GB2251855A - Preparation of thiol esters - Google Patents

Preparation of thiol esters Download PDF

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Publication number
GB2251855A
GB2251855A GB9100793A GB9100793A GB2251855A GB 2251855 A GB2251855 A GB 2251855A GB 9100793 A GB9100793 A GB 9100793A GB 9100793 A GB9100793 A GB 9100793A GB 2251855 A GB2251855 A GB 2251855A
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Prior art keywords
phosphine
acid
thiol
palladium
source
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GB9100793A
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GB9100793D0 (en
Inventor
Eit Drent
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Shell Internationale Research Maatschappij BV
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Shell Internationale Research Maatschappij BV
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Priority to GB9100793A priority Critical patent/GB2251855A/en
Publication of GB9100793D0 publication Critical patent/GB9100793D0/en
Publication of GB2251855A publication Critical patent/GB2251855A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J31/2409—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J31/2409—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom
    • B01J31/2414—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom comprising aliphatic or saturated rings
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C327/00—Thiocarboxylic acids
    • C07C327/20—Esters of monothiocarboxylic acids
    • C07C327/22—Esters of monothiocarboxylic acids having carbon atoms of esterified thiocarboxyl groups bound to hydrogen atoms or to acyclic carbon atoms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/30—Addition reactions at carbon centres, i.e. to either C-C or C-X multiple bonds
    • B01J2231/32—Addition reactions to C=C or C-C triple bonds
    • B01J2231/321—Hydroformylation, metalformylation, carbonylation or hydroaminomethylation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
    • B01J2531/82—Metals of the platinum group
    • B01J2531/824—Palladium

Abstract

The invention relates to a process for the preparation of a thiol ester, which comprises reacting an acetylenically unsaturated compound with carbon monoxide and a thiol in the presence of a catalyst system comprising: a) a source of palladium cations, b) a phosphine, and c) a source of anions derived from strong protonic acids, except hydrohalogenic acids.

Description

PREPARATION OF THIOL ESTERS This invention relates to a process for the preparation of thiol esters.
It is known that thiol esters may be prepared by reacting an acetylenically unsaturated compound with carbon monoxide and a thiol in the presence of a carbonylation catalyst.
U.S. patent specification number 3,933,884 discloses a process in which a l-alkene or l-alkyne is reacted with carbon monoxide and a thiol in the presence of a ligand-stabilized noble-metal halide catalyst, in conjunction with Group IVB metal halide co-catalysts.
In Example 17 only, a carbonylation of an acetylenically compound is exemplified. However, this experiment was conducted in a qualitative manner without indication of attainable conversion rates or selectivities, leaving doubts whether this process provides an economically acceptable route to thiol esters of unsaturated carboxylic acids.
It has now been found that thiol esters of unsaturated carboxylic acids may be prepared with attractive yields and selectivities using a particular palladium/phosphine-based catalyst system. Surprisingly, high reaction rates were observed at relatively low temperature, without significant formation of side-products.
Accordingly, the present invention provides a process for the preparation of a thiol ester, which comprises reacting an acetylenically unsaturated compound with carbon monoxide and a thiol in the presence of a catalyst system comprising: a) a source of palladium cations, b) a phosphine, and c) a source of anions derived from strong protonic acids, except hydrohalogenic acids.
The acetylenically unsaturated compound used in the process according to the invention may be an unsubstituted or a substituted alkyne or cycloalkyne. It preferably has from 2 to 30, more preferably 2 to 20 carbon atoms, and from 1 to 3 triple bonds, more preferably 1 triple bond. When the acetylenically unsaturated compound is a substituted alkyne or cycloalkyne, the alkyne or cycloalkyne may be substituted by, for example, one or more atoms or groups selected from a halogen atom, and a cyano, acyl, acyloxy, alkyl, alkoxy, haloalkoxy, carboxy, aryl, haloalkyl, acylamido, amino, thiol and hydroxyl group. It will be appreciated that some of these groups may react under the conditions of the process.
Examples of suitable acetylenic compounds are ethyne, propyne, l-butyne, 2-butyne, the isomeric pentynes, hexynes, octynes and dodecynes, and phenylethyne.
Preferably the acetylenically unsaturated compound is an alpha-acetylenically unsaturated compound, for example a l-alkyne.
The thiol used in the process according to the invention may be aliphatic or aromatic and may be unsubstituted or substituted with one or more substituents, such as those mentioned above in connection with the acetylenically unsaturated compounds. It preferably has up to 20, more preferably up to 10 carbon atoms. One or more thiol (SH) groups may be present.
Examples of suitable thiols include alkylthiols, for instance, methanethiol, ethanethiol, l-propanethiol, 2-propanethiol, l-butanethiol, 2-methylpropane-2-thiol, l-pentanethiol and l-hexanethiol, cyclohexanethiol, and alkane dithiols, for instance, 1,2-ethane dithiol and 1,4-butane dithiol.
It will be appreciated that the acetylenically unsaturated compound and the thiol may be the same compound.
The catalyst system employed in the process according to the invention comprises a source of palladium cations. Without wishing to be bound by any theory, it is believed that a cationic complex of palladium with the phosphine is generated in the catalyst system.
The source of palladium cations is preferably a salt of palladium. Examples of salts include salts of nitric acid; sulphuric acid; sulphonic acids, for instance, chlorosulphonic acid, methanesulphonic acid, trifluoromethanesulphonic acid, t-butylsulphonic acid, p-toluenesulphonic acid or a sulphonated ion exchange resin; and a carboxylic acid, for example an alkanoic acid such as acetic acid. Since halide ions can be corrosive, the source of palladium cations is preferably not a halide.
It will be appreciated that when the source of palladium cations is a salt of palladium, the palladium may be present in a complex, for example with a phosphine.
The source of palladium cations may also be palladium metal, or a compound of palladium other than a salt. For example, it may be an oxide or a zerovalent complex with a ligand such as a phosphine or carbon monoxide. In this case, palladium cations are generated in situ in the catalyst system by reaction with a protonic acid used as anion source.
The quantity of the source of palladium cations employed in the process according to the invention is not critical. Preferably it is sufficient to provide in the range of from 10 7 to 10 1 gram atoms of palladium cations per mole of acetylenically unsaturated compound, more preferably from 10 ó to 10 2 gram atoms per mole.
The phosphine employed in the process according to the invention may be a monodentate or bidentate phosphine, and generally is a phosphine of formula R2P-A with any R independently representing an organic group, and A being R or representing a group -X-PR2, in which X is a bridging group having up to 10 atoms in the bridge, for example an alkylidene or oxalkylidene group, which may or may not be substituted by substituents, which will not sterically hinder bidentate complex formation.
Suitable monodentate phosphines can be represented as R123 1 2 3 phosphines of formula R1R2R3P, in which each of R1, R2 and R3 independently represents an optionally substituted alkyl, cycloalkyl, aryl, or imino-containing heterocyclic group.
Suitable bidentate phosphines can be represented as phosphines of formula R1R2P-X-PR3R4, in which each of Rl R2 R3 and R4 independently represents an optionally substituted alkyl, cycloalkyl, aryl, or imino-containing heterocyclic group.
When a group is said to be optionally substituted, it may be substituted by one or more substituents selected from the group including halogen atoms, alkyl groups, alkoxy groups, haloalkyl groups, haloalkoxy groups, acyl groups, acyloxy groups, amino groups, hydroxyl groups, nitrile groups, acylamino groups, and aryl groups.
An alkyl group, as such or in an alkoxy or acyl group, is preferably a C1-10 alkyl group, more preferably a C16 alkyl group.
Examples of alkyl groups are methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl and tert-butyl. A cycloalkyl group is preferably a C36 alkyl group, for example cyclopentyl or cyclohexyl. An aryl group is preferably a phenyl or a naphthyl group.
As used herein, the term "imino" means a nitrogen atom which may be represented in the structural formula of the heterocyclic group containing it by the formula N- . The imino-containing heterocyclic group is preferably a 6-membered ring containing one, two or three nitrogen atoms, and is preferably connected to a phosphorus atom through a single bridging carbon atom. For example, if the heterocyclic group is a pyridyl group, it is preferably connected through the carbon atom at the 2-position in the pyridyl group. Examples of imino-containing heterocyclic groups are pyridyl, pyrazinyl, quinolyl, isoquinolyl, pyrimidinyl, pyridazinyl, cinnolinyl, triazinyl, quinoxalinyl, and quinazolinyl.
Pyridyl and pyrimidinyl are preferred.
Monodentate or bidentate phosphines being substituted by at least one imino-containing heterocyclic group are particularly preferred in the present process.
Phosphines suitable in the present process include tri(n-butyl)phosphine, triphenylphosphine, tri(o-tolyl)phosphine, ethyldiphenylphosphine, tri(p-methoxyphenyl)phosphine, tricyclohexylphosphine, and 1,3-di(diphenylphosphino)propane. Preferred phosphines include diphenyl-2-pyridylphosphino, phenyl-bis (2-pyridyl)phosphine and 1, 3-di(phenyl-2-pyridylphosphino)propane.
The quantity of phosphine used in the present process is conveniently in the range of from 0.5 to 100 moles per gram atom of palladium cations. Particularly good results have been obtained using from 1 to 30 moles of phosphines per gram atom of palladium cations.
The catalyst system used in the process according to the invention further comprises the anion derived from a strong acid, particularly an acid having a pKa < 3, preferably < 2, (measured at 18 "C in aqueous solution), except hydrohalogenic acids. Said anions preferably have no or weakly coordinative tendency towards palladium, by which is meant that little or no covalent interaction takes place between the palladium cation and the strong acid-derived anion.
The required source of anions may be constituted by a corresponding salt or by the corresponding acid. In particular, the anions may be provided by selecting the corresponding palladium salt when preparing the catalyst system. The corresponding acid may be added in stoichiometric amounts or in excess relative to the amount of palladium, more particularly in amounts up to 100 equivalents of acid per gram atom of palladium.
Suitable acids from which the required anions are derived, include sulphuric acid, nitric acid, orthophosphoric acid; perhalic acids, for instance, perchloric acid; sulphonic acids, for instance fluorosulphonic acid, chlorosulphonic acid, methanesulphonic acid, 2-hydroxypropanesulphonic acid, 4-butylsulphonic acid, p-toluenesulphonic acid, benzenesulphonic acid, l-naphthalenesulphonic acid, trifluoromethanesulphonic acid or a sulphonated ion exchange resin; or an acid derived by interaction of a Lewis acid, for instance BF3, AsF5, SbF5, TaF5 or NbF5, with a Broensted acid, for instance HF, for example fluorosilicic acid, HBF4, HPF5 and HSbF6. Particularly good results have been achieved using a sulphonic acid.
The catalyst system used in the process according to the invention may be homogeneous or heterogeneous (an example of a heterogeneous catalyst system is one comprising a sulphonate ion exchange resin). Preferably it is homogeneous.
The catalyst system is constituted in a liquid phase. The liquid phase may conveniently be formed by one or more of the reactants with which the catalyst system is to be used. It may also be formed by a solvent, or by one of the components of the catalyst system.
If it is desired to employ a solvent in the process according to the invention, this may be, for instance, a sulphoxide or sulfone (e.g. dimethylsulphoxide, diisopropylsulphone or tetrahydrothiophene-2,2-dioxide-also known as sulpholane, 2-methylsulpholane, 3-methylsulpholane, 2-methyl-4-butylsulpholane; an aromatic hydrocarbon such as benzene, toluene, the xylenes; an ester such as methylacetate; a ketone such as acetone or methylisobutylketone; an ether such as anisole or 2,5,8-trioxanonealso known as diglyme, diphenylether or diisopropylether; or an amide such as dimethylacetamide or N-methylpyrrolidone. The reaction is preferably performed in the presence of a solvent which is an amide.
The reaction between the acetylenically unsaturated compound, carbon monoxide and the thiol is preferably effected at a temperature in the range of from 10 "C to 200 "C, in particular from 20 "C to 120 "C. The pressure is preferably in the range of from 1 to 70 bar. Pressures higher than 100 bar may be used, but are generally economically unattractive because of the need for special apparatus.
The molar ratio of the acetylenically unsaturated compound to the thiol is not critical. Conveniently it is in the range of from 0.01:1 to 100:1.
The process according to the invention may be operated batchwise or continuously.
The carbon monoxide used in the process according to the invention may be in a substantially pure form or diluted with an inert gas, for example nitrogen. Preferably the quantity of any hydrogen present is less than 5 vol%, in order to avoid hydrogenation of the acetylenically unsaturated compound.
The invention will now be illustrated by the following Example.
Example A 250 ml magnetically-stirred stainless steel autoclave was charged with 0.1 mmol palladium (II) acetate, 3 mmol diphenyl2-pyridylphosphine, 2 mmol paratoluenesulfonic acid, 40 ml N-methylpyrrolidine (NMP), and 20 ml n-pentanethiol. Air was evacuated from the autoclave, whereupon 30 ml of propyne was introduced. Subsequently, carbon monoxide was added to a pressure of 56 bar. The autoclave was then sealed and heated to a temperature of 70 "C. After two hours of reaction, a sample of the contents of the autoclave was analyzed by gas liquid chromatography. From the results of the analysis, the selectivity to the l-pentanethiol ester of methacrylic acid was calculated to be 100% (based on thiol), and the mean conversion rate was calculated to be 1000 moles thiol/gram atom of palladium/hour.

Claims (16)

1. A process for the preparation of a thiol ester, which comprises reacting an acetylenically unsaturated compound with carbon monoxide and a thiol in the presence of a catalyst system comprising: a) a source of palladium cations, b) a phosphine, and c) a source of anions derived from strong protonic acids, except hydrohalogenic acids.
2. A process as claimed in claim 1, wherein the source of palladium cations is a salt of palladium.
3. A process as claimed in claim 1 or claim 2, wherein the phosphine is a phosphine of formula R2P-A with any R independently representing an organic group, and A being R or representing a group -X-PR2, in which X is a bridging group having up to 10 atoms in the bridge.
4. A process as claimed in claim 3, wherein the phosphine is a R123 1 2 monodentate phosphine of formula R R R P, in which each of R , R 3 and R3 independently represents an optionally substituted alkyl, cycloalkyl, aryl, or imino-containing heterocyclic group.
5. A process as claimed in claim 4, wherein at least one of R1, R2, and R represents an optionally substituted imino-containing heterocyclic group.
6. A process as claimed in claim 3, wherein the phosphine is a bidentate phosphine of formula R1R2P-X-PR3R4, in which each of R1, R , R3 and R independently represents an optionally substituted alkyl, cycloalkyl, aryl, or imino-containing heterocyclic group.
7. A process as claimed in claim 6, wherein at least one of R1, R , R and R represents an optionally substituted imino-containing heterocyclic group.
8. A process as claimed in any one of claims 1 to 7, wherein the protonic acid has a pKa of less than 3.
9. A process as claimed in any one of claims 1 to 8, wherein the pro tonic acid is a sulfonic acid.
10 A process as claimed in any one of claims 1 to 9, wherein the source of anions is an acid.
11. A process as claimed in claims 10, wherein the number of equivalents of acid per gram atom of palladium cations is below 100.
12. A process as claimed in any one of claims 1 to 11, wherein the reaction is effected at a temperature in the range of from 20 to 120 "C, and a pressure in the range of from 1 to 70 bar.
13. A process as claimed in any one of claims 1 to 12, wherein the acetylenically unsaturated compound is an alpha-unsaturated compound having from 3 to 20 carbon atoms.
14. A process as claimed in any one of claims 1 to 13, wherein the thiol has up to 10 carbon atoms.
15. A process for the preparation of a thiol ester, substantially as described hereinbefore with reference to the Example.
16. A thiol ester whenever prepared by a process according to any one of claims 1-15.
GB9100793A 1991-01-15 1991-01-15 Preparation of thiol esters Withdrawn GB2251855A (en)

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GB2251855A true GB2251855A (en) 1992-07-22

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3933844A (en) * 1970-08-26 1976-01-20 Fisons Limited Benzopyranyltetrazoles

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3933844A (en) * 1970-08-26 1976-01-20 Fisons Limited Benzopyranyltetrazoles

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