Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/38—Polysiloxanes modified by chemical after-treatment
  • C08G77/382—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon
  • C08G77/398—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon containing boron or metal atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/21—Cyclic compounds having at least one ring containing silicon, but no carbon in the ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/38—Polysiloxanes modified by chemical after-treatment
  • C08G77/382—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon
  • C08G77/388—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon containing nitrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/38—Polysiloxanes modified by chemical after-treatment
  • C08G77/382—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon
  • C08G77/395—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon containing phosphorus

Definitions

• the invention relates to polyhedral oligomeric silsesquioxane (POSS)-linked ligands and their salts, synthesis of said polyhedral oligomeric silsesquioxane (POSS)-linked ligands and their application in transition metal catalyzed cross-coupling reactions exemplified by Palladium-based catalyst systems.
• PES polyhedral oligomeric silsesquioxane
• Palladium catalysts bearing an N-heterocyclic carbene and sterically demanding phosphine ligands display the most robust and active catalytic systems to date (review on Pd-complexes of N-heterocyclic carbenes for cross-coupling reactions: M. G. Organ et al. Angew. Chem. Int. Ed. 2007, Vol 46, 16, 2768-2813, recent examples of applications of phosphine ligands: M. Beller, Adv. Synth. Catal. 2008, 350, 2437- 2442, M. Beller, Chem.-Eur. J. 2008,14, 3645-3652; S. L. Buchwald Acc. Chem. Res. 2008, Vol. 41 , 1 1 , 1461 -1473 and references cited therein).
• the application of homogeneous transition metal catalysts can result in soluble metal contamination. These soluble metals can be detrimental to product quality and product yield.
• the metal catalyst In the case of active pharmaceutical ingredient (API) development, the metal catalyst must be removed to a regulated level. This can be achieved by e.g. chemical metal scavenging substances or techniques where the metal residues are removed by physical methods such as extraction, distillation or precipitation.
• the POSS linked ligands according to the invention thus do not necessarily have to be monodentate. They could also be used as bidentate or tridentate ligands which are connected by linker molecules e.g. alkyl chains.
• the POSS linked ligands in a bidentate or tridentate molecule can be identical or different from each other.
• the invention also encompasses the salts of the POSS linked ligands.
• Said salts are obtained by the simple reaction of a leaving group containing POSS-connected alkyl residue with the corresponding ligand.
• the leaving group may e.g. be halogen, sulfonate, triflate, acetate or phosphate.
• R 1a , R 1b ,R 1c is each independently selected from the group consisting of same or different branched or linear C1-C20 alkyl chains, cyclo alkyl, C1-C20 alkoxy, aryl, aryloxy, heteroaryl and arylalkyl groups,
• k, I, m is 0 or 1 provided that k+l+m > 1 ,
• R 2a , R 2b , R 2c is a spacer that binds the polyhedral oligomeric silsesquioxane (POSS) to the ligand L,
• RR 22aa ,, RR 22bb ,, RR 22cc iiss each independently selected from the group consisting of linear or branched C1-C20 alkyl, C3-C10 cyclic alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkenyloxy, aryloxy, C1-C20 alkylthio, C1-C20 carboxylate, aryl or heteroaryl, C1-C20 alkyl halogenide, annulated aryl or heteroaryl, C3-C10 cyclic alkyl groups which in turn may each be further substituted with one or more groups selected from hetero atom or aryl groups, ether, polyether polythioether, amino, aryl bridged alkyl chain where the aryl moiety can include further substitution pattern and
• ligand L is an uncharged electron donor, whereas in structures II and IV L + is a protonated species of L,
• H is hydrogen
• Q is a branched or linear substituted or unsubstituted alkyl chain with a chain length ranging from Ci to C2o- Furthermore Q may be a unsubstituted or substituted cyclic alkyl, aryl or heteroaryl group where the aryl and heteroaryl moieties can include further substitution pattern.
• X " is a mono- or polyvalent organic or inorganic anion
• polyhedral oligomeric silsesquioxanes as used herein means that the POSS molecule can be regarded in a simplified manner as a roughly 3- dimensional geometric structure with flat faces and straight edges in which the Si- atoms are located at the corners of the structure.
• the POSS molecule is a pentahedral structure in the shape of a triangular prism with 6 Si atoms located at the corners of the structure.
• the POSS molecule is a hexahedral structure in the shape of a cube with 8 Si atoms located at the corners of the structure.
• substituents R in the structure shown above and in the following structures are not all identical.
• One substituent R is needed as spacer that binds the POSS molecule to the ligand L, i.e. one of the substituents R equals substituent R 2 .
• the POSS molecule is a heptahedral structure in the shape of a pentagonal prism with 10 Si atoms located at the corners of the structure.
• POSS molecules are known to the skilled artisan since the first synthesis by Lichtenhan et al. in 1995 (J. D. Lichtenhan Comments. Inorg. Chem. 1995, Vol. 17, No. 2, pp.1 15-130; A. M. Seifalian, Acc. Chem. Res. 2005, Vol 38, No. 1 1 879-884).
• the POSS molecules which are also referred to as POSS-cages display rigid and robust structures due to the strong framework resulting from their shorter bond.
• the spacer R 2a , R 2b , R 2c bonds to the polyhedral oligomeric silsesquioxanes (POSS) molecule over a Si or O atom of the POSS molecule.
• the spacer R 2a , R 2b , R 2c can bond to the ligand L via all bonds that are known to the skilled artisan preferably via C, O, N or S :
• polyhedral oligomeric silsesquioxanes (POSS) molecules with the generic formula ((R 1 )n-i(SiOi, 5 )n R 2 ) can be bonded to ligands and thus be used for enlarging the catalyst structure in order to enable membrane filtration separation.
• R 1 , R 2 is a generic term that also includes the a, b, c species as previously defined .
• One d rawback of m ass d ependent m em bran e-filtration methodology is that a certain mass difference between the used catalyst and the substrates (and products) is required, so that retention of the catalyst is possible while product is transported through the membrane.
• most filtration techniques are limited to small sized molecules with a much lower molecular mass than the catalyst, since commercially used catalysts are of molecular weight between 400 and 900 g/mol.
• POSS-enlarged ligands for homogeneous catalyst systems are presented in this invention. These catalysts preferably have molecular weights ranging from 1500 to 3000 g/mol. Due to the increased mass of the catalyst a mass difference between catalyst and product can be reached that is sufficient to separate catalyst and product by membrane filtration. Products of a much larger weight range can thus be separated from a homogeneous catalyst comprising POSS enlarged ligands. The increased mass allows retention of the catalyst, passage of the product and final isolation of larger molecules by filtration . With respect to the production processes of intermediates and final products for the pharmaceutical industry, these new catalyst systems are of high-interest.
• ligands are chemical compounds comprising one or several atoms.
• a coordinate bond is formed when one or several atoms of a ligand contribute their electrons or their orbitals filled with electrons to another atom.
• the ligand contributing the electrons is designated as the "donor” whereas the atom accepting the free electrons or the electrons from a filled orbital of the donor is designated as the "acceptor”.
• Ligand-atoms contributing the electrons or orbitals for the coordinate bonds usually, are main-group-elements from groups lll-VII with low oxidation numbers (e.g. C, N) Acceptors on the other hand, typically, are metal atoms with high oxidation numbers, e.g. z. B.
• An uncharged donor thus, is a ligand without net-charge that contributes electrons or orbitals filled with electrons for a coordinate bond with an acceptor.
• Examples of uncharged donors are (wherein the two dots preceeding the letter depict the electrons participating in the coordinate bond):
• carbon too can act as an uncharged (electron) donor.
• electron Usually found as carbene, the carbon atom bears a pair of electrons in an orbital. These electrons are provided for an uncharged sigma bond with the metal center. This is usually expressed by structures drawn as:
• Charged (electron) donors on the other hand carry a net-charge, i.e. cationic donors bear a positive net-charge and anionic donors bear a negative net-charge.
• the polyhedral oligomeric silsesquioxane (POSS)-linked ligands and their salts according to the invention can be considered as "nanoparticles or nanocomposites" due to the fact that their size ranges several nanometers.
• the POSS linked ligands and their salts according to the present invention are on the one hand soluble which is a precondition for their use in homogeneous catalysis and on the other hand filtratable by membrane filtration methods which is a precondition for their cost efficient and simple removal out of a reaction solution.
• the use of POSS linked ligands or their salts for homogeneous transition metal catalysts therefore combine in an unexpected manner the
• the POSS linked ligands in particular their salts have another advantage over ligands or their salts that are not linked to a POSS molecule.
• Ligand salts having very low solubility in common organic solvents e.g. toluene show significantly improved solubility when they are linked to a POSS molecule.
• POSS enlarged salts thereof show drastically enhanced solubilities. The enhanced solubility will greatly facilitate the construction of the transition metal catalysts with these ligand salts in terms of ease of reaction performance. Tests showed that in toluene, which is widely used as solvent in commercial applications, POSS-free imidazolium and phosphonium salts are unsoluble whereas the POSS-derivatives can be dissolved very well.
• the present invention also pertains the application of novel nanoparticle linked phosphine and N-heterocyclic carbene ligands in cross-coupling reactions, where nanometer sized polysilsesquioxane cubes or other polyhedral shapes as mentioned above serve as nano-anchors.
• Preferred substituents R 1a , R 1 b ,R 1c of the polyhedral oligomeric silsesquioxanes (POSS) linked ligands according to the invention are unsubstituted branched alkyl chains. These substituents ensure solubility of the POSS architecture in various organic polar and non-polar solvents. It is thus important that the preferred
• substituents R 1a"c bear no functional groups such as e.g. OH, NH or COOH.
• the spacer molecules R 2a , R 2b , R 2c are linear Ci-C2o alkyl, more preferably linear C3-Cio alkyl.
• polyhedral oligomeric silsesquioxanes (POSS) ligands are of the general formula (II)
• the ligand L is preferably selected from the group consisting of N-heterocyclic carbene, amine, imine, phosphine, stibine, arsine, carbonyl compound, carboxyl compound, nitrile, alcohol, ether, thiol or thioether.
• ligand L of the polyhedral oligomeric silsesquioxanes (POSS) ligand according to the invention is a N-heterocyclic carbene.
• N-heterocyclic carbenes are extremely reactive intermediates that are very difficult to isolate. Further, many substances destroy the N-heterocyclic carbenes through chemical interaction. It is thus surprising that it is possible to link the oligomeric silsesquioxanes (POSS) molecules with a N-heterocyclic carbene ligand.
• the polyhedral oligonneric silsesquioxanes (POSS) linked N- heterocyclic carbenes or their salts are of the following structures:
• polyhedral oligomeric silsesquioxanes (POSS) linked triazole-carbenes or their salts that are of the following structures:
• R 1 is the same or different branched or linear C1-C20 alkyi chains, cyclo alkyi, C1-C20 alkoxy, aryl, aryloxy, arylalkyi groups, substitution pattern also includes further POSS fragments having the same or different structure.
• R 1 may also be multiply substituted halogen alkyi, unsubstituted or substituted aryl groups and substituted alkyi groups, aryloxy, hetaryloxy groups.
• X " is a mono or polyvalent organic or inorganic anion.
• the spacer molecule R 2 that binds the POSS-molecule and to the N-atom of the N- heterocyclic carbene is selected from the group consisting of C1-C20 linear or branched alkyi chain, ether, polyether polythioether, amino, aryl bridged alkyi chain where the aryl moiety can include further substitution pattern, C3-C10 cyclic alkyi, Ci- C20 alkoxy, C2-C20 alkenyl, C2-C20 alkenyloxy, aryloxy, C1-C20 alkylthio, C1-C20 carboxylate, aryl or heteroaryl, C1-C20 alkyi halogenide, annulated aryl or heteroaryl, C3-C10 cyclic alkyi groups which in turn may each be further substituted with one or more groups selected from hetero atom or aryl groups.
• alkyi chain can contain further complexing moieties like phosphine derivatives.
• R 3 , R 4 , R 5 and R 6 are the same or independent from each other and selected from the group consisting of hydrogen, linear or branched C1-C20 alkyi, C3-C10 cyclic alkyi, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkenyloxy, aryloxy, C1-C20 alkylthio, C1-C20 carboxylate, aryl or heteroaryl, multiply substituted halogen aryl or heteroaryl, Ci- C20 alkyi halogenide, multiply substituted halogen alkyi, annulated aryl or heteroaryl, C3-C10 cyclic alkyi groups which in turn may each be further substituted with one or more groups selected from hetero atom or aryl groups.
• R 5 or R 6 may also depict a POSS-molecule with the structure (R 1 ) n - i(SiOi, 5 )n linked by a spacer molecule R 2 to a carbon atom of the N-heterocyclic carbenes or their salts of the above given structures.
• N-heterocyclic carbene contains an additional C1-C20 alkyi chain- bridged POSS-moiety leading to a N-heterocyclic carbene ligand with two POSS molecules of the structure as depicted in formula VII and Vila:
• POSS linked N-heterocyclic carbene may be connected via an alkyi chain R 7 to another POSS linked N-heterocyclic carbene, e.g. POSS linked imidazole thus leading to a dimeric structure as depicted in formula VIII and Villa:
• R 7 is substituted or unsubstituted linear or branched C1-C10 alkyi chain.
• any of the ligands substituents R 3 -R 6 may further include one or more functional groups.
• suitable functional groups include but are not limited to: hydroxyl, amine, amide, nitrile, thiol, thioether, ketone, aldehyde, ester, ether, imine, nitro, carboxylic acid, disulfide, carbonate and halogen.
• Unsymmetrical substituted N-heterocyclic carbenes and the corresponding salts thereof contain one C1-C20 alkyl chain-bridged POSS-moiety on one N-atom and a 2,4,6-trimethylbenzene (mesityl) substituent on the other N-atom of the imidazole moiety (formulas IX and IXa) .
• ligand L is a phosphine or a salt thereof.
• the phosphine-based ligands or their salts disclosed in this present patent are preferably of general formula: (R itSiOLs) ',n )n-i(Si0 1 i5 ) ',n
• R 1 is the same or different branched or linear C1-C20 alkyl chains, cyclo alkyl, C1-C20 alkoxy, aryl, aryloxy, arylalkyl groups, substitution pattern also includes further POSS fragments having the same or different structure.
• R 1 may also be multiply substituted halogen alkyl, unsubstituted or substituted aryl groups and substituted alkyl groups, aryloxy, hetaryloxy groups.
• X " is a mono- or polyvalent organic or halide anionic ion.
• R 8 and R 9 are the same or different branched or linear C1-C20 alkyl chains, cyclo alkyl, C1-C20 alkoxy, aryl, aryloxy, arylalkyl groups.
• R 8 and R 9 are adamantyl radicals XI or XIa where the phosphorus atom in XI is bound at the 2-postion and in XIa at the 1 -position.
• the spacer R 2 between the POSS-molecule and the attached phosphorus is selected from the group consisting of C1-C20 linear or branched alkyl chain, ether, polyether polythioether, amino, aryl bridged alkyl chain where the aryl moiety can include further substitution pattern.
• R 2 , R 8 and R 9 contain aryl groups, where the aryl groups are bonded to the P-atom and the POSS moieties is attached via alkyl chains R 10 that are connected to the said aryl groups as depicted in formula XII.
• Alkyl chain R 10 connected to the aryl group thus corresponds to spacer R 2 .
• R 10 is the same or different branched or linear C 1 -C 2 0 alkyl chains, cyclo alkyl, C 1 -C 2 0 alkoxy, aryl, aryloxy, arylalkyi groups, substitution pattern also includes further POSS fragments having the same or different structure.
• R 10 may also be multiply substituted halogen alkyl, unsubstituted or substituted aryl groups and substituted alkyl groups, aryloxy, hetaryloxy groups.
• alkyl chain can contain further complexing moieties like imidazol derivatives (formula XII):
• the POSS linked ligands according to the present invention can be considered as being nanoparticle anchored ligands. They can be used in metal catalyzed reactions in combination with nanofiltration technology.
• the nanometer- sized POSS-molecule to which the catalyst is linked allows specific filtration of the reaction products and other components where the nano-anchored catalyst remains within the membrane sphere.
• high molecular weights of these ligands lead to the corresponding transition metal catalysts with molecular weights ranging from 1 500 to 3000, which allows synthesis and filtration of larger sized molecules.
• transition metal complexes with different POSS linked ligands are given below:
• the corresponding transition metal complexes preferably palladium complexes can be obtained and used in cross-coupling reactions in two ways: 1 . they can be isolated after reaction of the phosphonium or imidazolium salts with bases and subsequent addition of a particular palladium source or 2.
• the active catalyst species can be obtained in the reaction mixture containing both catalyst compounds and the cross- coupling reaction partners in situ during the cross-coupling reaction in which a base is used in order to e. g. activate the palladium precatalyst or generate the active boronate species e. g . in the Suzuki-Miyaura reaction which is essential for the reaction.
• the POSS linked phosphonium salts can be obtained by simple conversion of different POSS-halides having different chain lengths (scheme 1 ) with a phosphine.
• the preferred bisadamantyl substituted phosphine is used since this phosphine substitution pattern is found in benchmark cataCXiumA ® , which has proven to be a superior ligand in particularly manifold palladium-catalyzed cross- coupling reactions.
• Connecting the POSS cube with bisadamantylphosphine via an unbranched alkyl chain leads to a ligand structure which is very close to that found in cataCXiumA ® .
• the salts can be obtained simple reactions starting from POSS-halides and corresponding imidazole (scheme 2, left).
• POSS-halides were added slowly two a melt of 10-30 fold excess of imidazol. Simple take- up of the crude product in water and extraction with ether gave the products in excellent yields and high purity.
• the mixed phosphine-imidazolium-based N HC type of ligands are obtained by conversion of the POSS-containing singly alkylated imidazolium salts by treating with phosphines or their mineral salts respectively:
• the symmetric POSS-substituted bis-imidazolium salts can be converted into the corresponding bis-NHC-transition metal complexes by treatment with a base and subsequent addition of an appropriate metal source.
• Palladium was taken as metal of choice for the synthesis of various carbene- and phosphine complexes and their employment in C- C- and C-N-coupling reactions.
• the POSS-based phosphine ligands were tested in a C-C cross-coupling reaction (Heck-Mizoroki reaction, scheme 5).
• n 1 0
• n 3 96
• the 31 P- and 1 H-NMR-spectra were measured on Bruker DRX 500 (500 MHz) spectrometer.
• the chemical shifts were given in ppm from tetramethylsilane as an internal standard (0.00 ppm) or the solvent residue peaks (CDCI 3 : 7.26 ppm, CD 2 CI 2 : 5.26 ppm).
• the chemical shifts of the 31 P resonances were determined relative to phosphoric acid (H 3 PO 4 ) a s an internal standard (0.00 ppm).
• Peak multiciplities were abbreviated as: s, singlet; d, investigatinget, t, triplet, qr, quartet, qn, quintet, sep, septet; m, multiplet. All solvents and chemicals were used as purchased. Reagents and solvents were purchased from Aldrich. All POSS sta rti ng m ateria l s were pu rch ased from Hybrid Cata lys is . Di-(1 - adamantyl)phosphine is an in-house product of EVONIK-DEGUSSA GmbH.

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