Process for preparing acylphosphanes and their oxides and sulphides

1. A process for the preparation of bis-acylphosphanes of formula I

R 1 P(COR 2 ) 2

wherein

R 1 is unsubstituted phenyl or phenyl substituted by one to five halogen, C 1 -C 8 -alkyl, C 1 -C 8 -alkylthio and/or C 1 -C 8 -alkoxy;

R 2 is C 1 -C 18 -alkyl or C 2 -C 18 -alkenyl; C 1 -C 18 -alkyl or C 2 -C 18 -alkenyl substituted once or more than once by halogens, —OR 10 , —OCO—R 10 , —OCO-Hal, —COO—R 10 , —N(R 11 )—CO—R 10 , —N(R 11 )—CO-Hal, —CO—NR 11 R 10 , —CH═CH—CO—OR 10 or —CH═CH-phenyl; —C(C 1 -C 4 -alkyl)=C(C 1 -C 4 -alkyl)-CO—OR 10 or —C(C 1 -C 4 -alkyl)=C(C 1 -C 4 -alkyl)-phenyl;

C 5 -C 12 -cycloalkyl, C 2 -C 18 -alkenyl, phenyl-C 1 -C 4 -alkyl, phenyl, naphthyl, biphenyl or a 5- or 6-membered —O—, S— or N-containing heterocyclic ring, the radicals phenyl, naphthyl, biphenyl or the 5- or 6-membered —O—, S— or N-containing heterocyclic ring being unsubstituted or substituted by one to five halogen, C 1 -C 8 -alkyl, C 1 -C 8 -alkoxy and/or C 1 -C 8 -alkylthio;

R 10 is hydrogen, C 1 -C 18 -alkyl, or C 2 -C 18 -alkyl which is interrupted by one or more non-successive —O-atoms, C 5 -C 12 -cycloalkyl, phenyl-C 1 -C 4 -alkyl, C 2 -C 18 -alkenyl, phenyl, naphthyl or biphenyl being unsubstituted or substituted by one to five C 1 -C 8 -alkyl, C 1 -C 8 -alkoxy, C 1 -C 8 -alkylthio and/or halogen;

R 11 is hydrogen, C 1 -C 18 -alkyl, C 2 -C 18 -alkyl which is interrupted by one or more non-successive O atoms, C 5 -C 12 -cycloalkyl, C 2 -C 18 -alkenyl, phenyl-C 1 -C 4 -alkyl, phenyl, naphthyl, pyridyl, the radicals phenyl, naphthyl or pyridyl being unsubstituted or substituted by one to five C 1 -C 8 -alkyl, C 1 -C 8 -alkoxy, C 1 -C 8 -alkylthio and/or halogen;

which process comprises

a) selective reduction by hydrogenation of dichlorophenylphosphanes of the formula II

R 1 P(Cl) 2

by means of hydrogen at a temperature in the range from 20 to 200° C. and under hydrogen pressure of atmospheric pressure to 20 bar in the presence of a hydrogenation catalyst, a tertiary aliphatic amine or an aromatic amine and in the presence of a non-protic solvent which is unreactive under the hydrogenation conditions to obtain cyclic phenylphosphanes (R 1 P) n (n=4 to 6); or

b) selective reduction by hydrogenation of R 1 P(Cl) 2 by means of hydrogen at a temperature in the range from 80 to 250° C. and under hydrogen pressure of 25 to 250 bar in the presence of a hydrogenation catalyst, a tertiary aliphatic amine or an aromatic amine and in the presence of a non-protic solvent which is unreactive under the hydrogenation conditions to obtain R 1 PH 2 ;

c) subsequent reaction with an acid halide of formula III in the presence of an appropriate base R 2 COHal

wherein R 2 is as defined above.

2. A process according to claim 1 , wherein R 1 is unsubstituted phenyl and R 2 is phenyl which is substituted in 2,6- or 2,4,6-position by C 1 -C 4 -alkyl and/or C 1 -C 4 -alkoxy.

3. A process according to claim 2 , wherein R 2 is 2,4,6-trimethylphenyl.

4. A process according to claim 1 , comprising the steps a) and c).

5. A process according to claim 1 , comprising the steps b) and c).

6. A process according to claim 1 , wherein the tertiary amine is pyridine or triethylamine.

7. A process according to claim 1 , wherein the non-protic solvent which is unreactive under hydrogenation reactions is selected from an aromatic hydrocarbon, an aliphatic hydrocarbon, an ether, an ester, N—C 1 -C 6 -alkylimidazoles, N—C 1 -C 6 -alkyl-1,2,4-triazoles and mixtures thereof.

8. A process according to claim 7 , wherein the non-protic solvent which is unreactive under hydrogenation reactions is toluene or xylene.

9. A process according to claim 1 , wherein the catalyst is selected from palladium on carbon and palladium on alumina.

10. A process according to claim 2 , comprising the steps a) and c).

11. A process according to claim 2 , comprising the steps b) and c).

12. A process according to claim 2 , wherein the tertiary amine is pyridine or triethylamine.

13. A process according to claim 2 , wherein the non-protic solvent which is unreactive under hydrogenation reactions is selected from an aromatic hydrocarbon, an aliphatic hydrocarbon, an ether, an ester, N—C 1 -C 6 -alkylimidazoles, N—C 1 -C 6 -alkyl-1,2,4-triazoles and mixtures thereof.

14. A process according to claim 12 , wherein the non-protic solvent which is unreactive under hydrogenation reactions is selected from an aromatic hydrocarbon, an aliphatic hydrocarbon, an ether, an ester, N—C 1 -C 6 -alkylimidazoles, N—C 1 -C 6 -alkyl-1,2,4-triazoles and mixtures thereof.

15. A process according to claim 2 , wherein the catalyst is selected from palladium on carbon and palladium on alumina.

16. A process according to claim 12 , wherein the catalyst is selected from palladium on carbon and palladium on alumina.

17. A process according to claim 14 , wherein the catalyst is selected from palladium on carbon and palladium on alumina.

18. A process according to claim 1 wherein the hydrogenation catalyst comprises a metal, metal oxide or Raney form of metal wherein the metal is selected from ruthenium, rhenium, rhodium, platinum, palladium, copper, nickel, cobalt and molybdenum or the hydrogenation catalyst is copper chromite.

19. A process according to claim 18 wherein the catalyst is supported on carbon, niobium, titania, zirconia, silica, tin, alumina or mixtures thereof.