GB2185740A

GB2185740A - Process for the preparation of ketones

Info

Publication number: GB2185740A
Application number: GB08601913A
Authority: GB
Inventors: Eit Drent
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1986-01-27
Filing date: 1986-01-27
Publication date: 1987-07-29
Also published as: GB8601913D0

Abstract

Process for the preparation of a mixture comprising alkenically unsaturated monoketones and dialkyl monoketones, all monoketones having the same number of carbon atoms in the groups bound to the carbonyl group, by reacting carbon monoxide with an alkene having at least three carbon atoms and having the same number of carbon atoms as each of the groups bound to the carbonyl group in the presence of a catalytic system prepared by combining:- a) Pd and/or a Pd compound, b) an acid having a pKa<2, except hydrohalogenic and carboxylic acids, and c) a bidentate ligand R<1>R<2>-M-R-M-R<3>R<4> in which M is P, As or Sb, R is a divalent organic bridging group having at least 2 C atoms in the bridge, and R<1-4> are optionally substituted hydrocarbon groups, followed by isolation of said monoketones from the reaction mixture.

Description

SPECIFICATION Process for the preparation of ketones The invention relates to a process for the preparation of a mixture comprising alkenically unsaturated monoketones and dialkylmonoketones, all monoketones having the same number of carbon atoms in the groups bound to the carbonyl group.

Alkenically unsaturated monoketones are of interest as intermediates in the preparation of perfumes, vitamins, dyes and plastics and in steroid chemistry (see European Patent Application 0,017,284, British Patent Application 2,028,321, British Patent Specification 1,340,611 and German Auslegeschrift 2,150,992).

Dialkylmonoketones may be used, for example, as solvents.

According to European Patent Application 0,017,284alkenically unsaturated monoketones can be prepared by a three-step process starting from a diketone.

It is an object of the present invention to prepare said mixture of monoketones starting from simple compounds and in one step only.

Accordingly, the invention provides a process forthe preparation of a mixture comprising alkenically unsaturated monoketones and dialkylmonoketones, all monoketones having the same number ofcarbon atoms in the groups bound to the carbonyl group which process comprises reacting carbon monoxide with an alkene having at least three carbon atoms per molecule and having the same numberof carbon atoms as each of the groups bound to said carbonyl group in the presence of a catalytic system prepared bycombin ing::- (a) palladium and/or a palladium compound, (b) an acid having a pKa of less than 2, provided it is neither a hydrohalogenic acid nor carboxylic acid and (c) a bidentate ligand of the formula I 1 R2-M-R-M-R3R4 (I) in which M represents a phosphorus, arsenic or antimony atom, R represents a divalent organic bridging group having at leasttwo carbon atoms in the bridge, none of these carbon atoms carrying substituentsthat may cuase steric hindrance and in which R1, R2, R3 and R4 represent identical or different optionallysubstituted hydrocarbon groups, followed by isolation of said monoketones from the reaction mixture thus obtained.

It is known from European patent application 121965 to apply the catalytic system described hereinbefore in a process for the preparation of polyketones by polymerizing a mixture of carbon monoxide and an alken ically unsaturated hydrocarbon. Ethylene is most preferred in this known process and, as shown in the examples of said patent application, selectively gives polyketones. It is therefore very surprising that in the absence of ethylene application of alkenes having at least three carbon atoms per molecule gives rise to formation of a major amount of a mixture comprising said alkenically unsaturated monoketones and dia lkylmonoketones, and a minoramountofpolyketones.

The anions of the acids having a pKa of less than 2 are preferably non-coordinating, by which is meantthat little or no covalent interaction takes place between the palladium and the anion (cf. GB-A 2,058,074). Typical examples of such anions are PF6, SbF6-, BF4- and C104-.

Preferred acids are sulphonic acids and acids that can be formed, possibly in situ, by interacting a Lewis acid such as, for example BF3, AsF5, SbF5, PF5, TaF5 or NbF5 with a Broensted acid such as, for example, a hydrohalogenic acid, in particular HF,fluorosulphonic acid, phosphoric acid orsulphuricacid. Specific examples of acids of the lattertype are H2SiF6, HBF4, HPF6 and HSbF6. Examples of usable sulphonic acids arefluorosulphonic acid and chlorosulphonic acid and the hereinafter specified sulphonic acids.

A preferred group of acids has the general formula II

in which X represents a sulphur or a chlorine atom and, if X represents a chlorine atom, R5 represents an oxygen atom and, if X represents a sulphur atom, R5 represents an OH group or an optionallysubstituted hydrocarbon group.

When the herein before stated acids are used in the process according to the invention, the anions ofthe acids can be considered to be non-coordinating.

In the acids having the general formula 11, the optionally substituted hydrocarbon group represented by R5 is preferably an alkyl, aryl, araikyl oralkaryl group having 1-30, in particular 1-14,carbon atoms. The hydrocarbon group may, for example, be substituted with the halogen atoms, in particularfluorine atoms. Examples of suitable acids ofthe general formula II are perchloric acid, suiphuric acid, 2-hydroxypropane-2 sulphonic acid, p-toluenesulphonic acid and trifluoromethanesulphonic acid, the lasttwo acids being the most preferred. The acid of the general formula II can also be an ion exchanger containing sulphonic acid groups, such as, for example, Amberlite 252 H ("Amberlite" is a trade name).In that case, the hydrocarbon group R5 is a polymeric hydrocarbon group substituted with sulphonic acid groups, for example a polystyrene group.

The acid having a pKa of less than 2 is preferably present in the reaction mixture in a quantity in the range of from 0.01 to 150, in particular 0.1 to 100 and most preferably 1 to 50 equivalents per gram atom of palladium.

The aforesaid pKa is measured in aqueous solution at 18"C.

The alkene having at leastthree carbon atoms per molecule may be straight or branched and the carbon atoms of the carbon-carbon double bond may be secondary or tertiary and one of the carbon atoms ofthe double bond may be primary. Alkenes having less than 30 and, in particular, less than 10 carbon atoms per molecule are preferred. Examples of suitable alkenes are propene, 1 -butene, 2-butene, 1 -pentene, 2-pentene, 3-methyl-1 -butene and 1 -hexene. Very good results have been obtained with propene.

The quantity of palladium compound is not critical. Preferably, quantities between 1 or8 and 10-1 mol palladium compound per mol alkene are used. The molar ratio of alkene to carbon monoxide will as a rule be in the range of from 5:95 to 95:5, preferably from 1:5 to 5:1.The molar ratio of carbon monoxideto hydrogen is preferably in the range of from 0.9 to 10.

Both homogeneous and heterogeneous palladium compounds can be used. Homogeneous systems are preferred. Suitable palladium compounds are salts of palladium with, for example nitric acid sulphuric acid or alkanoic acids having not more than 12 carbon atoms per molecule. Salts of hydrohalogenic acids are theoreticaliy also usable, but have the drawback that the halogen ion may have a corrosive action. Palladium carboxylates are the catalyst compounds preferably used, more preferablythose having less than 12 carbon atoms per molecule, in particular palladium acetate. Palladium acetylacetonate is another example of a palladium compound that can be used. Palladium on carbon and palladium bonded to an ion exchanger, for example one containing sulphonic acid groups, are examples of suitable heterogeneous palladium com pounds.

Where, in the bidentate ligand, it is said that substituents offering steric hindrance should be absent, this meansthat no substituents may be presentthat are ableto hindertheformation of complexcompounds having the general formula Ill

In that formula, Y represents a non-coordinating anion, whilst Pd2+ can also be written as

in which the ligands L1 and L2 are weakly coordinated solvent ligands, e.g. acetonitrile, methanol, acetone, or acetylacetone, or correspond with those employed in the palladium compounds described in the preceding paragraph.

In the bidentate ligand, M preferably represents a phosphorus atom. Hydrocarbon groups R1, R2, R3 and R4 will as a rule contain 2to 18 carbon atoms, preferably 6 to 14 atoms. Aryl groups arethe mostsuitable,in particularthe phenyl group. Preferred bridging groups -R- are those having the formula CR6R7n in which R6 and R7 are hydrogen atoms or optionally substituted hydrocarbon groups offering no steric hindrance and n is an integer of at leasttwo, preferably not more than 5, and most preferably 2,3 or4.

Substituents R6 and R7 are preferably hydrogen atoms. The bridging groups R may also make part of a cyclic structure, e.g. an aromatic or cycloaliphatic group, the carbon to carbon bond or bonds in the bridge may be saturated or unsaturated and in the bridge or in the cyclic or non-cyclic groups attached to the bridge one of more hetero atoms, e.g. sulphur, oxygen, iron or nitrogen, may have been substitutedforcarbon atoms, other than the two carbon atoms which must be present in the bridge linking both atoms M.

Examples of the suitable bidentate ligands are 1,3-di(diphenylphosphino)propane, 1,4-di(diphenylphosphino)butane, 2,3-dimethyl-1 ,4-di(diphenylphosphino)butane, 1,5-di(methylphenylphosphino)pentane, 1,4-di(dicyclohexylphosphino)butane, 1,5-di(dinaphthylphosphino)pentane, 1 ,3-di(di-p-tolylphosphino)propane, 1 ,4-di(di-p-methoxyphenylphosphino)butane, 1,2-di(diphenylphosphino)ethene, 2,3-di(diphenylphosphino)-2-butene, 1,3-di(diphenylphosphino)-2-oxopropane, 2-methyl-2-(methyldi phenylphosphino)-l ,3-di(diphenyl phosphino)propane, o,o'-di(diphenylphospino)biphenyl, 1,2-di(diphenylphosphino)benzene, 2,3-di(diphenylphosphino)naphthalene, 1,2-di(diphenylphosphino)cyclohexane, 2,2-dimethyl-4,5-di(diphenylphosphino)dioxolane and

Very good results have been obtained with 1,3-di(diphenylphosphino)propane.

The bidentate ligand can be used in quantities, relative to the palladium compound, that can rangewithin wide limits, e.g.from 0.1 to 10 mol per mol palladium compound. Preferred quantities range from 0.3to3and particularlyfrom 1 to 3 mol per mol.

If desired, one or more monodentate ligands can also be used in the preparation of the catalysts. Suitable monodentate ligands are in particulartriarylphosphines, such as optionally substituted triphenylphosphines.

According to a preferred embodiment the process according to the present invention is carried out in the presence of hydrogen. It has surprisingly been found that the presence of hydrogen has a stronglyaccelerat- ing effect on the rate of reaction. Preferably, a molar ratio carbon monoxide to hydrogen in the range offrom 0.8to 20 is used, the reaction rate being very high and only a minor amount of polyketones being formed. The selection ofthis range is surprising, because according to European patent application 121965 for the preparation of polyketones it is generally desirable to select a value above 2/3 for this molar ratio. Said molar ratio is most preferably in the range offrom 0.9 to 10.The molar ratio maybe higherthan 20, for example upto 2odor lower than 0.8, for example at least 0.1.

The carbon monoxide and the hydrogen can be used in pure form or diluted with an inert gas such as nitrogen, noble gases or carbon dioxide in the process according to the invention.

The process ofthis invention is preferably carried out at a temperature in the range offrom 20"C to 200"C, in particular 50to 150 OC, and total pressure in the range offrom 2to 100, in particular 20 to 75 bar. It can be carried out batchwise, continuously or semi-continuously. In general, reaction times between 1 and 20 hours appearto be adequate.

The process according to the invention is suitably carried out in the presence of an aprotic solvent. Examples of such solvents are hydrocarbons, such as hexane, octane, benzene, toluene, the three xylenes, ethylbenzene, cumene and cyclohexane; halogenated hydrocarbons, such as chloroform, 1,2- dichloroethane, perfluoroalkanes, chlorobenzene and the three dichlorobenzenes; sulphones such as diethyl sulphone, diisopropyl sulphone and tetrahydrothiophene 1,1-dioxide (also referred to as "sulfolane");N,Ndialkyl-substituted amides such as N,N-dimethylformamide and N-methylpyrrolidone; esters such as methyl benzoate, ethyl acetate and amyl acetate; ethers such as diethyl ether, 3,6-dioxaoctane, methyl tert.- butylether, tetrahydrofuran, diisopropyl ether, 1,4-dioxane, 2,5,8-trioxanonane (also referred to as "diglyme"), diphenyl ether and anisole. Very good results have been obtained with ethers.

The monoketones formed by the process according to the present invention may be isolated from the reaction mixture in any suitable manner, for example by means of distilation, obtaining a distillate fraction containing the monoketones, and a bottom fraction containing the catalytic system. Suitably, an aprotic solvent is chosen that substantiaily remains in the bottom fraction. Preferably, at least a portion of the bottom fraction containing aprotic solvent and catalytic system is re-used in the process according to the invention.

The following Examples further illustrate the invention.

Example 1 A magnetically stirred 300 ml autoclave was charged with diglyme (50 ml), palladium (Il) acetate (0.1 mmol), 1,3-di(diphenylphosphino)propane (0.15 mmol) and p-toluenesulphonicacid (2 mmol).Theauto- ciave was flushed with carbon monoxide, charged with carbon monoxide until a partial pressure thereof of 20 bar was reached, charged with propene until a partial pressure thereof of 10 bar was reached, sealed and heated ata temperature of 135 C.

Analysis ofthe reaction product by means of gas-liquid mass spectroscopy showed that the rate of reaction was 200 gram of products per gram of palladium per hour. The composition of the products, expressed in per cent by weight, is stated in the Table hereinafter. The products were isolated by means of distillation.

TABLE

Products Example, 1 2 3 Isopropenyl propyl ketone isoropenyl isopropyl ketone 1-propenyl propyl ketone 2-propenyl propyl ketone 70 65 37 1-propenyl isopropyl ketone 2-propenyl isopropylketone isopropyl propyl ketone diisopropyl ketone 20 25 33 dipropylketone polyketones J 10 10 30 Example 2 Example 1 was repeated with the difference that the autoclave was also charged with hydrogen until a partial pressure thereof of 5 bar was reached, the molar ratio CO: H2 being 4.

The rate of reaction was 500 gram of products per gram of palladium per hour. Comparison with Example 1 showsthatthe presence of merely 5 bar of hydrogen has a strongly accelerating effect on the reaction. The composition ofthe products is stated in the Table hereinbefore.

Example 3 Example 1 was repeated with the difference that the autoclave was also charged with hydrogen until a partial pressure thereof of 20 bar was reached, the molar ratio CO : H2 being 1 The rate of reaction was 1000 gram of products per gram of palladium per hour. Comparison with Example 2 shows thatthe pressure of 20 bar of hydrogen promotes the reaction even further. The composition ofthe products is stated in the Table hereinbefore. Comparison ofthe compositions obtained in Examples 2 and 3 shows that increasing the molar ratio hydrogen to carbon monoxide from 0.25 to 1 results in less monoketones and more higheroligomers.

Claims

1. A process for the preparation of a mixture comprising alkenically unsaturated monoketones and dia Ikylmonoketones, all monoketones having the same number of carbon atoms in the groups bound to the carbonyl group which process comprises reacting carbon monoxide with an alkene having at leastthree carbon atoms per molecule and having the same number of carbon atoms as each ofthe groups bound to said carbonyl group in the presence of a catalytic system prepared by combining::- a) palladium and/ora palladium compound, b) an acid having a pKa of less than 2, provided it is neither a hydrohalogenic acid nor carboxylic acid, and c) a bidentate ligand of the general formula I R1R2-M-R-M-R3R4 (l) in which M represents a phosorous, arsenic or antimony atom, R represents a divalent organic bridging group having at leasttwo carbon atoms in the bridge, none of these carbon atoms carrying su bstituents that may cause steric hindrance and in which R1, R2, R3 and R4 represent identical or different optionallysubstituted hydrocarbon groups, followed by isolation ofsaid monoketones from the reaction mixture thus obtained.

2. A process as claimed in claim 1 in which the anion ofthe acid having a pKa of less than 2 is noncoordinating.

3. A process as claimed in claim 2 in which the acid is a sulphonic acid or an acid that can beformedby interacting a Lewis acid with a Broensted acid.

4. A process as claimed in claim 1 or 2 in which an acid is used having the general formula II

in which X represents a sulphur or chlorine atom and, if X represents a chlorine atom, R5 represents an oxygen atom and, if X represents a sulphur atom, R5 represents an OH group or an optionallysubstituted hydrocarbon group.

5. A process as claimed in claim 4 in which the hydrocarbon group R5 is an alkyl, aryl, aralkyl oralkaryl group with 1-30 carbon atoms.

6. A process as claimed in claim 4 or 5 in which p-toluenesulphonic acid ortrifluoromethanesulphonic acid is used.

7. Aprocess as claimed in anyone ofthe preceding claims in which group -R-represents a group.

in which R6 and R7 represent hydrogen atoms or optionally substituted hydrocarbon groups offering no steric hindrance and n isan integerofatleast2.

8. A process as claimed in claim 7 in which n is an integer of not more than 5.

9. A process as claimed in any one of the preceding claims in which the hydrocarbon groups R1, R2, R3 and R4are optionally substituted aryl groups with 6-14 carbon atoms.

10. A process as claimed in claim 9 in which the aryl groups are optionally substituted phenyl groups.

11. A process as claimed in claim 10 in which the bidentate ligand is 1 ,3-di(diphenylphosphino)propane.

12. A process as claimed in any one of the preceding claims in which 0.3-3 mol bidentate ligand per gram atom palladium is used.

13. A process as claimed in any one ofthe preceding claims in which the alkene has less than 30 carbon atoms per molecule.

14. A process as claimed in claim 13 in which the alkene has less than 10 carbon atoms per molecule.

15. A process as claimed in claim 14 in which the alkene is propene.

16. A process as claimed in any one ofthe preceding claims which is carried out in the presence of hydrogen.

17. Aprocess as claimed in claim 16 in which a molar ratio carbon monoxide to hydrogen in the rangeof from 0.8 to 20 is used.

18. A process as claimed in claim 17 in which said molar ratio is in the range offrom 0.9 to 10.

19. A process as claimed in anyone ofthe preceding claims which is carried out in the presence of an aprotic solvent.

20. A process as claimed in claim 19 in which the aprotic solvent is an ether.

21. A process as claimed in anyone ofthe preceding claims which is carried outatatemperature in the range of from 20 "C to 200 "C.

22. A process as claimed in any one ofthe preceding claims which is carried outata pressure in the range of from 2 to 100 bar.

23. A process as claimed in any one of the preceding claims in which the reaction mixture obtained is separated by distillation into a distillate fraction containing the monoketones and a bottom fraction containing the catalytic system, and at least a portion of the bottom fraction is re-used in the process.

24. A process as claimed in claim 1 substantially as hereinbefore described with reference to any one of the Examples 1,2 and 3.

25. Alkenically unsaturated monoketones and dialkylmonoketones, all monoketones having the same numberof carbon atoms in the groups bound to the carbonyl group whenever prepared by a process as claimed in any one of the preceding claims.