(C6H5CN)2Cl2, Pd(CH3CN)4(BF4)2 and/or Pd((C6H5)3P)3Cl2 are employed as catalyst.

8. A process as claimed in any of claims 1 to 7, which has one or more of the following features:
- presence of an inert solvent - pressure from 1 to 20 bar - temperature from 20 to 120°C
- amount of catalyst employed from 0.01 to 10% of the weight of the phosphorous acid compounds employed - process carried out continuously.