WO2011006667A2 - Non-leaching heterogeneous catalyst systems for coupling reactions - Google Patents

Non-leaching heterogeneous catalyst systems for coupling reactions Download PDF

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Publication number
WO2011006667A2
WO2011006667A2 PCT/EP2010/004347 EP2010004347W WO2011006667A2 WO 2011006667 A2 WO2011006667 A2 WO 2011006667A2 EP 2010004347 W EP2010004347 W EP 2010004347W WO 2011006667 A2 WO2011006667 A2 WO 2011006667A2
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accordance
group
catalyst system
supported catalyst
ligand
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PCT/EP2010/004347
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WO2011006667A3 (en
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Heidrun Gruber-Woelfler
Johannes Khinast
Paul Radaschitz
Peter Feenstra
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Technische Universität Graz
Forschungsholding Tu Graz Gmbh
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Priority to DE112010005708T priority Critical patent/DE112010005708T5/en
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Publication of WO2011006667A3 publication Critical patent/WO2011006667A3/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
    • B01J31/1616—Coordination complexes, e.g. organometallic complexes, immobilised on an inorganic support, e.g. ship-in-a-bottle type catalysts
    • B01J31/1625—Coordination complexes, e.g. organometallic complexes, immobilised on an inorganic support, e.g. ship-in-a-bottle type catalysts immobilised by covalent linkages, i.e. pendant complexes with optional linking groups
    • B01J31/1633—Coordination complexes, e.g. organometallic complexes, immobilised on an inorganic support, e.g. ship-in-a-bottle type catalysts immobilised by covalent linkages, i.e. pendant complexes with optional linking groups covalent linkages via silicon containing groups
    • 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
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
    • B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
    • B01J29/0316—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing iron group metals, noble metals or copper
    • B01J29/0325—Noble metals
    • 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
    • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
    • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
    • 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
    • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
    • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
    • B01J31/181—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine
    • B01J31/1815—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine
    • B01J31/182—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine comprising aliphatic or saturated rings
    • 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
    • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
    • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
    • B01J31/181—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine
    • B01J31/1825—Ligands comprising condensed ring systems, e.g. acridine, carbazole
    • B01J31/183—Ligands comprising condensed ring systems, e.g. acridine, carbazole with more than one complexing nitrogen atom, e.g. phenanthroline
    • B01J31/1835—Ligands comprising condensed ring systems, e.g. acridine, carbazole with more than one complexing nitrogen atom, e.g. phenanthroline comprising aliphatic or saturated rings
    • 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
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
    • B01J2231/4205—C-C cross-coupling, e.g. metal catalyzed or Friedel-Crafts type
    • 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
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
    • B01J2231/4205—C-C cross-coupling, e.g. metal catalyzed or Friedel-Crafts type
    • B01J2231/4211—Suzuki-type, i.e. RY + R'B(OR)2, in which R, R' are optionally substituted alkyl, alkenyl, aryl, acyl and Y is the leaving group
    • 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
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
    • B01J2231/4277—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues
    • B01J2231/4283—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues using N nucleophiles, e.g. Buchwald-Hartwig amination
    • 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
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
    • B01J2231/4277—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues
    • B01J2231/4288—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues using O nucleophiles, e.g. alcohols, carboxylates, esters
    • 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
    • B01J2531/02—Compositional aspects of complexes used, e.g. polynuclearity
    • B01J2531/0238—Complexes comprising multidentate ligands, i.e. more than 2 ionic or coordinative bonds from the central metal to the ligand, the latter having at least two donor atoms, e.g. N, O, S, P
    • B01J2531/0241—Rigid ligands, e.g. extended sp2-carbon frameworks or geminal di- or trisubstitution
    • B01J2531/0244—Pincer-type complexes, i.e. consisting of a tridentate skeleton bound to a metal, e.g. by one to three metal-carbon sigma-bonds
    • 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

Definitions

  • the present invention relates to non-leaching catalysts for C-C, C-O or
  • Catalytic C-C. C-O or C-N couplings represent versatile methods for the preparation of a wide variety of different products, including intermediates and final products in the pharmaceutical area and other fields.
  • Metal catalysts are generally used for these reactions and accordingly, metal catalyzed reactions have become part of the standard repertoire of the synthetic chemist.
  • Suzuki and Heck reactions are frequently carried out with palladium based catalyst systems. These two reactions are especially versatile one step methods for the preparation of complex structures as they can be found e.g. in
  • homogeneous catalyst systems are frequently composed of a metal/ligand system where these components are in a particular stoichiometric ratio with respect to one another. This makes the
  • WO 2006/094392 discloses a catalyst comprising a functionalized silica gel material and a metal wherein the silica material is functionalized by co-condensation with a functionalizing agent, preferably selected from thiols or amines. 3-Mercaptopropyltrimethoxysilane is a preferred functionalizing agent.
  • WO 2006/121553 describes and claims a process for the manufacture of supported nanocatalysts wherein functionalizing agents for functionalizing the surface of a carrier material have at least two functional groups, one for the attachment to the surface of a carrier and the other functional group for attachment to the metal.
  • the catalyst is prepared in two subsequent steps. In the first step, one of the functional groups of the functionalizing agent is attached to the carrier or support material and thereafter the catalytically active metal is attached to the remaining functional group of the functionalizing agent.
  • the catalytic metal is copper and the coordinative immobilization as well as the covalent attachment of the ligand to the support is described.
  • the catalyst systems are useful in asymmetric catalysis in a variety of enantioselective reactions.
  • WO -A 2007/102334 discloses polysilane or polysilane/inorganic material supported transition metal catalysts. According to the teaching of the reference a strong binding interaction between the catalyst metal and the support is considered disadvantageous compared to a metal supported only by adsorption or ionic binding as the former prevents the release of the metal. This clearly indicates that the active species of the catalyst is dissolved metal and thus all problems associated with homogenous catalyst outlined above also apply to the catalysts of this reference.
  • EP -A 1186583 relates to a method for carrying out C-C coupling
  • R is hydrogen or methyl were used for the coupling of aryl bromides and phenylboronic acid according to the general reaction scheme Il
  • a further object of the invention was the use of the novel catalysts for C-C, C-O and C-N coupling reaction, in particular for so called Suzuki- and Heck-reactions.
  • the catalyst systems in accordance with the invention comprise as
  • component a) an inorganic support material can be selected from any inorganic material known to those skilled in the art for supporting catalyst particles, in particular catalyst particles comprising Pd as active metal.
  • Suitable supports of this type include alumina, silica, silica gel, titania, kieselguhr, diatomaceous earth, bentonite, clay, zirconia, magnesia as well as oxides of other metals.
  • porous solids such as for example natural and synthetic zeolites or other materials which have ordered or quasi ordered pore structures. In those cases where porous solids are used it is preferred to use materials having a surface area according to BET of more than 20 m 2 /g, preferably of more than 50 m 2 /g.
  • Preferred inorganic support materials are silicates of the general formula RO 4 ⁇ Si - A q , wherein q is an integer of from 0 to 4,
  • R is hydrogen or an organic group selected from:
  • alkylcarbonyloxy arylcarbonyloxy, alkoxycarbonyloxy, alkylcarbonyl, alkoxycarbonyl, alkylthiocarbonyl, phosphonato, phosphinato, heterocyclyl and esters thereof, and
  • A is a hydrolyzable group selected from OR, halogen phosphate, phosphate ester, alkoxycarbonyl, hydroxyl, sulfate and sulfonato.
  • Preferred members of this group are tetraethoxysilane and silsesquioxane.
  • R is as defined above and R' is a bridging group selected from alkylene or arylene, e.g. methylene, ethylene, propylene, ethenylene, phenylene, biphenylene or heterocyclyl.
  • a preferred bridging group is 1 ,4-phenylene.
  • a particularly preferred group of inorganic materials is so called mesoporous silica.
  • the most common types of these mesoporous nanoparticulate materials are MCM-41, FSM-16 and SBA-15.
  • Mesoporous silica nanoparticles were first synthesized in 1990 by researchers in Japan (Yanagisawa et al., Bull.Chem.Soc.Japan., 63, 1990, pp 988ff) and later produced at Mobile Corporation (Beck et al., J.A.C.S. 114, 10834ff).
  • WO 1992/06921 discloses synthesis and properties of a number of MCM materials suitable for the instant invention as inorganic support material.
  • Mesoporous silica nanoparticles are generally synthesized by reacting tetra ethyl orthosilicate with a template of micellar rods. The result is usually a collection of nano-sized spheres with a regular arrangement of pores. The template can then be removed by washing with a solvent. Respective procedures are described in the literature and known to the man skilled in the art.
  • MCM-41, FSM-16 and SBA-15 as two particularly preferred examples of this type are available from commercial sources.
  • the catalyst system comprises as component b) a modifying agent
  • the modifying group is covalently bonded to said inorganic support material through at least one first functional group FG 1 and provides at least one second functional group FG2 for bonding a ligand thereto.
  • Suitable modifying agents are compounds that include functional groups undergoing a reaction with bonding sites on the support material.
  • the modifying agents include molecules having at least two functional groups, which can be the same or different.
  • the at least one second functional group FG2 is selected to promote the bonding of a ligand thereto.
  • Modifying agents suitable for use in the instant invention include a variety of organic molecules as well as polymers and oligomers.
  • exemplary of suitable bifunctional agents are diacids such as oxalic acid, malonic acid, maleic acid, succinol acid and the like; dialcohols such as 1 ,2-ethane diol, 1 ,2-propanediol and 1 ,3-propandiol; hydroxyl acids such as glycolic acid, lactic acid and the like.
  • Suitable polyfunctional compounds include sugars polyfunctional carboxylic acids and hydroxyl diacids.
  • Suitable modifiying agents include ethanolamine, mercaptoethanol, 2-mercaptoacetate, amino acids, sulfonic acids, sulfobenzyl alcohol and other sulfobenzoyl compounds as well as in general compounds comprising amino and thiol functional groups.
  • Modifying agents can also be oligomers and polymers comprising a
  • oligomers or polymers are polyacrylates, polyvinylbenzoates, polyvinyl sulfate, polyvinylsulfonates or generally sulfonated polmers.
  • modifying agents b) for the modification of the preferred silicas as component a) compounds of the general formula X 3 ⁇ G e Si - R" -Y, wherein e is an integer between 0 and 2, X is a group capable of undergoing condensation, e.g. alkoxy or a group OG, halogen, allyl, phosphate, phosphate ester, alkoxycarbonyl, hydroxyl, sulfate and sulfonate,
  • G is an organic group, e.g. C 1 - C 2 o— alkyl Or - C 1 - C 2 o -alkenyl (in each case straight chain, branched, substituted or unsubstituted), aryl or heteroaryl (in each case substituted or unsubstituted) and
  • alkylcarbonyloxy arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, alkylcarbonyl, alkoxycarbonyl, alkylthiocarbonyl, phosphonato,
  • R" is selected from an aliphatic group -(CH 2 ) b , wherein one or more of the hydrogen atoms on the methylene group may be substituted so that R" may be linear, branched, cyclic or unsaturated aliphatic or wherein R" is arylene, preferably 1 ,4-phenylene, and
  • Y is a functional group based on one of the following elements: S, N, O, C 1 H, P 1 Si or halogen including , inter alia, SH, NH 2 , PO(OH) 2 , NHCSNH 2 , NHCONH 2 , SG, NHG 1 PG 3 , PO(OG) 2 , NG 2 , imidazole, benzimidazole, thiazole, halogens and silanes.
  • Particularly preferred modifying agents b) are mercaptopropyltrimethoxysilane [(CH 3 O) 3 Si(CH 2 ) 3 SH)], aminopropyltriethoxysilane [(C 2 H 5 O) 3 Si(CH 2 J 3 NH 2 )], and
  • Particularly prefereed is a combination of either MCM-41 , FSM-16 or SBA-15 as inorganic support material a) with either of mercaptopropyltrimethoxysilane [(CH 3 O) 3 Si(CHz) 3 SH)], aminopropyltriethoxysilane [(C 2 H 5 O) 3 Si(CH 2 J 3 NH 2 )], and aminopropyltrimethoxysilane [(CH 3 O) 3 Si(CH 2 J 3 NH 2 )] as modifying agent b).
  • a ligand is covalently bound to the at least one second functional group of the modifying agent which is available for ligand bonding, i.e. which is not involved in the attachment of the modifying agent to the inorganic support material.
  • the ligand is covalently bound to the functional group rather than only attached through a coordinating bond. This improves the capability of the inventive catalyst systems to immobilize the palladium metal which is important relating to the work- up of the reaction product in reactions catalyzed with the inventive catalyst systems.
  • the ligand comprises a spacer group of at least four (4), preferably at least five and particularly preferably at least 6 carbon atoms between the atom of the ligand bound to the functional group FG2 of the modifying agent b) and the place of attachment of the palladium compound. If the spacer group is shorter than four carbon atoms an interaction between the support material and the palladium metal may occur, which may have a detrimental influence on the catalytic
  • part or all of the palladium metal may undergo direct bonding of the palladium metal to the inorganic support, which may also be
  • the spacer provided by the ligand exceeds a certain number of carbon atoms, e.g. 7 to 9 carbon atoms, it may be beneficial to use a ligand where the rigidity of the spacer chain is enhanced by e.g. multiple bonds or substituents limiting the moveability of the spacer chain by steric hindering, e.g. voluminous substituents on the spacer chain forcing the ligand molecule into a fixed steric configuration.
  • Preferred spacer groups are alkylene groups -CH 2 — and the preferred chain length is between 6 and 15, preferably between 8 and 12 carbon atoms.
  • the hydrogen atoms of the alkylene groups may be partly replaced by the aforementioned substituents providing a certain stereochemical configuration of the molecule.
  • condensed aryl or heteraryl or carbocyclyl or heterocyclyl substituents may be mentioned. Suitable substituents of this type are know to the skilled man so that there is no need for a detailed description herein.
  • systems according to the invention comprises at least two sp 2 - hybridized nitrogen atoms to which the active catalyst metal, i.e. the palladium is attached.
  • the attachment of the palladium compound through two sp 2 - hybridized nitrogen atoms improves the bonding strength compared e.g. to a bonding through carbon atoms, which is advantageous in terms of the reusability and recycleability of the catalyst system and reduces the risk of leaching of the palladium metal.
  • the sp 2 - hybridized nitrogen atoms to which the palladium is attached may be part of a heterocyclic ring comprising preferably between 5 and 10 ring atoms, preferably of form 5 to 6 ring atoms.
  • the ring may also comprise additional nitrogen or other heteroatoms like sulfur or oxygen.
  • the ring may also be substituted with substituents or condensed with carbocyclic or heterocyclic rings to form fused or condensed systems.
  • the two sp 2 -hybridized nitrogen system may be part of one ring system or
  • each sp 2 - hybridized nitrogen atom is part of a separate ring system.
  • Preferred ring systems comprising the sp 2 - hybridized nitrogen atoms are shown below: where A 1 , A 2 and A 3 may be the same or different and independently from each other selected from the group consisting of C, O, S or N.
  • a particularly preferred group of ligands are ligands comprising oxazoline ring systems with each sp 2 - hybridized nitrogen atom to which the palladium is bonded forming part of one oxazoline ring, which may optionally be substituted.
  • These ligands are generally referred to as bis- oxazoline or BOX ligands and have been described elsewhere in the literature, e.g. in Fraile et al., Coordination Chemistry Reviews 252 (2008), 624ff to which reference is made herewith for further details.
  • the respective products as well as their method of manufacture are known to the skilled man and the respective compounds are available from commercial sources.
  • R 1 to R 18 may be the same or different and may be selected from hydrogen, deuterium, methyl, ethyl, i-propyl, t-butyl .phenyl, benzyl, preferably benzyl, Phenyl, i-Propyl or t-Butyl and R 1 and R 2 may further represent indenyl rings.
  • the bis-oxazoline referred to above as Box is particularly preferred as part of the ligand used in the catalyst systems in accordance with the instant invention.
  • preferred ligands for use in the instant invention are molecules comprising an attachment position to the functional group FG2 of the modifying material, a spacer chain of at least 4 carbon atoms and a molecule part as depicted above comprising the two sp 2 - hybridized nitrogen atoms for the bonding of the palladium.
  • n is an integer in the range of from 3 to 9, preferably of from 4 to 7.
  • n is an integer in the range of from 3 to 9, preferably of from 4 to 7.
  • the palladium compound used in the catalyst systems in accordance with the instant invention can be any palladium compound comprising palladium which can be attached to the sp 2 - hybridized nitrogen atoms of the ligand.
  • the palladium compound can be provided as a salt, as an ionic or a non-ionic complex or in a pre-ligated form.
  • Preferred examples are Pd(OAc) 2 and PdCI 2 .
  • inorganic support materials a), modifying agents b), ligands and palladium compound it is apparent that the skilled man can chose amongst a wide variety of those components as long as the final product comprises a ligand with a spacer chain as defined hereinbefore having at least 4 carbon atoms between the atom bonded to the functional group FG2 and the place of attachment of the palladium compound and further provided that the ligand comprises at least two sp 2 - hybridized nitrogen atoms to which the palladium is attached.
  • Preferred catalysts comprise as component a) a mesoporous silica carrier, preferably MCM-41 , FSM-16 or particularly preferred SBA-15 which is modified by reaction with a modifying group preferably selected from silanes providing a SH- group for bonding to the ligand.
  • Preferred silanes are the mentioned mercaptopropyltrimethoxysilane [(CH 3 O) 3 Si(CH 2 ) 3 SH)], aminopropyltriethoxysilane [(C 2 H 5 O) 3 Si(CH 2 ) 3 NH 2 )], and
  • aminopropyltrimethoxysilane (CH 3 O) 3 Si(CH 2 ) 3 NH 2 )] of which the first is particularly preferred.
  • a particularly preferred ligand is
  • n 7
  • a process for the manufacture of this ligand is e.g.
  • an especially preferred catalyst system in accordance with the instant invention is the following:
  • Suitable solvents are water or organic solvents or mixtures thereof.
  • Suitable organic solvents include alcohols, ethers, glycols, ketones, aldehydes and nitriles and the like, of which solvents with a sufficient polarity to dissolve metal salts are generally preferred. Examples are water, methanol, ethanol, n-propanol, isopropyl alcohol, acetonitrile, acetone,
  • functionalizing agent can be removed by washing and/or drying, if appropriate.
  • the thus functionalized support can be subjected to calcinations to remove undesired materials.
  • modified support materials it is equally suitable to use commercially available modified support materials as long as the modified materials provide the necessary functional group FG2 for the attachment of the ligand.
  • modified materials provide the necessary functional group FG2 for the attachment of the ligand.
  • Those skilled in the art are familiar wth the many types of functionalized support materials which are available.
  • Suitable ligands are also available in many variants known to those skilled in the art.
  • the preferred 2,2'-(1-methyl-11-dodecenylidene) bis -(4,5 dihydrooxazole) can be obtained by a method as described and reviewed in G. Desimoni, G. Faita, K.A. J ⁇ rgensen, Chem. Rev. 106 (2006) 3561ff.
  • the immobilization of the ligand onto the modified surface can preferably be carried out in an analogous manner as described by Baleizao et al., J. Catal. 2004, 223, 106-113.
  • the active metal species can be provided in any form dissolvable in a solvent or carrier. It may be advantageous to use metal salts like chlorides or nitrates as they are typically more soluble than other metals but Pd(OAc) 2 is generally also suitable.
  • the metal loadings of the catalyst particles in accordance with the instant invention can vary depending on the intended use of the catalyst system. Generally, the metal loading is in the range of from O.001 to about 20 % by weight, preferably in the range of from 0.01 to 10 % by weight and especially preferred in the range of from 0.05 to 5 % by weight, based on the weight of the catalyst system.
  • the supported catalyst systems in accordance with the instant invention have unique and novel properties compared to known catalyst systems which make them particularly suitable for performing carbon-carbon couplings as well as for carbon-nitrogen couplings (like the so called Buchwald-Hartwig reaction) and for C-O couplings.
  • the use in the so-called Heck and Suzuki reactions is a particularly preferred application of the catalyst systems in accordance with the instant invention.
  • the Heck coupling reaction typically includes reacting an aryl or vinyl halide with an alkene in the presence of a palladium catalyst and a base.
  • the Suzuki coupling reaction typically includes reacting organoboron compounds, in particular aryl boronic acids with aryl halides. Both types of reactions are well known to the skilled man and have been described in the literature.
  • the Suzuki reaction is the most versatile method for the synthesis of biaryls due to the high stability, ease of preparation and low toxicity of the boronic acid compounds.
  • Biaryl sub-units which may be obtained through the Suzuki reaction include but are not limited to, a wide variety of natural and bioactive products like alkaloids, coumarins, flavonoids, lignans, polyketides, tannines, terpenes and peptides.
  • biphenyls are important pharmaceutical intermediates.
  • Typical products of the Buchwald-Hartwig reaction are arylpiperazines, which are important pharmaceutical intermediates.
  • Two examples for pharmaceutically active ingredients comprising the arylpiperazine structural element are
  • catalyst systems in accordance with the instant invention can be obtained in good yields, generally more than 75, preferably more than 80 and particularly preferred more than 90 % yield. Furthermore, the catalyst systems in accordance with the instant invention do not show a measurable leaching, i.e. the metal content in the final product after the reaction is below the limit of detectability.
  • heterogeneous catalyst systems can be easily separated (e.g. by simple filtration) from the desired product and the catalyst can be reused several times, i.e. more than five and preferably more than ten times without significant or measurable loss of catalytic activity.
  • a heterogeneous catalyst system was prepared using a commercially
  • SBA-15-SH surface modified mesoporous silica
  • SBA-15-SH surface modified mesoporous silica
  • the product was purchased from Aldrich chemicals under the catalogue reference number 538086.
  • the particle size of this product was 37-74 ⁇ m (200-400 mesh), the pore size was 6 nm (60 A) and the specific surface according to BET at 25 0 C was 500 m 2 /g.
  • reaction time was 24 hours and X was Methyl or Trifluoromethyl.
  • the catalyst system could be reused several times without a detectable loss of catalytic activity.
  • the yield after a reaction time of 24 h was 30 %.

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Abstract

Supported palladium containing catalyst systems comprising an inorganic support material, a modifying agent covalently attached to said inorganic support material through at least one first functional group FG1, such modifying agent comprising at least one second functional group FG2 for bonding a ligand thereto, a ligand covalently bound to said modifying group through said functional group FG2, and a palladium compound attached to said ligand wherein the ligand comprises a spacer group of at least 4 carbon atoms between the atom bonded to FG2 and the place of Pd attachment and Pd is attached via 2 sp2 -hybridized nitrogen atoms.

Description

Description
Non-leaching heterogeneous catalyst systems for coupling reactions
[0001] The present invention relates to non-leaching catalysts for C-C, C-O or
C-N couplings, the use thereof for such couplings and to a method for their manufacture.
[0002] Catalytic C-C. C-O or C-N couplings represent versatile methods for the preparation of a wide variety of different products, including intermediates and final products in the pharmaceutical area and other fields. Metal catalysts are generally used for these reactions and accordingly, metal catalyzed reactions have become part of the standard repertoire of the synthetic chemist. As an example, the so called Suzuki and Heck reactions are frequently carried out with palladium based catalyst systems. These two reactions are especially versatile one step methods for the preparation of complex structures as they can be found e.g. in
pharmaceutical products or a wide variety of natural and bioactive products like alkaloids, coumarins, flavonoids, lignans, polyketides, tannins, terpenes and peptides.
[0003] Despite the remarkable utility of metal catalysts for these reactions, there is one significant drawback in that they often remain in the organic product at the end of the reaction. This is in most cases, in particular in the pharmaceutical area not acceptable and requires expensive and time consuming additional steps to recover the catalyst metal. Metal content is closely regulated in many products, including also flavours, cosmetics, fragrances and agricultural chemicals.
[0004] The metal content problem is particularly imminent in cases where
homogenous catalysts are used. In these cases it is essential to remove the metal from the reaction solution in order to reuse the catalyst.
Furthermore, homogeneous catalyst systems are frequently composed of a metal/ligand system where these components are in a particular stoichiometric ratio with respect to one another. This makes the
purification of the product even more expensive.
[0005] Attempts to improve the reusability of metal catalyst systems by stabilizing the metal on a solid support have been undertaken. In those cases where the metal is not covalently bound to the support, the leaching of the metal, i.e. the dissolution of the metal in the reaction solution is a serious problem, as this leads to the issues discussed hereinbefore. In a significant number of cases it turned out that those "heterogeneous" catalysts were actually only a reservoir for highly active soluble forms of the metal, which were found in the reaction solution.
[0006] WO 2006/094392 discloses a catalyst comprising a functionalized silica gel material and a metal wherein the silica material is functionalized by co-condensation with a functionalizing agent, preferably selected from thiols or amines. 3-Mercaptopropyltrimethoxysilane is a preferred functionalizing agent.
[0007] WO 2006/121553 describes and claims a process for the manufacture of supported nanocatalysts wherein functionalizing agents for functionalizing the surface of a carrier material have at least two functional groups, one for the attachment to the surface of a carrier and the other functional group for attachment to the metal. According to this prior art process, the catalyst is prepared in two subsequent steps. In the first step, one of the functional groups of the functionalizing agent is attached to the carrier or support material and thereafter the catalytically active metal is attached to the remaining functional group of the functionalizing agent.
[0008] Fraile et al. (Coordination Chemistry Reviews 252 (2008) 624-646)
disclose experiments relating to the immobilization of chiral catalysts containing bis-oxazolines and related ligands. The catalytic metal is copper and the coordinative immobilization as well as the covalent attachment of the ligand to the support is described. The catalyst systems are useful in asymmetric catalysis in a variety of enantioselective reactions.
[0009] Richardson and Jones (Journal of Catalysis 251 (2007) 80-93) describe experimental results giving strong evidence of solution-phase catalysis associated with palladium leaching from immobilized thiols during Heck and Suzuki coupling of aryl iodides, bromides, and chlorides. Palladium acetate is immobilized on a 3- mercaptopropyl functionalized silica known as SBA-15 and the catalytic behaviour in various Heck and Suzuki couplings is analyzed. The data presented give strong evidence that in all cases the active catalyst species is a soluble species dissolved from the surface during the reaction and thus the catalytic mechanism overall appears to be a homogenous reaction and not the desired heterogeneous reaction. Since there is no catalytic activity without dissolved palladium species, the aforementioned issue of catalyst metal removal are also present in these systems.
[0010] Phan et al ( Tetrahedron 61 (2005) 12065-12073) disclose
polymer-supported palladium catalysed Suzuki-Miyaura reactions in batch and a mini-continuous flow reactor system. The thermal and mechanical stability of these polymer-supported catalysts is not satisfactory and the solubility of the support material in certain organic solvents is a further limitation on the usability.
[0011] WO -A 2007/102334 discloses polysilane or polysilane/inorganic material supported transition metal catalysts. According to the teaching of the reference a strong binding interaction between the catalyst metal and the support is considered disadvantageous compared to a metal supported only by adsorption or ionic binding as the former prevents the release of the metal. This clearly indicates that the active species of the catalyst is dissolved metal and thus all problems associated with homogenous catalyst outlined above also apply to the catalysts of this reference.
[0012] Hara et al. ( Chem.Commun., 2007, 4280-4282) describe the
functionalization of surfaces of elementary silicon with catalytically active Pd complexes and the application of these catalysts to the aerobic oxidation of benzylic alcohols. Elementary silicon is expensive and the surface properties thereof are not satisfactory for many purposes. C-C coupling reactions like the Suzuki coupling or Heck coupling are not mentioned as reactions which can be catalyzed.
[0013] EP -A 1186583 relates to a method for carrying out C-C coupling
reactions in the presence of supported palladium as a catalyst and a base in a monophase or multiphase solvent mixture. Palladium detaches itself from the support and is solubilized. After the reaction the palladium is redeposited on the carrier so that the amount of catalyst remaining in the product is low. Nevertheless, in particular for pharmaceutical purposes the residual palladium content in the solution is too high. Furthermore, the mechanism of detaching and redeposition is very sensitive to changes in the reaction conditions, which makes control of the reaction to achieve the desired low content of palladium in the reaction product difficult.
[0014] Yin and Liebscher (Chem. Rev. 2007, 107, 133-173) is related to
carbon-carbon coupling reactions catalyzed by heterogeneous palladium catalysts. In section 2.4. of this prior art reference Pd catalyst systems on modified silica are disclosed and the results of experiments with this type of catalysts are shown. Pd(II) on silica fixed by mercaptopropyl ligands using mercaptopropylsiloxane was prepared on mesoporous silica (Pd-SH-FSM) and on amorphous silica (Pd-SH-SiO2). The activity of the different recycled catalysts were in the order Pd-SH-FSM > Pd-SH-SiO2 > Pd deposited on nonfunctionalized mesoporous silica. Obviously the SH ligands prevent formation of less active Pd aggregates. Complexes of Formula I
[0015]
Figure imgf000005_0001
R is hydrogen or methyl were used for the coupling of aryl bromides and phenylboronic acid according to the general reaction scheme Il
Figure imgf000005_0002
(H) Yields of more than 60 % were achieved and the catalysts were
considered to be heterogeneous under the reaction conditions. However, the bonding of the Pd to an imino-nitrogen atom leads to undesired effects and reduces stability of the complex.
[0016] Another catalyst system for Suzuki C-C coupling reactions described by Yin and Liebscher is III
Figure imgf000006_0001
(III)
Again the bonding of the Pd through an imino nitrogen is disadvantageous.
[0017] Thus, there is still a need for heterogeneous catalytic systems useful in C-C, C-O or C-N couplings easily recoverable from the reaction mixture and good reusability without significant deterioration in catalytic
performance.
[0018] It was accordingly an object of the instant invention to provide novel
catalyst systems for the aforementioned reactions which are easily removable from the reaction medium and which can be repeatedly recycled and reused, thus leading to lower process costs and ecological benefits.
[0019] A further object of the invention was the use of the novel catalysts for C-C, C-O and C-N coupling reaction, in particular for so called Suzuki- and Heck-reactions.
[0020] These objects are achieved with the catalyst systems in accordance with claim 1 and with the use thereof in accordance with claim 15. Preferred embodiments of the invention are the subject of dependent claims and also described in more detail hereinafter. [0021] The catalyst systems in accordance with the instant invention show a very good catalytic activity in coupling reactions and the metal content in the product is extremely low, in many cases below the level of detectability.
[0022] The catalyst systems in accordance with the invention comprise as
component a) an inorganic support material. This support material can be selected from any inorganic material known to those skilled in the art for supporting catalyst particles, in particular catalyst particles comprising Pd as active metal. Suitable supports of this type include alumina, silica, silica gel, titania, kieselguhr, diatomaceous earth, bentonite, clay, zirconia, magnesia as well as oxides of other metals. Also suitable are porous solids, such as for example natural and synthetic zeolites or other materials which have ordered or quasi ordered pore structures. In those cases where porous solids are used it is preferred to use materials having a surface area according to BET of more than 20 m2/g, preferably of more than 50 m2/g.
[0023] Preferred inorganic support materials are silicates of the general formula RO4^Si - Aq, wherein q is an integer of from 0 to 4,
R is hydrogen or an organic group selected from:
straight chain or cyclic, substituted or unsubstituted C1 to C8, preferably C1 to C4 alkyl,
substituted or unsubstituted C4 - C10aryl or heteroaryl,
alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, alkylcarbonyl, alkoxycarbonyl, alkylthiocarbonyl, phosphonato, phosphinato, heterocyclyl and esters thereof, and
A is a hydrolyzable group selected from OR, halogen phosphate, phosphate ester, alkoxycarbonyl, hydroxyl, sulfate and sulfonato.
[0024] Preferred members of this group are tetraethoxysilane and silsesquioxane.
[0025] Another preferred group of inorganic silicates as support material are
siloxanes of the general formula (RO)3 -Si -R' - Si(OR)3 wherein R is as defined above and R' is a bridging group selected from alkylene or arylene, e.g. methylene, ethylene, propylene, ethenylene, phenylene, biphenylene or heterocyclyl. A preferred bridging group is 1 ,4-phenylene.
[0026] A particularly preferred group of inorganic materials is so called mesoporous silica. The most common types of these mesoporous nanoparticulate materials are MCM-41, FSM-16 and SBA-15. Mesoporous silica nanoparticles were first synthesized in 1990 by researchers in Japan (Yanagisawa et al., Bull.Chem.Soc.Japan., 63, 1990, pp 988ff) and later produced at Mobile Corporation (Beck et al., J.A.C.S. 114, 10834ff). WO 1992/06921 discloses synthesis and properties of a number of MCM materials suitable for the instant invention as inorganic support material.
[0027] Researchers at the University of Santa Barbara reported the manufacture of silica nanoparticles with larger pore sizes of from about 5 to 30 nm, which are since then referred to as SBA-materials. The larger surface of the SBA materials allows them to be filled with other materials.
[0028] Mesoporous silica nanoparticles are generally synthesized by reacting tetra ethyl orthosilicate with a template of micellar rods. The result is usually a collection of nano-sized spheres with a regular arrangement of pores. The template can then be removed by washing with a solvent. Respective procedures are described in the literature and known to the man skilled in the art.
[0029] MCM-41, FSM-16 and SBA-15 as two particularly preferred examples of this type are available from commercial sources.
[0030] The catalyst system comprises as component b) a modifying agent
providing the surface of the inorganic support material a) with a functional group suitable to attach a ligand thereto. To achieve this, the modifying group is covalently bonded to said inorganic support material through at least one first functional group FG 1 and provides at least one second functional group FG2 for bonding a ligand thereto.
[0031] Suitable modifying agents are compounds that include functional groups undergoing a reaction with bonding sites on the support material. The modifying agents include molecules having at least two functional groups, which can be the same or different. The at least one second functional group FG2 is selected to promote the bonding of a ligand thereto.
[0032] Modifying agents suitable for use in the instant invention include a variety of organic molecules as well as polymers and oligomers. Exemplary of suitable bifunctional agents are diacids such as oxalic acid, malonic acid, maleic acid, succinol acid and the like; dialcohols such as 1 ,2-ethane diol, 1 ,2-propanediol and 1 ,3-propandiol; hydroxyl acids such as glycolic acid, lactic acid and the like. Suitable polyfunctional compounds include sugars polyfunctional carboxylic acids and hydroxyl diacids.
[0033] Other suitable modifiying agents include ethanolamine, mercaptoethanol, 2-mercaptoacetate, amino acids, sulfonic acids, sulfobenzyl alcohol and other sulfobenzoyl compounds as well as in general compounds comprising amino and thiol functional groups.
[0034] Modifying agents can also be oligomers and polymers comprising a
plurality of functional groups. Examples of such oligomers or polymers are polyacrylates, polyvinylbenzoates, polyvinyl sulfate, polyvinylsulfonates or generally sulfonated polmers.
[0035] As a particularly suitable group of modifying agents b) for the modification of the preferred silicas as component a) compounds of the general formula X3^GeSi - R" -Y, wherein e is an integer between 0 and 2, X is a group capable of undergoing condensation, e.g. alkoxy or a group OG, halogen, allyl, phosphate, phosphate ester, alkoxycarbonyl, hydroxyl, sulfate and sulfonate,
G is an organic group, e.g. C1 - C2o— alkyl Or - C1 - C2o -alkenyl (in each case straight chain, branched, substituted or unsubstituted), aryl or heteroaryl (in each case substituted or unsubstituted) and
alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, alkylcarbonyl, alkoxycarbonyl, alkylthiocarbonyl, phosphonato,
phosphinato, heterocyclyc and esters thereof;
R" is selected from an aliphatic group -(CH2)b, wherein one or more of the hydrogen atoms on the methylene group may be substituted so that R" may be linear, branched, cyclic or unsaturated aliphatic or wherein R" is arylene, preferably 1 ,4-phenylene, and
Y is a functional group based on one of the following elements: S, N, O, C1 H, P1Si or halogen including , inter alia, SH, NH2, PO(OH)2, NHCSNH2, NHCONH2, SG, NHG1 PG3, PO(OG)2, NG2, imidazole, benzimidazole, thiazole, halogens and silanes.
[0036] Particularly preferred modifying agents b) are mercaptopropyltrimethoxysilane [(CH3O)3 Si(CH2)3SH)], aminopropyltriethoxysilane [(C2H5O)3 Si(CH2J3NH2)], and
aminopropyltrimethoxysilane [(CH3O)3 Si(CH2J3NH2)].
[0037] From the foregoing it is apparent that a combination of mesporous silica, in particular of MCM;-41 , FSM-16 or SBA-15 with a modifying agent of the general formula X3^GeSi - R" -Y as defined before is a preferred embodiment in accordance with the instant invention. Particularly prefereed is a combination of either MCM-41 , FSM-16 or SBA-15 as inorganic support material a) with either of mercaptopropyltrimethoxysilane [(CH3O)3 Si(CHz)3SH)], aminopropyltriethoxysilane [(C2H5O)3 Si(CH2J3NH2 )], and aminopropyltrimethoxysilane [(CH3O)3 Si(CH2J3NH2)] as modifying agent b).
[0038] In the catalyst systems according to the invention, a ligand is covalently bound to the at least one second functional group of the modifying agent which is available for ligand bonding, i.e. which is not involved in the attachment of the modifying agent to the inorganic support material. The ligand is covalently bound to the functional group rather than only attached through a coordinating bond. This improves the capability of the inventive catalyst systems to immobilize the palladium metal which is important relating to the work- up of the reaction product in reactions catalyzed with the inventive catalyst systems. In the course of the invention it has been found that it is important that the ligand comprises a spacer group of at least four (4), preferably at least five and particularly preferably at least 6 carbon atoms between the atom of the ligand bound to the functional group FG2 of the modifying agent b) and the place of attachment of the palladium compound. If the spacer group is shorter than four carbon atoms an interaction between the support material and the palladium metal may occur, which may have a detrimental influence on the catalytic
performance of the catalyst system. Furthermore, with shorter spacers, part or all of the palladium metal may undergo direct bonding of the palladium metal to the inorganic support, which may also be
disadvantageous. On the other hand, if the spacer provided by the ligand exceeds a certain number of carbon atoms, e.g. 7 to 9 carbon atoms, it may be beneficial to use a ligand where the rigidity of the spacer chain is enhanced by e.g. multiple bonds or substituents limiting the moveability of the spacer chain by steric hindering, e.g. voluminous substituents on the spacer chain forcing the ligand molecule into a fixed steric configuration.
[0039] Preferred spacer groups are alkylene groups -CH2— and the preferred chain length is between 6 and 15, preferably between 8 and 12 carbon atoms. The hydrogen atoms of the alkylene groups may be partly replaced by the aforementioned substituents providing a certain stereochemical configuration of the molecule. Without limiting the scope of those groups, condensed aryl or heteraryl or carbocyclyl or heterocyclyl substituents may be mentioned. Suitable substituents of this type are know to the skilled man so that there is no need for a detailed description herein.
[0040] At the end of the spacer group, the ligand to be used in the catalyst
systems according to the invention comprises at least two sp2 - hybridized nitrogen atoms to which the active catalyst metal, i.e. the palladium is attached. The attachment of the palladium compound through two sp2 - hybridized nitrogen atoms improves the bonding strength compared e.g. to a bonding through carbon atoms, which is advantageous in terms of the reusability and recycleability of the catalyst system and reduces the risk of leaching of the palladium metal.
[0041] The sp2- hybridized nitrogen atoms to which the palladium is attached may be part of a heterocyclic ring comprising preferably between 5 and 10 ring atoms, preferably of form 5 to 6 ring atoms. The ring may also comprise additional nitrogen or other heteroatoms like sulfur or oxygen. The ring may also be substituted with substituents or condensed with carbocyclic or heterocyclic rings to form fused or condensed systems. The two sp2 -hybridized nitrogen system may be part of one ring system or
alternatively, in accordance with a preferred embodiment, each sp2 - hybridized nitrogen atom is part of a separate ring system.
[0042] Preferred ring systems comprising the sp2 - hybridized nitrogen atoms are shown below:
Figure imgf000012_0001
where A1, A2 and A3 may be the same or different and independently from each other selected from the group consisting of C, O, S or N.
[0043] Among these ring systems, the following represent a particularly preferred group
Figure imgf000012_0002
C-9 C-10 C-11 C-12
Figure imgf000012_0003
C-13 C-14 C-15
[0044] A particularly preferred group of ligands are ligands comprising oxazoline ring systems with each sp2 - hybridized nitrogen atom to which the palladium is bonded forming part of one oxazoline ring, which may optionally be substituted. These ligands are generally referred to as bis- oxazoline or BOX ligands and have been described elsewhere in the literature, e.g. in Fraile et al., Coordination Chemistry Reviews 252 (2008), 624ff to which reference is made herewith for further details. The respective products as well as their method of manufacture are known to the skilled man and the respective compounds are available from commercial sources.
[0045] The following are particularly preferred bis-oxazoline ligands for use in the catalyst systems in accordance with the instant invention:
Figure imgf000013_0001
Box azaBox
Figure imgf000013_0002
Pybox Pyox
Ji6 ,15
Figure imgf000013_0003
Quinox
wherein R1 to R18 may be the same or different and may be selected from hydrogen, deuterium, methyl, ethyl, i-propyl, t-butyl .phenyl, benzyl, preferably benzyl, Phenyl, i-Propyl or t-Butyl and R1 and R2 may further represent indenyl rings.
[0046] The bis-oxazoline referred to above as Box is particularly preferred as part of the ligand used in the catalyst systems in accordance with the instant invention.
[0047] From the foregoing it becomes apparent that preferred ligands for use in the instant invention are molecules comprising an attachment position to the functional group FG2 of the modifying material, a spacer chain of at least 4 carbon atoms and a molecule part as depicted above comprising the two sp2- hybridized nitrogen atoms for the bonding of the palladium.
[0048] The following shows an exemplary structure of a suitable ligand using the box structure as depicted above and a bonding site to the functional group FG2 of the modifying agent comprising a double bond;
wherein n is an integer in the range of from 3 to 9, preferably of from 4 to 7. As is apparent for the skilled man, other preferred ligands for use in the instant invention and comprising the other preferred oxazoline groups as depicted above or comprising the ring systems shown above can be obtained in a similar manner. The man skilled in the art is aware how to synthesize the respective ligands and thus more detailed explanations are not necessary here.
[0049] The palladium compound used in the catalyst systems in accordance with the instant invention can be any palladium compound comprising palladium which can be attached to the sp2- hybridized nitrogen atoms of the ligand. The palladium compound can be provided as a salt, as an ionic or a non-ionic complex or in a pre-ligated form. Preferred examples are Pd(OAc)2 and PdCI2. [0050] Summarizing the foregoing detailed description of inorganic support materials a), modifying agents b), ligands and palladium compound it is apparent that the skilled man can chose amongst a wide variety of those components as long as the final product comprises a ligand with a spacer chain as defined hereinbefore having at least 4 carbon atoms between the atom bonded to the functional group FG2 and the place of attachment of the palladium compound and further provided that the ligand comprises at least two sp2- hybridized nitrogen atoms to which the palladium is attached.
[0051] Preferred catalysts comprise as component a) a mesoporous silica carrier, preferably MCM-41 , FSM-16 or particularly preferred SBA-15 which is modified by reaction with a modifying group preferably selected from silanes providing a SH- group for bonding to the ligand. Preferred silanes are the mentioned mercaptopropyltrimethoxysilane [(CH3O)3 Si(CH2)3SH)], aminopropyltriethoxysilane [(C2H5O)3 Si(CH2)3NH2)], and
aminopropyltrimethoxysilane [(CH3O)3 Si(CH2)3NH2)], of which the first is particularly preferred. A particularly preferred ligand is
2,2'-(1-methyl-11-dodecenylidene)bis -(4,5 dihydrooxazole) as depicted in the general structure
Figure imgf000015_0001
wherein n is 7. A process for the manufacture of this ligand is e.g.
disclosed in Hara et al. (Chem. Commun., 2007, 4280-4282, supplemental information).
[0052] Thus, an example of an especially preferred catalyst system in accordance with the instant invention is the following:
Figure imgf000016_0001
[SiO]x
which can be obtained for example by modifying a mesoporous silica, preferably of the type SBA-15, with mercaptopropyltrimethoxysilane and thereafter attaching 2,2'-(1-methyl-11-dodecenylidene)bis -(4,5 dihydrooxazole) (as shown above) as ligand and finally using palladium diacetate as active metal compound.
[0053] The following detailed description of the manufacture of a catalyst system according to the instant invention is an exemplary description how the catalyst systems in accordance with the instant invention can be synthesized. The skilled man knows how to choose the specific reaction conditions to adopt same to the specific components used.
[0054] In a first step, the inorganic support material and the modifying agent are reacted, typically in the presence of a solvent or a carrier. Suitable solvents are water or organic solvents or mixtures thereof. Suitable organic solvents include alcohols, ethers, glycols, ketones, aldehydes and nitriles and the like, of which solvents with a sufficient polarity to dissolve metal salts are generally preferred. Examples are water, methanol, ethanol, n-propanol, isopropyl alcohol, acetonitrile, acetone,
tetrahydrofurane, ethylene glycol, dimethylformamide, dimethylsulfoxide and methylene chloride.
[0055] After reacting the support and modifying agent, solvent and/or excess
functionalizing agent can be removed by washing and/or drying, if appropriate. The thus functionalized support can be subjected to calcinations to remove undesired materials.
[0056] Instead of manufacturing the modified support material as described
above, it is equally suitable to use commercially available modified support materials as long as the modified materials provide the necessary functional group FG2 for the attachment of the ligand. Those skilled in the art are familiar wth the many types of functionalized support materials which are available.
[0057] Suitable ligands are also available in many variants known to those skilled in the art. The preferred 2,2'-(1-methyl-11-dodecenylidene) bis -(4,5 dihydrooxazole) can be obtained by a method as described and reviewed in G. Desimoni, G. Faita, K.A. Jørgensen, Chem. Rev. 106 (2006) 3561ff.
[0058] The immobilization of the ligand onto the modified surface can preferably be carried out in an analogous manner as described by Baleizao et al., J. Catal. 2004, 223, 106-113.
[0059] The complexing of the active metal species (the Pd compound) is
described in the literature and the skilled man knows how to perform this step. The active metal species can be provided in any form dissolvable in a solvent or carrier. It may be advantageous to use metal salts like chlorides or nitrates as they are typically more soluble than other metals but Pd(OAc)2 is generally also suitable.
[0060] It has proven advantageous if the modifying agent is reacted with the
ligand first before the active catalyst metal species is brought into the system. It is believed that the reason for this advantage resides in the fact that when using a ligand already comprising the active metal species part of the active metal may also react with the functionalized support and the resulting species is no longer catalytically active. SBA-15 modified with mercaptopropyltrimethoxysilane is known as a good palladium scavenger as has been shown by various research groups.
[0061] The metal loadings of the catalyst particles in accordance with the instant invention can vary depending on the intended use of the catalyst system. Generally, the metal loading is in the range of from O.001 to about 20 % by weight, preferably in the range of from 0.01 to 10 % by weight and especially preferred in the range of from 0.05 to 5 % by weight, based on the weight of the catalyst system.
[0062] The catalyst systems in accordance with the instant invention can in
general have an average diameter (weight average diameter) of 100 nm to 1000 μm, preferably of from 1 μm to 100 μm and particularly preferred of 30 μm to 80 μm .
[0063] The supported catalyst systems in accordance with the instant invention have unique and novel properties compared to known catalyst systems which make them particularly suitable for performing carbon-carbon couplings as well as for carbon-nitrogen couplings (like the so called Buchwald-Hartwig reaction) and for C-O couplings. The use in the so-called Heck and Suzuki reactions is a particularly preferred application of the catalyst systems in accordance with the instant invention.
[0064] The Heck coupling reaction typically includes reacting an aryl or vinyl halide with an alkene in the presence of a palladium catalyst and a base. The Suzuki coupling reaction typically includes reacting organoboron compounds, in particular aryl boronic acids with aryl halides. Both types of reactions are well known to the skilled man and have been described in the literature. The Suzuki reaction is the most versatile method for the synthesis of biaryls due to the high stability, ease of preparation and low toxicity of the boronic acid compounds. Biaryl sub-units which may be obtained through the Suzuki reaction include but are not limited to, a wide variety of natural and bioactive products like alkaloids, coumarins, flavonoids, lignans, polyketides, tannines, terpenes and peptides. In particular biphenyls are important pharmaceutical intermediates.
[0065] Typical products of the Buchwald-Hartwig reaction are arylpiperazines, which are important pharmaceutical intermediates. Two examples for pharmaceutically active ingredients comprising the arylpiperazine structural element are
Figure imgf000019_0001
common name ciprofloaxin
(antibacterial)
and
Figure imgf000019_0002
common name aripiprazole
(neuroleptic) With the catalyst systems in accordance with the instant invention, these compounds can be obtained in good yields, generally more than 75, preferably more than 80 and particularly preferred more than 90 % yield. Furthermore, the catalyst systems in accordance with the instant invention do not show a measurable leaching, i.e. the metal content in the final product after the reaction is below the limit of detectability. The
heterogeneous catalyst systems can be easily separated (e.g. by simple filtration) from the desired product and the catalyst can be reused several times, i.e. more than five and preferably more than ten times without significant or measurable loss of catalytic activity. [0067] The following examples demonstrate preferred embodiments of the instant invention and of the catalyst systems described more generally before.
[0068] Examples
[0069] Example 1
[0070] A heterogeneous catalyst system was prepared using a commercially
available surface modified mesoporous silica know as SBA-15-SH which had been surface modified with mercaptopropyltrimethoxysilane and which had a functional SH-group content of approximately 1.2 mmol/g of material. The product was purchased from Aldrich chemicals under the catalogue reference number 538086. The particle size of this product was 37-74 μm (200-400 mesh), the pore size was 6 nm (60 A) and the specific surface according to BET at 25 0C was 500 m2/g.
2,2'-(1-methyl-11-dodecenylidene)bis -(4,5 dihydrooxazole) was immobilized on this material using methylene dichloride as solvent and azo-iso-butyro nitrile (AIBN) as initiator in an analogous manner as described in Baleizao et al., J. Catal. 2004, 223, 106-113. Palladium diacetate was added to obtain the final heterogeneous catalyst system comprising Pd bound to two sp2 - hybridized nitrogen atoms of the oxazole rings and being separated from the surface of the support material by a spacer of 11 carbon atoms. The structure of the catalyst system may be depicted as follows:
Figure imgf000021_0001
[SiO]x
[0071] Example 2
[0072] The catalyst system obtained in accordance with Example 1 was used for a Suzuki cross coupling reaction according to the following reaction scheme:
Figure imgf000021_0002
The reaction time was 24 hours and X was Methyl or Trifluoromethyl.
[0073] When X was methyl, the desired product was obtained in 94 % yield; when
X was trifluoromethyl, the yield was 87.5 %.
[0074] To determine any potential leaching two samples of different reactions were analyzed by ICP/OES (Varian, Vista-MPX, CCD-simultaneous ICP-OES, Pd-standard 10 000 ppm, Pd in % 5 HNO3. In both samples no palladium could be detected, i.e. the palladium content, if any, was below the limit of detection of the method.
[0075] The catalyst system could be reused several times without a detectable loss of catalytic activity.
[0076] Example 3
[0077] The catalyst system obtained in accordance with Example 1 was used for a Buchwald-Hartwig reaction as follows:
Figure imgf000022_0001
NaO-t-Bu
The yield after a reaction time of 24 h was 30 %.
[0078] Example 4 - Comparative homogenous catalyst
[0079] For comparison purposes a homogenous catalyst system using the same ligand and the same Pd source, but without a support material was tested under the same reaction conditions with the same substrates. With both substrates the yields of the desired product after a reaction time of 24 hours and the same reaction conditions were approximately thirty percent and 25 % , respectively, i.e. significantly lower than with the catalyst systems in accordance with the instant invention.

Claims

Claims
1. A supported palladium containing catalyst system comprising
a) an inorganic support material.b) a modifying agent covalently attached to said inorganic support material through at least one first functional group FG 1 , such modifying agent comprising at least one second functional group FG2 for bonding a ligand thereto.c) a ligand covalently bound to said modifying agent through said functional group FG2, andd) a palladium compound attached to said ligand, whereine) said ligand comprises a spacer group of at least four (4) carbon atoms between the atom bonded to the functional group FG2 and the place of attachment of said palladium compound, andf) said palladium compound is attached to said ligand via two sp2-hybridized nitrogen atoms.
2. A supported catalyst system in accordance with claim 1 wherein the inorganic support material is selected from alumina, silica, silica gel, titania, kieselguhr, diatomaceous earth, bentonite, clay, zirconia, magnesia or oxides of other metals, natural and synthetic zeolites or mesoporous silica.
3. A supported catalyst system in accordance with any of claims 1 or 2 wherein the inorganic support material has a BET surface area at 25 0C as determined according to the BET method, of at least 20 m2/g.
4. A supported catalyst system in accordance with any of claims 1 to 3 wherein the inorganic support material is one of mesoporous silica products MCM-41, FSM-16 or SBA-15.
5. A supported catalyst system in accordance with any of claims 1 to 4 wherein the modifying agent is selected from the group consisting of oxalic acid, malonic acid, maleic acid, succinol acid, 1 ,2-ethane diol, 1 ,2-propanediol and 1 ,3-propandiol, glycolic acid, lactic acid, sugar polyfunctional carboxylic acids and hydroxyl diacids, ethanolamine, mercaptoethanol, 2-mercaptoacetate, amino acids, sulfonic acids, sulfobenzyl alcohol and other sulfobenzoyl compounds, compounds comprising amino and thiol functional groups, and oligomers and polymers comprising a plurality of functional groups.
6. A supported catalyst system in accordance with any of claims 1 to 5 wherein the modifying agent b) is selected from compounds of the general formula X3^G6Si - R" -Y, wherein e is an integer between 0 and 2, X is a group capable of undergoing condensation, G is an organic group, R" is selected from an aliphatic group -(CH2).,, wherein one or more of the hydrogen atoms on the methylene group may be substituted so that R" may be linear, branched, cyclic or unsaturated aliphatic or wherein R" is arylene, and Y is a functional group based on one of the elements S1N1O1C1H1P1Si or halogen.
7. A supported catalyst system in accordance with claim 6 wherein X is selected from the group consisting of alkoxy groups, groups OG1 halogen, allyl, phosphate, phosphate ester, alkoxycarbonyl, hydroxyl, sulfate and sulfonato.
8. A supported catalyst system in accordance with any of claims 6 or 7 wherein G is selected from C1 - C20 -alkyl or C1 - C20 -alkenyl (in each case straight chain, branched, substituted or unsubstituted), aryl or heteroaryl (in each case substituted or unsubstituted) and alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, alkylcarbonyl, alkoxycarbonyl, alkylthiocarbonyl, phosphonato, phosphinato, heterocyclyl and esters thereof.
9. A supported catalyst system in accordance with any of claims 6 to 8 wherein R" is selected from an aliphatic group -(CH2)b wherein one or more of the hydrogen atoms on the methylene group may be substituted so that R" may be linear, branched, cyclic or unsaturated aliphatic or wherein R" is arylene.
10. A supported catalyst system in accordance with any one of claims 6 to 9
wherein Y is selected from SH, NH2, PO(OH)2, NHCSNH2, NHCONH2, SG, NHG, PG3, PO(OG)2, NG2, imidazole, benzimidazole, thiazole, silanes and halogens.
11. A supported catalyst system in accordance with any of claims 6 to 10 wherein the modifying agent is selected from mercaptopropyltrimethoxysilane [(CH3O)3 Si(CH2J3SH)], aminopropyltriethoxysilane [(C2H5O)3 Si(CH2J3NH2)], and aminopropyltrimethoxysilane [(CH3O)3 Si(CH2)3NH2)].
12. A supported catalyst system in accordance with any of claims 1 to 11 wherein the sp2-hybridized nitrogen atoms in the ligand are contained within ring systems of the formula
Figure imgf000024_0001
wherein A1, A2 and A3 may be the same or different and independently from each other selected from the group consisting of C, O, S or N.
13. A supported catalyst system in accordance with any of claims 1 to 12 wherein the ligand is selected from the group consisting of
Figure imgf000025_0001
Box azaBox
Figure imgf000025_0002
Pybox Pyox
Figure imgf000025_0003
Quinox wherein R1 to R18 may be the same or different and may be selected from H, D, methyl, ethyl, i-propyl, t-butyl,phenyl, or benzyl and R1 and R2 may further represent indenyl rings.
14. A supported catalyst system in accordance with any of claims 1 to 13 having the formula
Pd(OAc)2
Figure imgf000026_0001
[SiO]x
15. Use of the supported catalyst systems in accordance with any of claims 1 to 14 for the catalysis of carbon-carbon, carbon-nitrogen or carbon-oxygen couplings.
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