WO2018220003A1 - Hydrogenation of substituted furans catalyzed by nhc-containing ligands - Google Patents

Hydrogenation of substituted furans catalyzed by nhc-containing ligands Download PDF

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Publication number
WO2018220003A1
WO2018220003A1 PCT/EP2018/064171 EP2018064171W WO2018220003A1 WO 2018220003 A1 WO2018220003 A1 WO 2018220003A1 EP 2018064171 W EP2018064171 W EP 2018064171W WO 2018220003 A1 WO2018220003 A1 WO 2018220003A1
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transition metal
diyl
dimethanol
ligand
tetrahydrofuran
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PCT/EP2018/064171
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French (fr)
Inventor
Dominik Ohlmann
Thomas Schaub
Alban CADU
A. Stephen K. Hashmi
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Basf Se
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
    • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
    • C07D307/04—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having no double bonds between ring members or between ring members and non-ring members
    • C07D307/10—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having no double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
    • C07D307/12—Radicals substituted by oxygen atoms

Definitions

  • the present invention relates to a process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof to obtain a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol.
  • the invention also relates to a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol.
  • the invention also relates to a use of transition metal complex as hydrogenation catalyst for composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof.
  • the invention also relates to a use of the composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5- diyl)dimethanol for polymerization reactions.
  • HMF Hydroxymethylfurfural
  • bishydroxymethylfuran are organic compounds, which can be derived by conversion of certain sugars and carbohydrates. HMF can be converted into derivatives, which can serve, inter alia, as starting point for the synthesis of pharmaceuticals, polymers and macrocyclic compounds.
  • the derivatives cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol are of particular commercial interest, especially for the production of polymers.
  • US 2007/0287845 discloses a method for the reduction of HMF in a solvent comprising water.
  • hydrogenation catalyst a heterogeneous catalyst is employed comprising metals of the groups 8 to 10 of the periodic table of the elements according to lUPAC.
  • US 2007/0287845 re- lates to a method for a selective reduction of the aldehyde group of HMF.
  • Tetrahydrofuran-di- methanol (THFDM, 2,5-bis(hydroxymethyl)-tetrahydrofuran) is obtained as a by-product.
  • THFDM Tetrahydrofuran-di- methanol
  • firstly HMF is contacted with a first catalyst obtaining
  • THFDM furan dimethylol
  • heterogeneous catalysis differs from homogeneous catalysis in that the catalyst is in a different phase than the reactants.
  • the major advantage of homogeneous catalysts is the fact that every single catalytic entity can act as a single active site. Thus, homogeneous catalysis is usually more active and selective compared to heterogeneous catalysis.
  • the process it should be possible to provide an isomer mixture of cis/trans-2,5-bis(hydroxymethyl)-tetrahydrofuran in high yield.
  • the process should particularly allow for the production of trans-2,5-bis(hydroxymethyl)-tetrahydrofuran from hydroxymethylfurfural bishydroxymethylfuran or mixtures thereof with an improved regioselectivity. Very particularly, it should be possible to obtain trans-2,5-bis(hydroxymethyl)-tetrahydrofuran in the process in high yields.
  • the process should be performed economically without the need for many reaction steps. Further, the process should be performed as a homogeneously catalyzed hydrogenation of HMF.
  • This object is achieved by a process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof, particularly 5-hydroxymethyl-2- furfuralaldehyd (HMF), 2,5-bishydroxymethylfuran (BHMF), or mixtures thereof, to obtain a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5- diyl)dimethanol, which process comprises reacting the composition comprising hydroxymethyl- furfural, bishydroxymethylfuran or mixtures thereof with hydrogen in a liquid reaction medium comprising a transition metal complex catalyst in homogeneous solution, wherein the transition metal complex catalyst comprises a transition metal and at least one N-heterocyclic carbene lig- and (NHC-ligand) which is capable of coordinating to the transition metal and wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
  • HMF 5-
  • trans-(tetrahydrofuran-2,5-diyl)dimethanol refers to the isomers (2R,5R)-trans-tetrahydrofuran-2,5-diyldimethanol and (2S,5S)-trans-tetrahydrofuran-2,5-diyl- dimethanol and mixtures thereof in any mixing ratio.
  • alkyl means straight and branched alkyl groups. Preferred are straight or branched Ci-C2o-alkyl groups, more preferably Ci-Ci2-alkyl groups, even more preferably Ci-Cs-alkyl groups and in particular Ci-C6-alkyl groups.
  • alkyl groups are particularly methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n- pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, 2,2-dime- thylpropyl, 1 -ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1 ,2- dimethylbutyl, 1 ,3-dimethylbutyl, 2,3-dimethylbutyl, 1 ,1 -dimethylbutyl, 2,2-dimethylbutyl, 3,3-di- methylbutyl, 1 ,1 ,2-trimethylpropyl, 1 ,2,2-trimethylpropyl, 1 ,
  • alkyl comprises also substituted alkyl groups, which may carry 1 , 2, 3, 4 or 5 substituents, preferably 1 , 2 or 3 substituents and particularly preferably 1 substituent, selected from the groups cycloalkyl, aryl, hetaryl, halogen, NE 1 E 2 , (NE 1 E 2 E 3 ) + X-, COOH, carboxylate, SO3H and sulfonate, wherein E 1 , E 2 and E 3 are the same or different and are selected from hy- drogen, alkyl, cycloalkyl, and aryl and X " is an anion equivalent.
  • a preferred fluorinated alkyl group is trifluoromethyl.
  • alkyl also comprises alkyl groups which are interrupted by one or more non-adjacent oxygen atoms, preferably alkoxyalkyl.
  • alkylene in the sense of the present invention stands for straight or branched alkanediyl groups with preferably 1 to 6 carbon atoms. These are methylene (-CH2-), ethylene (- CH2-CH2-), n-propylene (-CH2-CH2-CH2-), isopropylene (-CH 2 -CH(CH 3 )-), etc.
  • cycloalkyl in the sense of the present invention comprises unsubstituted and substituted cycloalkyl groups, preferably C5-C7-cycloalkyl groups like cyclopentyl, cyclohexyl or cycloheptyl, which in case they are substituted may carry 1 , 2, 3, 4 or 5 substituents, preferably 1 , 2 or 3 substituents and particularly preferred 1 substituent selected from the groups alkyl, alkoxy and halogen.
  • heterocycloalkyl in the sense of the present invention comprises saturated or partially unsaturated cycloaliphatic groups with preferably 4 to 7, more preferably 5 or 6 ring atoms, in which 1 , 2, 3 or 4 ring atoms may be substituted with heteroatoms, preferably selected from the elements oxygen, nitrogen and sulfur and which are optionally substituted. In case they are substituted, these heterocycloaliphatic groups carry preferably 1 , 2 or 3 substituents, more preferably 1 or 2 substituents and in particular 1 substituent.
  • heterocycloaliphatic groups examples include pyrrolidinyl, piperidinyl, 2,2,6,6-tetramethylpiperidinyl, imidazolidinyl, pyrazolidinyl, oxazolidinyl, morpholidinyl, thiazoli- dinyl, isothiazolidinyl, isoxazolidinyl, piperazinyl, tetrahydrothiophenyl, tetrahydrofuranyl, tetrahy- dropyranyl and dioxanyl.
  • aryl in the sense of the present invention comprises unsubstituted and substi- tuted aryl groups and preferably stands for phenyl, tolyl, xylyl, mesityl, naphthyl, fluorenyl, an- thracenyl, phenanthrenyl or naphthacenyl, more preferably phenyl or naphthyl.
  • aryl groups may carry preferably 1 , 2, 3, 4 or 5 substituents, more preferably 1 , 2 or 3 substituents and particularly preferred 1 substituent.
  • substituents are preferably selected from the groups alkyl, alkoxy, carboxyl, carboxylate, trifluoromethyl, -SO3H, sul- fonate, NE 1 E 2 , alkylene-NE 1 E 2 , nitro, cyano and halogen.
  • a preferred fluorinated aryl group is pentafluorophenyl.
  • heterocycloaromatic groups preferably pyridyl, quinolinyl, acridinyl, pyridazinyl, pyrimidi- nyl, pyrazinyl, pyrrolyl, imidazolyl, pyrazolyl, indolyl, purinyl, indazolyl, benzotriazolyl, 1 ,2,3-tria- zolyl, 1 ,3,4-triazolyl and carbazolyl in which in case these heterocycloaromatic groups are substituted they may carry preferably 1 , 2 or 3 substituents selected from the groups alkyl, alkoxy, carboxyl, carboxylate, -SO3H, sulfonate, NE 1 E 2 , alkylene-NE 1 E 2 , trifluoromethyl and halogen.
  • a preferred substituted indolyl group is 3-methylin
  • Carboxylate and sulfonate in the sense of the present invention preferably stand for a derivative of a carboxylic acid function or a sulfonic acid function, in particular a metal carboxylate or metal sulfonate, a carboxylic acid ester or sulfonic acid ester or a carboxylic acid amide or sulfonic acid amide.
  • esters with Ci-C4-alkanols like methanol, ethanol, n-pro- panol, isopropanol, n-butanol, sec-butanol and tert-butanol.
  • Preferred are also the primary amides and their N-alkyl and ⁇ , ⁇ -dialkyl derivatives.
  • acyl in the sense of the present invention stands for alkanoyl groups or aroyl groups with preferably 2 to 1 1 , more preferably 2 to 8 carbon atoms, for example acetyl, propa- noyl, butanoyl, pentanoyl, hexanoyl, heptanoyl, 2-ethylhexanoyl, 2-propylheptanoyl, benzoyl and naphthoyl.
  • the group NE 1 E 2 is preferably selected from N,N-dimethylamino, ⁇ , ⁇ -diethylamino, N,N-diprop- ylamino, ⁇ , ⁇ -diisopropylamino, N,N-di-n-butylamino, N,N-di-tert-butylamino, N,N-dicyclohexyla- mino and N,N-diphenylamino.
  • Halogen stands for fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.
  • M + stands for a cation equivalent, which means a monovalent cation or the part of a polyvalent cation representing a positive single charge.
  • the cation M + is only a counter ion which neutralizes negatively charged substituents like the COO " or the sulfonate group and which can princi- pally be selected arbitrarily.
  • Preferred are alkaline metal ions, in particular Na + , K + and Li + ions, or onium ions like ammonium ions, mono-, di-, tri-, tetraalkylammonium ions, phosphonium ions, tetraalkylphosphonium ions and tetraarylphosphonium ions.
  • anion equivalent X- which is only a counter ion for positively charged substituents like the ammonium group and which can principally be selected arbitrarily among monovalent anions and the parts of polyvalent anions which correspond to a single negative charge.
  • halogenides X " in particular chloride and bromide.
  • sulfates and sulfonates in particular S0 4 2_ , tosylate, trifluoromethane sulfonate and methyl- sulfonate.
  • Condensed ring systems are aromatic, heteroaromatic or cyclic compounds which have fused- on rings obtained via anellation.
  • Condensed ring systems consist of two, three or more than three rings. Depending on the type of connection, one distinguishes between ortho-anellation and peri-anellation. In case of ortho-anellation each ring has two atoms in common with each adjacent ring. In case of peri-anellation a carbon atoms belongs to more than two rings.
  • Preferred among the condensed ring systems are ortho-condensed ring systems.
  • composition comprising hydroxmethylfurfural, bishydroxymethylfu- ran or mixtures thereof is a composition, wherein at least one component of the composition is 5-(hydroxmethyl)furfural (HMF), 2,5-bishydroxymethylfuran (BHMF).
  • HMF 5-(hydroxmethyl)furfural
  • BHMF 2,5-bishydroxymethylfuran
  • the composition consists of 5-(hydroxmethyl)furfural, e.g. HMF, without further components.
  • the composition consists of 2,5-bishydroxymethylfuran, e.g. BHMF, without further components.
  • the composition consists of 5-(hydroxmethyl)furfural and 2,5-bishydroxymethylfuran without further components.
  • composition comprising hydroxmethylfurfural
  • a ho- mogeneous transition metal catalyst complex is used. That means the transition metal catalyst complex is dissolved in the liquid reaction medium under the reaction condition. In other words, the transition metal catalyst complex is in the same phase as the reactants, in particular the composition comprising hydroxmethylfurfural, bishydroxymethylfuran or mixtures thereof.
  • the liquid reaction medium can comprise at least one ligand in excess. In this embodiment the liquid reaction contains free ligands that are not bound to the transition metal complex.
  • the free ligands are selected from the N-heterocyclic carbene ligands (NHC-ligands) defined in the following.
  • the transition metal of the transition metal catalyst complex is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
  • the metal of the transition metal catalyst complex is selected from ruthenium, rhodium, iridium, nickel, platinum and palladium, in particular ruthenium and nickel, especially ruthenium.
  • the inventive process is characterized in that the transition metal is selected from the group consisting of ruthenium, rhodium, iridium, nickel, platinum and palladium, preferably ruthenium and nickel, in particular ruthenium.
  • the transition metal catalyst complex comprises, beside the transition metal, at least one N-heterocyclic carbene ligand (NHC-ligand) which is capable of coordinating to the transition metal.
  • N-heterocyclic carbene ligand N-heterocyclic carbene ligand
  • Carbenes in particular persistent carbenes, are known as neutral ligands, which are capable of coordinating to transition metals.
  • carbenes which are stabilized by at least one nitrogen atom, for example carbenes of formula (l-A) are able to coordinate to different transition metals.
  • R where Y is a C or a heteroatom selected from the group of elements consisting of N, O, S and P, preferably N, is 1 . is 0 when Y is O or S, q is 1 when Y is N or P, and q is 2 when Y is C,
  • Q 1 , Q 2 , Q 3 , Q 4 are each, independently of one another, a divalent organic group having from
  • R 3 , R 3A , R 4 and R 4A can be identical or different and are each, independently of one another, hydrogen or a C1-C40 radical, for example Ci-C2o-alkyl, C2-C2o-alkenyl, C2-C2o-alkynyl, C5-C4o-aryl, C7-C4o-alkylaryl, C7-C4o-arylalkyl, C2-C4o-heteroaromatic radical, saturated C3-C2o-heterocyclic radical or silyl radical having from 3 to 24 carbon atoms, where the carbon-comprising radical can comprise further heteroatoms selected from the group of elements consisting of F, CI, Br, I, N, P, O and S and/or be substituted by functional groups, or two radicals R 3A and R 4A are joined to one another and together form Q, a divalent organic group having from 1 to 40 carbon atoms.
  • a C1-C40 radical for example Ci-
  • Q 1 , Q 2 , Q 3 , Q 4 are each, independently of one another, a divalent organic group having from 1 to 40 carbon atoms, where, in addition, two or more substituents on adjacent atoms within Q 1 , Q 2 , Q 3 and/or Q 4 can be joined to one another to form an additional cyclic or polycyclic structure.
  • the divalent organic group having from 1 to 40 carbon atoms can be, for example, a divalent hydrocarbon group, a substituted divalent hydrocarbon group, a divalent heteroatom-com- prising hydrocarbon group, a substituted and at the same time heteroatom-comprising divalent hydrocarbon group or -(CO)-.
  • the transition metal catalyst complex comprises, beside the transition metal, at least one N-het- erocyclic carbene ligand (NHC-ligand) which is capable of coordinating to the transition metal.
  • the process of the invention is carried out using a transition metal complex in which at least one N-heterocyclic carbene ligand (NHC-ligand) coordinates to the transition metal, for examples carbenes of the formula (l-A) in which w, x, y, z are each 0, p is 1 , q is 1 when Y is N and q is 2 when Y is C,
  • Y is C or N, preferably N, and two radicals R 3A and R 4A are joined to one another and together form Q, a divalent organic group having from 1 to 40 carbon atoms.
  • Suitable heterocyclic carbene ligands are for example represented by the following general structures, wherein R 3 , R 4 or R 4A are defined as described above:
  • the inventive process is characterized in that the N heterocyclic carbene ligand (NHC-ligand) is selected from imidazol-2-ylidenes, triazol-5-yli- denes, imidazolidine-2-ylidenes, and tetrahydropyrimidin-2-ylidenes, which are substituted or unsubstituted, preferably substituted.
  • NHC-ligand N heterocyclic carbene ligand
  • the inventive process is characterized in that the N heterocyclic carbene ligand (NHC-ligand) is defined by general formula (I)
  • R 1 and R 2 are independently from each other alkyl, cycloalkyi, heterocycloalkyi, aryl or hetaryl, wherein the alkyl radicals may carry 1 , 2, 3, 4 or 5 substituents selected from cycloalkyi, heterocycloalkyi, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, he- taryloxy, hydroxy, mercapto, polyalkylene oxide, polyalkyleneimine, carboxyl, SO3H, sul- fonate, NE 1 E 2 , NE 1 E 2 E 3+ X ⁇ , halogen, nitro, formyl, acyl and cyano, wherein E 1 , E 2 and E 3 are the same or different and are selected from hydrogen, alkyl, cycloalkyi, and aryl and X " is an anion equivalent,
  • radicals cycloalkyi, heterocycloalkyi, aryl and hetaryl R 1 and R 2 may carry 1 , 2, 3, 4 or 5 substituents selected from alkyl and the substituents mentioned for the alkyl radicals R 1 and R 2 ,
  • the inventive process is characterized in that the N- heterocyclic carbene ligand (NHC-ligand) is selected from the formulas A to I and mixtures thereof
  • the transition metal complex catalyst of the process of the invention can be employed in the form of a preformed metal complex which comprises a transition metal and at least one
  • the transition metal complex catalyst is formed in situ in the reaction medium by combining a metal compound, herein also termed pre-catalyst, with one or more suitable N-heterocyclic carbene ligand (NHC-ligand) to form a catalytically active metal complex, the transition metal complex catalyst, in the reaction medium. It is also possible that the transition metal complex catalyst is formed in situ in the reaction medium by combining a pre-catalyst with one or more NHC-precursor, in particular the protonated form of a NHC-ligand, which is in situ converted to the corresponding NHC-ligand, to form a catalytically active metal complex in the reaction medium.
  • the inventive process is characterized in that the N- heterocyclic carbene ligand (NHC-ligand) is prepared in situ by using the corresponding proto- nated form according to formula II,
  • the transition metal complex catalyst is prepared in situ by using the corresponding protonated form according to formula II, a base and a transition metal complex, which does not comprise any heterocyclic carbene ligand.
  • Suitable bases for deprotonating the protonated form of different NHC ligands according to for- mula II are described by de Fremont et al., Coordination Chemistry Reviews 253 (2009) 876 to 881 .
  • the deprotonation of the protonated forms of NHC ligands can be carried out in ammonia or in non-protic solvents such as THF or ethers.
  • the deprotonation requires anhydrous conditions and the use of strong bases, with pK a values above 14.
  • potassium or sodium hydride with a catalytic amount of tert-butoxide is employed, but tert-butoxide itself, lithium alumi- num hydride, n-butyllithium, potassium hexamethyldisilazide (KHMDS) and 1 ,8-diazabicy- clo[5.4.0]undec-7-ene (DBU) are also efficient alternatives.
  • tert-butoxide lithium alumi- num hydride, n-butyllithium, potassium hexamethyldisilazide (KHMDS) and 1 ,8-diazabicy- clo[5.4.0]undec-7-ene (DBU) are also efficient alternatives.
  • Suitable pre-catalysts are selected from neutral metal complexes, oxides and salts of metals of groups 8, 9 and 10 of the periodic table of the elements.
  • Preferred pre-catalysts are selected from metal complexes, oxides and salts of ruthenium, rhodium, iridium, nickel, platinum or palladium.
  • Ruthenium compounds that are useful as pre-catalyst are, for example, [Ru(methylallyl)2COD], [Ru(p-cymene)CI 2 ]2, [Ru(benzene)CI 2 ]n, [Ru(CO) 2 CI 2 ]n, [Ru(CO) 3 CI 2 ] 2 , [Ru(COD)(allyl)], [RuCly H 2 0], [Ru(acetylacetonate) 3 ], [Ru(DMSO) 4 CI 2 ], [Ru(PPh 3 ) 3 (CO)(H)CI], [Ru(PPh 3 ) 3 (CO)CI 2 ], [Ru(PPh 3 ) 3 (CO)CI 2 ], [Ru(PPh 3 ) 3 (CO)(H) 2 ], [Ru(PPh 3 ) 3 CI 2 ], [Ru(Cp)(PPh 3 ) 2 CI], [Ru(Cp)(CO) 2 CI], [Ru(Cp)(CO) 2 H],
  • Iridium compounds that are useful as pre-catalyst are, for example, [lrCI 3 -H 2 0], KlrCI 4 , K 3 lrCl6, [lr(COD)CI] 2 , [lr(cyclooctene) 2 CI] 2 , [lr(ethene) 2 CI] 2 , [lr(Cp)CI 2 ] 2 , [lr(Cp * )CI 2 ] 2 , [lr(Cp)(CO) 2 ],
  • Nickel compounds that are useful as pre-catalyst are, for example [Ni(COD) 2 ], Ni(CO) 4 , NiCI 2 , NiBr 2 , Nil 2 , Ni(OAc) 2 [Ni(AcAc) 2 ], [Ni(CI) 2 (TMEDA)], [Ni(CI) 2 (DME)], [Ni(Br) 2 (DME)],
  • Rhodium compounds that are useful as pre-catalyst are, for example rhodium(ll) salts and rho- dium(lll) salts like rhodium(ll) carboxylate and rhodium(lll) carboxylate, rhodium(ll) acetate and rhodium(lll) acetate, rhodiumbiscarbonylacetylacetonate, acetylacetonatobisethylenerhodium(l) acetylacetonatocyclooctadienylrhodium(l), acetylacetonatonorbornadienylrhodium(l), acetyl- acetonatocarbonyltriphenylphosphinerhodium(l).
  • rhodium(ll) salts and rho- dium(lll) salts like rhodium(ll) carboxylate and rhodium(lll)
  • Platinum compounds that are useful as pre-catalyst are, for example ammonium tetrachloroplat- inate(ll), bis(tri-t-butylphosphine)platinum (0), bis(ethylenediamine)platinum(ll) chloride, di- bromo(1 ,5-cyclooctadiene)platinum(ll), dichlorobis(benzonitrile)platinum(ll), cis-dichlorobis(di- ethylsulfide)platinum(ll), cis-dichlorobis(pyridine)platinum(ll), cis-dichlorobis(tri- ethylphosphine)platinum(ll), dichloro(1 ,5-cyclooctadiene)platinum(ll), cis-dichlorodiammine plat- inum(ll), di- ⁇ -chloro-dichlorobis(ethylene)diplatinum(ll), dichlor
  • Palladium compounds that are useful as pre-catalyst are, for example allyl(cyclopentadienyl)pal- ladium(ll), bis[(trimethylsilyl)methyl](1 ,5-cyclooctadiene)palladium(ll), allylpalladium chloride di- mer, ammonium tetrachloropalladate(ll), bis[1 ,2-bis(diphenylphosphino)ethane]palladium(0), bis(dibenzylideneacetone)palladium(0), trans-bis(dicyclohexylamine)bis(acetato)palladium(ll), bis(2-methylallyl)palladium chloride dimer, bis(tri-t-butylphosphine)palladium(0), bis(tricyclohex- ylphosphine)palladium(O), bis(tri-o-tolylphosphine)palladium(0), chloromethyl(1 ,5-cycl
  • COD denotes 1 ,5-cyclooctadiene
  • Cp denotes cy- clopentadienyl
  • Cp * denotes pentamethylcyclopentadienyl
  • binap denotes 2,2'-bis(diphe- nylphosphino)-1 ,1 '-binaphthyl.
  • a substoichiometric amount of transition metal complex catalyst is generally used, with the amount of transition metal complex catalyst typically being not more than 50 mol%, frequently not more than 20 mol% and in particular not more than 10 mol% or not more than 5 mol%, based on the amount of hydrogenable composition selected from hy- droxymethylfurfural, bishydroxymethylfuran and mixtures thereof.
  • An amount of catalyst of from 0.001 to 50 mol%, frequently from 0.001 mol% to 20 mol% and in particular from 0.005 to
  • the inventive process is characterized in that the transition metal complex catalyst is used in an amount of 0.001 mol% to 20 mol%, calculated as transition metal and based on the sum of the amounts of hydroxymethylfurfural and of bishydroxymethylfuran used in the process.
  • the process of the invention is generally carried out at temperatures in the range from -20 °C to 300 °C, preferably in the range from 50 °C to 200 °C and particularly preferably in the range from 80 °C to 180 °C. Temperatures below 150 °C have surprisingly been found to be particularly advantageous.
  • Suitable solvents are selected from aliphatic hydrocarbons, aromatic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof.
  • Preferred solvents are aliphatic hydrocarbons such as pentane, hexane, heptane, octane or cyclohexane;
  • aromatic hydrocarbons such as benzene, toluene, xylenes, ethylbenzene, mesitylene or benzotrifluoride;
  • amides such as dimethylformamide, diethylformamide, /V-methylpyrrolidone, N-ethylpyrrol- idone or dimethylacetamide;
  • ureas such as tetramethylurea, ⁇ , ⁇ -dimethylimidazolinone (DMI) and N,N-dimethylpropyl- eneurea (DMPU);
  • nitriles such as acetonitrile or propionitrile
  • sulfoxides such as dimethyl sulfoxide
  • alcohols such as methanol, ethanol, propanol or isopropanol
  • esters such as methyl acetate, ethyl acetate, f-butyl acetate;
  • carbonates such as diethyl carbonate, ethylene carbonate and propylene carbonate
  • ethers such as dioxane, tetrahydrofuran, diethyl ether, dibutyl ether, methyl f-butyl ether, diisopropyl ether or diethylene glycol dimethyl ether;
  • mixtures of two or more of the afore-mentioned solvents can also be used. Preference is given to using aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof as solvents.
  • the inventive process is characterized in that the reaction is carried out in the presence of a solvent selected from aliphatic hydrocarbons, aro- matic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof.
  • a solvent selected from aliphatic hydrocarbons, aro- matic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof.
  • the hydrogenation can principally be performed according to all processes known to a person skilled in the art which are suitable for the hydrogenation of a HMF-comprising composition.
  • the hydrogen used for the hydrogenation can be used in pure form or, if desired, also in the form of mixtures with other, preferably inert gases, such as nitrogen or argon. Preference is given to using hydrogen in undiluted form.
  • the hydrogenation is typically carried at a hydrogen pressure in the range from 0.1 to 200 bar, preferably in the range from 1 to 50 bar, more preferably in the range from 1 to 15 bar.
  • the hydrogenation can principally be performed continuously, semi-continuously or discontinu- ously. Preference is given to a continuous process.
  • the hydrogenation can principally be performed in all reactors known by a person in the art for this type of reaction and therefore, will select the reactors accordingly. Suitable reactors are described and reviewed in the relevant prior art, e.g. appropriate monographs and reference works such as mentioned in US 66391 14 B2, column 16, line 45-49.
  • an autoclave is employed which may have an internal stirrer and an internal lining.
  • composition obtained in the hydrogenation process of the invention comprises cis-(tetrahy- drofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol.
  • the obtained composition comprises cis- (tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, wherein the ratio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimethanol is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1 .
  • the inventive process is characterized in that the molar ratio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimetha- nol after finishing the process of hydrogenation is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1 .
  • a further aspect of the invention relates to a composition comprising cis-(tetrahydrofuran-2,5- diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol obtained by the process according to the invention and described above.
  • the invention relates also to the composition obtained by the process according to the invention and described above comprising cis-(tet- rahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, wherein the ra- tio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimethanol is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1.
  • a further aspect of the invention is the use of a transition metal complex comprising a transition metal and at least one N-heterocyclic carbine ligand (NHC-ligand), which is capable of coordi- nating to the transition metal, such as described above, as hydrogenation catalyst for compositions comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof, wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
  • N-heterocyclic carbine ligand N-heterocyclic carbine ligand
  • a further aspect of the invention is the use of the composition comprising cis-(tetrahydrofuran- 2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, obtained by the process according to the invention and described above for polymerization reactions.
  • the work-up of the reaction mixture obtained in the hydrogenation of the inventive process and the isolation of cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)di- methanol are effected in a customary manner, for example by filtration, an aqueous extractive work-up or by a distillative separation, for example under reduced pressure.
  • the cis-(tetrahydro- furan-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol may be obtained in sufficient purity by applying such measures or a combination thereof, obviating additional purification steps. Alternatively, further purification can be accomplished by methods commonly used in the art, such as chromatography.
  • Ru(methylallyl)2(COD) is also known as (1 ,5-Cyclooctadiene)bis(2-methylallyl)ruthenium (II).
  • RuC (COD) is also known as (1 ,5-Cyclooctadiene)dichloro-ruthenium (II) and
  • Ru(PPh3)3(CO)HCI is also known as tris(triphenylphosphine)ruthenium(ll) carbonyl chloride hydride.
  • Typical screening reactions were done based on a synthetic method described by S. Urban, N. Ortega, F. Glorius, Angew. Chem. Int. Ed. 201 1 , 50, 3803-3806.
  • the vial was stirred or sonicated until full dissolution of the HMF and the solution was transferred to an N2 purged glass autoclave, under a flow of N2.
  • the autoclave was tightly closed, purged with N2 then H2 (typically, 3 times each, 5 bars), and finally pressurized with H2 to the desired pressure.
  • An oil bath was used to bring the autoclave to the desired temperature (at 120°C, unless specified otherwise), and was stirred for the specified duration (typically overnight).
  • a sample was collected (while the autoclave was still at the indicated temperature), the solvent was removed in vacuo, the resulting oil was dissolved in D 6 -DMSO and analyzed by NMR.
  • the ratio of HMF : BHMF : THF-DM was determined by 1 H NMR, and the ratio of cis : trans THF-DM was determined by integration of the relevant carbon peaks by 13 C NMR, as described in the literature (based on an analytic method described by G. Bottari, A. J. Kumalaputri, K. K. Krawczyk, B. L. Feringa,H. J. Heeres, K. Barta, ChemSusChem 2015, 8, 1323 - 1327).
  • Table 1 summarizes the result of the different hydrogenation experiments. In each case the re- suit of the hydrogenation is reported as a ratio of the starting material (HMF), the intermediate (BHMF) and the desired product (THF-glycol). The amount of BHMF is normalized to 1 to facilitate comparison of the results.

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Abstract

The present invention relates to a process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof to obtain a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanoland trans-(tetrahydrofuran-2,5-diyl)dimethanol. The invention also relates to a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol. Further, the invention also relates to a use of transition metal complex as hydrogenation catalyst for composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof. The invention also relates to a use of the composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol for polymerization reactions.

Description

Hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof
Description
The present invention relates to a process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof to obtain a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol. The invention also relates to a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol. Further, the invention also relates to a use of transition metal complex as hydrogenation catalyst for composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof. The invention also relates to a use of the composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5- diyl)dimethanol for polymerization reactions.
Hydroxymethylfurfural (HMF) and bishydroxymethylfuran are organic compounds, which can be derived by conversion of certain sugars and carbohydrates. HMF can be converted into derivatives, which can serve, inter alia, as starting point for the synthesis of pharmaceuticals, polymers and macrocyclic compounds. The derivatives cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol are of particular commercial interest, especially for the production of polymers.
In the prior arts different approaches for the hydrogenation of hydroxymethylfurfural in order to obtain cis/trans-(tetrahydrofuran-2,5-diyl)dimethanol (2,5-bis(hydroxymethyl)-tetrahydrofuran, THF-glycol) have been suggested.
US 2007/0287845 discloses a method for the reduction of HMF in a solvent comprising water. As hydrogenation catalyst a heterogeneous catalyst is employed comprising metals of the groups 8 to 10 of the periodic table of the elements according to lUPAC. US 2007/0287845 re- lates to a method for a selective reduction of the aldehyde group of HMF. Tetrahydrofuran-di- methanol (THFDM, 2,5-bis(hydroxymethyl)-tetrahydrofuran) is obtained as a by-product. To increase the yield of THFDM, firstly HMF is contacted with a first catalyst obtaining
bishydroxymethylfuran (also termed as furan dimethylol (FDM)), which is contacted with a second catalyst to yield THFDM. However, the cis/trans ratio of THFDM has not been specified.
Connolly et al., Organic Process Research & Development 2010, 14, 459-465, discloses a multi-step process for the production of 8-oxa-3-aza-bicyclo[3.2.1 ]octane hydrochloride, wherein 5-hydroxymethyl-2-furfural (HMF) is used. Raney-nickel or Pd/C was used to catalyze the hydrogenation. As intermediates cis- and trans-2,5-bis(hydroxymethyl)-tetrahydrofuran are formed, wherein the cis configuration of 2,5-bis(hydroxymethyl)-tetrahydrofuran is predominant and the trans-isomer of the 2,5-bis(hydroxymethyl)-tetrahydrofuran is formed in very low yields. Rauchfuss et al., ChemSusChem 2010, 3, 1 139-1 141 , discloses a process for the preparation of hydroxymethylfurans from sugars, particularly a process for the preparation of 2,5-bis(hy- droxymethyl)furan (BHMF), which is obtained by the hydrogenation of HMF. The hydrogenation is performed in the presence of an iridium catalyst and in the presence of formic acid as a hy- drogen source.
The processes of the prior art are connected with various disadvantages. One disadvantage of processes based on heterogeneous catalysis is based on the fact that heterogeneous catalysis differs from homogeneous catalysis in that the catalyst is in a different phase than the reactants. The major advantage of homogeneous catalysts is the fact that every single catalytic entity can act as a single active site. Thus, homogeneous catalysis is usually more active and selective compared to heterogeneous catalysis.
The yields of the 2,5-bis(hydroxymethyl)-tetrahydrofuran derivatives obtained by the processes of the prior art are very low even if 2,5-bis(hydroxymethyl)-tetrahydrofuran derivatives are obtained, regioselectivity is not satisfactory. In known hydrogenation processes of HMF the regioselectivity for the trans-(tetrahydrofuran-2,5-diyl)dimethanol (trans-2,5-bis(hydroxymethyl)-tet- rahydrofuran) over the cis-(tetrahydrofuran-2,5-diyl)dimethanol (cis-2,5-bis(hydroxymethyl)-tet- rahydrofuran) is generally not satisfactory. The processes of the prior art do not selectively pro- duce 2,5-bis(hydroxymethyl)-tetrahydrofuran, let alone trans-2,5-bis(hydroxymethyl)-tetrahydro- furan, but to the contrary lead predominantly to the cis-2,5-bis(hydroxymethyl)-tetrahydrofuran derivative. Further, many of the processes of the prior art are energy and time consuming multi- step reactions. Accordingly, it is an object of the invention to provide a process for the production of cis-(tetra- hydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol from compositions comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof with an improved regioselectivity for the trans-2,5-Bis(hydroxymethyl)-tetrahydrofuran derivative compared with the state of the art. With the process it should be possible to provide an isomer mixture of cis/trans-2,5-bis(hydroxymethyl)-tetrahydrofuran in high yield. Furthermore, the process should particularly allow for the production of trans-2,5-bis(hydroxymethyl)-tetrahydrofuran from hydroxymethylfurfural bishydroxymethylfuran or mixtures thereof with an improved regioselectivity. Very particularly, it should be possible to obtain trans-2,5-bis(hydroxymethyl)-tetrahydrofuran in the process in high yields. The process should be performed economically without the need for many reaction steps. Further, the process should be performed as a homogeneously catalyzed hydrogenation of HMF.
This object is achieved by a process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof, particularly 5-hydroxymethyl-2- furfuralaldehyd (HMF), 2,5-bishydroxymethylfuran (BHMF), or mixtures thereof, to obtain a composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5- diyl)dimethanol, which process comprises reacting the composition comprising hydroxymethyl- furfural, bishydroxymethylfuran or mixtures thereof with hydrogen in a liquid reaction medium comprising a transition metal complex catalyst in homogeneous solution, wherein the transition metal complex catalyst comprises a transition metal and at least one N-heterocyclic carbene lig- and (NHC-ligand) which is capable of coordinating to the transition metal and wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
In the following some compounds are depicted.
Starting materials:
Figure imgf000004_0001
5-Hydroxymethyl-2-furfural (HMF) 2,5-Bishydroxymethylfuran (BHMF) Hydrogenation products:
Figure imgf000004_0002
(2S,5S) trans-(tetrahydrofuran-2,5-diyl)- (2R,5R) trans-(tetrahydrofuran-2,5-diyl)- dimethanol dimethanol
Figure imgf000004_0003
cis-(tetrahydrofuran-2,5-diyl)- dimethanol
In the sense of the invention, trans-(tetrahydrofuran-2,5-diyl)dimethanol refers to the isomers (2R,5R)-trans-tetrahydrofuran-2,5-diyldimethanol and (2S,5S)-trans-tetrahydrofuran-2,5-diyl- dimethanol and mixtures thereof in any mixing ratio.
In the sense of the invention, the expressions 5-(hydroxymethyl)furan-2-carbaldehyde, 5- droxy-2-furfural and HMF are used synonymously. In the sense of the invention, the expressions (tetrahydrofuran-2,5-diyl)dimethanol, THF-DM, 2,5-bis(hydroxymethyl)-tetrahydrofuran, THF-glycol are used synonymously.
In the sense of the invention, the expressions bishydroxymethylfuran, BHMF, furandimethanol or furandimethylol are used synonymously.
In the sense of the invention, the expressions furan-2,5-diyldimethanol, 2,5-bishydroxymethylfu- ran, [5-(hydroxymethyl)-2-furyl]methanol and BHMF are used synonymously. In the sense of the invention, the expression "alkyl" means straight and branched alkyl groups. Preferred are straight or branched Ci-C2o-alkyl groups, more preferably Ci-Ci2-alkyl groups, even more preferably Ci-Cs-alkyl groups and in particular Ci-C6-alkyl groups. Examples of alkyl groups are particularly methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n- pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, 2,2-dime- thylpropyl, 1 -ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1 ,2- dimethylbutyl, 1 ,3-dimethylbutyl, 2,3-dimethylbutyl, 1 ,1 -dimethylbutyl, 2,2-dimethylbutyl, 3,3-di- methylbutyl, 1 ,1 ,2-trimethylpropyl, 1 ,2,2-trimethylpropyl, 1 -ethylbutyl, 2-ethylbutyl, 1 -ethyl-2- methylpropyl, n-heptyl, 2-heptyl, 3-heptyl, 2-ethylpentyl, 1 -propylbutyl, n-octyl, 2-ethylhexyl, 2- propylheptyl, nonyl and decyl.
The expression "alkyl" comprises also substituted alkyl groups, which may carry 1 , 2, 3, 4 or 5 substituents, preferably 1 , 2 or 3 substituents and particularly preferably 1 substituent, selected from the groups cycloalkyl, aryl, hetaryl, halogen, NE1E2, (NE1E2E3)+ X-, COOH, carboxylate, SO3H and sulfonate, wherein E1, E2 and E3 are the same or different and are selected from hy- drogen, alkyl, cycloalkyl, and aryl and X" is an anion equivalent. A preferred fluorinated alkyl group is trifluoromethyl. The expression "alkyl" also comprises alkyl groups which are interrupted by one or more non-adjacent oxygen atoms, preferably alkoxyalkyl.
The expression "alkylene" in the sense of the present invention stands for straight or branched alkanediyl groups with preferably 1 to 6 carbon atoms. These are methylene (-CH2-), ethylene (- CH2-CH2-), n-propylene (-CH2-CH2-CH2-), isopropylene (-CH2-CH(CH3)-), etc.
The expression "cycloalkyl" in the sense of the present invention comprises unsubstituted and substituted cycloalkyl groups, preferably C5-C7-cycloalkyl groups like cyclopentyl, cyclohexyl or cycloheptyl, which in case they are substituted may carry 1 , 2, 3, 4 or 5 substituents, preferably 1 , 2 or 3 substituents and particularly preferred 1 substituent selected from the groups alkyl, alkoxy and halogen.
The expression "heterocycloalkyl" in the sense of the present invention comprises saturated or partially unsaturated cycloaliphatic groups with preferably 4 to 7, more preferably 5 or 6 ring atoms, in which 1 , 2, 3 or 4 ring atoms may be substituted with heteroatoms, preferably selected from the elements oxygen, nitrogen and sulfur and which are optionally substituted. In case they are substituted, these heterocycloaliphatic groups carry preferably 1 , 2 or 3 substituents, more preferably 1 or 2 substituents and in particular 1 substituent. These substituents are preferably selected from alkyl, cycloalkyl, aryl, COOR (R = H, alkyl, cycloalkyl, aryl), COO M+ and NE1 E2, more preferably alkyl. Examples of such heterocycloaliphatic groups are pyrrolidinyl, piperidinyl, 2,2,6,6-tetramethylpiperidinyl, imidazolidinyl, pyrazolidinyl, oxazolidinyl, morpholidinyl, thiazoli- dinyl, isothiazolidinyl, isoxazolidinyl, piperazinyl, tetrahydrothiophenyl, tetrahydrofuranyl, tetrahy- dropyranyl and dioxanyl.
The expression "aryl" in the sense of the present invention comprises unsubstituted and substi- tuted aryl groups and preferably stands for phenyl, tolyl, xylyl, mesityl, naphthyl, fluorenyl, an- thracenyl, phenanthrenyl or naphthacenyl, more preferably phenyl or naphthyl. In case these aryl groups are substituted they may carry preferably 1 , 2, 3, 4 or 5 substituents, more preferably 1 , 2 or 3 substituents and particularly preferred 1 substituent. These substituents are preferably selected from the groups alkyl, alkoxy, carboxyl, carboxylate, trifluoromethyl, -SO3H, sul- fonate, NE1E2, alkylene-NE1 E2, nitro, cyano and halogen. A preferred fluorinated aryl group is pentafluorophenyl.
The expression "hetaryl" in the sense of the present invention comprises unsubstituted or substituted heterocycloaromatic groups, preferably pyridyl, quinolinyl, acridinyl, pyridazinyl, pyrimidi- nyl, pyrazinyl, pyrrolyl, imidazolyl, pyrazolyl, indolyl, purinyl, indazolyl, benzotriazolyl, 1 ,2,3-tria- zolyl, 1 ,3,4-triazolyl and carbazolyl in which in case these heterocycloaromatic groups are substituted they may carry preferably 1 , 2 or 3 substituents selected from the groups alkyl, alkoxy, carboxyl, carboxylate, -SO3H, sulfonate, NE1 E2, alkylene-NE1 E2, trifluoromethyl and halogen. A preferred substituted indolyl group is 3-methylindolyl.
Carboxylate and sulfonate in the sense of the present invention preferably stand for a derivative of a carboxylic acid function or a sulfonic acid function, in particular a metal carboxylate or metal sulfonate, a carboxylic acid ester or sulfonic acid ester or a carboxylic acid amide or sulfonic acid amide. Particularly preferred are esters with Ci-C4-alkanols like methanol, ethanol, n-pro- panol, isopropanol, n-butanol, sec-butanol and tert-butanol. Preferred are also the primary amides and their N-alkyl and Ν,Ν-dialkyl derivatives.
The above statements regarding the expressions "alkyl", "cycloalkyl", "aryl", "heterocycloalkyl" and "hetaryl" apply accordingly to the expressions "alkoxy", "cycloalkoxy", "aryloxy", "heterocy- cloalkoxy" and "hetaryloxy".
The expression "acyl" in the sense of the present invention stands for alkanoyl groups or aroyl groups with preferably 2 to 1 1 , more preferably 2 to 8 carbon atoms, for example acetyl, propa- noyl, butanoyl, pentanoyl, hexanoyl, heptanoyl, 2-ethylhexanoyl, 2-propylheptanoyl, benzoyl and naphthoyl. The group NE1E2 is preferably selected from N,N-dimethylamino, Ν,Ν-diethylamino, N,N-diprop- ylamino, Ν,Ν-diisopropylamino, N,N-di-n-butylamino, N,N-di-tert-butylamino, N,N-dicyclohexyla- mino and N,N-diphenylamino. Halogen stands for fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine.
M+ stands for a cation equivalent, which means a monovalent cation or the part of a polyvalent cation representing a positive single charge. The cation M+ is only a counter ion which neutralizes negatively charged substituents like the COO" or the sulfonate group and which can princi- pally be selected arbitrarily. Preferred are alkaline metal ions, in particular Na+, K+ and Li+ ions, or onium ions like ammonium ions, mono-, di-, tri-, tetraalkylammonium ions, phosphonium ions, tetraalkylphosphonium ions and tetraarylphosphonium ions.
The same applies to the anion equivalent X- which is only a counter ion for positively charged substituents like the ammonium group and which can principally be selected arbitrarily among monovalent anions and the parts of polyvalent anions which correspond to a single negative charge. Preferred are halogenides X", in particular chloride and bromide. Also preferred are sulfates and sulfonates, in particular S04 2_, tosylate, trifluoromethane sulfonate and methyl- sulfonate.
Condensed ring systems are aromatic, heteroaromatic or cyclic compounds which have fused- on rings obtained via anellation. Condensed ring systems consist of two, three or more than three rings. Depending on the type of connection, one distinguishes between ortho-anellation and peri-anellation. In case of ortho-anellation each ring has two atoms in common with each adjacent ring. In case of peri-anellation a carbon atoms belongs to more than two rings. Preferred among the condensed ring systems are ortho-condensed ring systems.
In the sense of the invention composition comprising hydroxmethylfurfural, bishydroxymethylfu- ran or mixtures thereof is a composition, wherein at least one component of the composition is 5-(hydroxmethyl)furfural (HMF), 2,5-bishydroxymethylfuran (BHMF). In a particular embodiment the composition consists of 5-(hydroxmethyl)furfural, e.g. HMF, without further components. In another particular embodiment the composition consists of 2,5-bishydroxymethylfuran, e.g. BHMF, without further components. In another particular embodiment the composition consists of 5-(hydroxmethyl)furfural and 2,5-bishydroxymethylfuran without further components.
In the process of the invention, the composition comprising hydroxmethylfurfural,
bishydroxymethylfuran or mixtures thereof, in particular 5-(hydroxmethyl)furfural (HMF), 2,5- bishydroxymethylfuran or mixtures thereof, is subjected to a hydrogenation in a liquid reaction medium in the presence of a transition metal catalyst complex. According to the invention, a ho- mogeneous transition metal catalyst complex is used. That means the transition metal catalyst complex is dissolved in the liquid reaction medium under the reaction condition. In other words, the transition metal catalyst complex is in the same phase as the reactants, in particular the composition comprising hydroxmethylfurfural, bishydroxymethylfuran or mixtures thereof. Further the liquid reaction medium can comprise at least one ligand in excess. In this embodiment the liquid reaction contains free ligands that are not bound to the transition metal complex. The free ligands are selected from the N-heterocyclic carbene ligands (NHC-ligands) defined in the following.
The transition metal of the transition metal catalyst complex is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC. In a preferred embodiment the metal of the transition metal catalyst complex is selected from ruthenium, rhodium, iridium, nickel, platinum and palladium, in particular ruthenium and nickel, especially ruthenium.
In one embodiment of the present invention, the inventive process is characterized in that the transition metal is selected from the group consisting of ruthenium, rhodium, iridium, nickel, platinum and palladium, preferably ruthenium and nickel, in particular ruthenium.
The transition metal catalyst complex comprises, beside the transition metal, at least one N-heterocyclic carbene ligand (NHC-ligand) which is capable of coordinating to the transition metal.
Carbenes, in particular persistent carbenes, are known as neutral ligands, which are capable of coordinating to transition metals. In particular, carbenes, which are stabilized by at least one nitrogen atom, for example carbenes of formula (l-A) are able to coordinate to different transition metals.
R
Figure imgf000008_0001
where Y is a C or a heteroatom selected from the group of elements consisting of N, O, S and P, preferably N, is 1 . is 0 when Y is O or S, q is 1 when Y is N or P, and q is 2 when Y is C,
Q1, Q2, Q3, Q4 are each, independently of one another, a divalent organic group having from
1 to 40 carbon atoms, where, in addition, two or more substituents on adjacent atoms within Q1, Q2, Q3 and/or Q4 can be joined to one another to form an additional cyclic or polycyclic structure, w, x, y, z are each, independently of one another, 0 or 1 , preferably all 0, and R3, R3A, R4 and R4A can be identical or different and are each, independently of one another, hydrogen or a C1-C40 radical or two radicals R3A and R4A are joined to one another and together form Q, a divalent organic group having from 1 to 40 carbon atoms.
R3, R3A, R4 and R4A can be identical or different and are each, independently of one another, hydrogen or a C1-C40 radical, for example Ci-C2o-alkyl, C2-C2o-alkenyl, C2-C2o-alkynyl, C5-C4o-aryl, C7-C4o-alkylaryl, C7-C4o-arylalkyl, C2-C4o-heteroaromatic radical, saturated C3-C2o-heterocyclic radical or silyl radical having from 3 to 24 carbon atoms, where the carbon-comprising radical can comprise further heteroatoms selected from the group of elements consisting of F, CI, Br, I, N, P, O and S and/or be substituted by functional groups, or two radicals R3A and R4A are joined to one another and together form Q, a divalent organic group having from 1 to 40 carbon atoms.
Q1, Q2, Q3, Q4 are each, independently of one another, a divalent organic group having from 1 to 40 carbon atoms, where, in addition, two or more substituents on adjacent atoms within Q1, Q2, Q3 and/or Q4 can be joined to one another to form an additional cyclic or polycyclic structure. The divalent organic group having from 1 to 40 carbon atoms can be, for example, a divalent hydrocarbon group, a substituted divalent hydrocarbon group, a divalent heteroatom-com- prising hydrocarbon group, a substituted and at the same time heteroatom-comprising divalent hydrocarbon group or -(CO)-.
The transition metal catalyst complex comprises, beside the transition metal, at least one N-het- erocyclic carbene ligand (NHC-ligand) which is capable of coordinating to the transition metal. The process of the invention is carried out using a transition metal complex in which at least one N-heterocyclic carbene ligand (NHC-ligand) coordinates to the transition metal, for examples carbenes of the formula (l-A) in which w, x, y, z are each 0, p is 1 , q is 1 when Y is N and q is 2 when Y is C,
Y is C or N, preferably N, and two radicals R3A and R4A are joined to one another and together form Q, a divalent organic group having from 1 to 40 carbon atoms.
Further suitable N-heterocyclic carbene ligands, their synthesis and their properties are described in Angew. Chem. 2010, 122, 7094-7107. Suitable heterocyclic carbene ligands are for example represented by the following general structures, wherein R3, R4 or R4A are defined as described above:
Figure imgf000010_0001
Benzimidazol- ylidene
Figure imgf000010_0002
Triazol- Thiazol- Pyrrolidin- ylidene ylidene ylidene
Figure imgf000010_0003
Hexahydro- pyrimidinylidene Perhydro- diazepinylidene
In one embodiment of the present invention, the inventive process is characterized in that the N heterocyclic carbene ligand (NHC-ligand) is selected from imidazol-2-ylidenes, triazol-5-yli- denes, imidazolidine-2-ylidenes, and tetrahydropyrimidin-2-ylidenes, which are substituted or unsubstituted, preferably substituted.
In one embodiment of the present invention, the inventive process is characterized in that the N heterocyclic carbene ligand (NHC-ligand) is defined by general formula (I)
Figure imgf000010_0004
wherein R1 and R2 are independently from each other alkyl, cycloalkyi, heterocycloalkyi, aryl or hetaryl, wherein the alkyl radicals may carry 1 , 2, 3, 4 or 5 substituents selected from cycloalkyi, heterocycloalkyi, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, he- taryloxy, hydroxy, mercapto, polyalkylene oxide, polyalkyleneimine, carboxyl, SO3H, sul- fonate, NE1E2, NE1E2E3+X~, halogen, nitro, formyl, acyl and cyano, wherein E1, E2 and E3 are the same or different and are selected from hydrogen, alkyl, cycloalkyi, and aryl and X" is an anion equivalent,
and wherein the radicals cycloalkyi, heterocycloalkyi, aryl and hetaryl R1 and R2 may carry 1 , 2, 3, 4 or 5 substituents selected from alkyl and the substituents mentioned for the alkyl radicals R1 and R2,
Z is a divalent bridging group selected from -CR3=CR4-, CR3=N-, -CR3R5-CR4R6- and - CR3R5-CR4R6-CR7R8-, wherein R3, R4, R5, R6, R7 and R8 are independently from each other hydrogen or as defined as R1 or two adjacent radicals R3 and R4 and/or R6 and R7 together with the atoms connecting them form a monocyclic or polycyclic, substituted or unsubstituted, aliphatic or aromatic ring system which has from 4 to 40 carbon atoms and can also comprise heteroatoms selected from the group consisting of the elements Si, Ge, N, P, O and S.
In one embodiment of the present invention, the inventive process is characterized in that the N- heterocyclic carbene ligand (NHC-ligand) is selected from the formulas A to I and mixtures thereof
Figure imgf000011_0001
Figure imgf000011_0002
The transition metal complex catalyst of the process of the invention can be employed in the form of a preformed metal complex which comprises a transition metal and at least one
N-heterocyclic carbene ligand (NHC-ligand). Alternatively, the transition metal complex catalyst is formed in situ in the reaction medium by combining a metal compound, herein also termed pre-catalyst, with one or more suitable N-heterocyclic carbene ligand (NHC-ligand) to form a catalytically active metal complex, the transition metal complex catalyst, in the reaction medium. It is also possible that the transition metal complex catalyst is formed in situ in the reaction medium by combining a pre-catalyst with one or more NHC-precursor, in particular the protonated form of a NHC-ligand, which is in situ converted to the corresponding NHC-ligand, to form a catalytically active metal complex in the reaction medium.
In one embodiment of the present invention, the inventive process is characterized in that the N- heterocyclic carbene ligand (NHC-ligand) is prepared in situ by using the corresponding proto- nated form according to formula II,
Figure imgf000012_0001
wherein R1, R2, X" and Z are as defined as described above. Preferably the transition metal complex catalyst is prepared in situ by using the corresponding protonated form according to formula II, a base and a transition metal complex, which does not comprise any heterocyclic carbene ligand.
Suitable bases for deprotonating the protonated form of different NHC ligands according to for- mula II are described by de Fremont et al., Coordination Chemistry Reviews 253 (2009) 876 to 881 . The deprotonation of the protonated forms of NHC ligands can be carried out in ammonia or in non-protic solvents such as THF or ethers. The deprotonation requires anhydrous conditions and the use of strong bases, with pKa values above 14. Usually, potassium or sodium hydride with a catalytic amount of tert-butoxide is employed, but tert-butoxide itself, lithium alumi- num hydride, n-butyllithium, potassium hexamethyldisilazide (KHMDS) and 1 ,8-diazabicy- clo[5.4.0]undec-7-ene (DBU) are also efficient alternatives.
Suitable pre-catalysts are selected from neutral metal complexes, oxides and salts of metals of groups 8, 9 and 10 of the periodic table of the elements. Preferred pre-catalysts are selected from metal complexes, oxides and salts of ruthenium, rhodium, iridium, nickel, platinum or palladium. Ruthenium compounds that are useful as pre-catalyst are, for example, [Ru(methylallyl)2COD], [Ru(p-cymene)CI2]2, [Ru(benzene)CI2]n, [Ru(CO)2CI2]n, [Ru(CO)3CI2]2, [Ru(COD)(allyl)], [RuCly H20], [Ru(acetylacetonate)3], [Ru(DMSO)4CI2], [Ru(PPh3)3(CO)(H)CI], [Ru(PPh3)3(CO)CI2], [Ru(PPh3)3(CO)(H)2], [Ru(PPh3)3CI2], [Ru(Cp)(PPh3)2CI], [Ru(Cp) (CO)2CI], [Ru(Cp)(CO)2H], [Ru(Cp)(CO)2]2, [Ru(Cp*)(CO)2CI], [Ru(Cp*)(CO)2H], [Ru(Cp*)(CO)2]2, [Ru(indenyl)(CO)2CI], [Ru(indenyl)(CO)2H], [Ru(indenyl)(CO)2]2, ruthenocen, [Ru(binap)(CI)2], [Ru(2,2'-bipyridin)2(CI)2- H20], [Ru(COD)(CI)2H]2, [Ru(Cp*)(COD)CI], [Ru3(CO)i2], [Ru(tetraphenylhydroxycyclopentadi- enyl)(CO)2H], [Ru(PMe3)4(H)2], [Ru(PEt3)4(H)2], [Ru(Pn-Pr3)4(H)2], [Ru(Pn-Bu3)4(H)2], [Ru(Pn-oc- tyl3)4(H)2], of which [Ru(methylallyl)2COD], Ru(COD)CI2]2, [Ru(Pn-Bu3)4(H)2], [Ru(Pnoc- tyl3)4(H)2], [Ru(PPh3)3(CO)(H)CI] and [Ru(PPh3)3(CO)(H)2] are preferred, in particular [Ru(meth- ylallyl)2COD].
Iridium compounds that are useful as pre-catalyst are, for example, [lrCI3-H20], KlrCI4, K3lrCl6, [lr(COD)CI]2, [lr(cyclooctene)2CI]2, [lr(ethene)2CI]2, [lr(Cp)CI2]2, [lr(Cp*)CI2]2, [lr(Cp)(CO)2],
[lr(Cp*)(CO)2], [lr(PPh3)2(CO)CI] and [lr(PPh3)3CI], of which [lr(COD)CI]2, [lr(cyclooctene)2CI]2 and [lr(Cp*)CI2]2 are preferred.
Nickel compounds that are useful as pre-catalyst are, for example [Ni(COD)2], Ni(CO)4, NiCI2, NiBr2, Nil2, Ni(OAc)2 [Ni(AcAc)2], [Ni(CI)2(TMEDA)], [Ni(CI)2(DME)], [Ni(Br)2(DME)],
[Ni(CI)2(PPh3)2], [Ni(CO)2(PPh3)], [Ni(CI)(methallyl)]2, [Ni(C03)], nickel(ll)diemthylglyoxime, nickel(ll)2-ethylhexanoate, nickel(ll)hexafluroacetlyacetonate, bis(N,N'-di-t-butylacetamidi- nato)nickel(ll), nickel(ll)oxalate, Ni(N03)2, nickel(ll)stearate, Ni(S04), nickel(ll)tetrafluoroborate hexahydrate, nickel(ll)trifluoroaceylacetonate dehydrate, nickel(ll)trifluoromethanesulfonate. Rhodium compounds that are useful as pre-catalyst are, for example rhodium(ll) salts and rho- dium(lll) salts like rhodium(ll) carboxylate and rhodium(lll) carboxylate, rhodium(ll) acetate and rhodium(lll) acetate, rhodiumbiscarbonylacetylacetonate, acetylacetonatobisethylenerhodium(l) acetylacetonatocyclooctadienylrhodium(l), acetylacetonatonorbornadienylrhodium(l), acetyl- acetonatocarbonyltriphenylphosphinerhodium(l).
Platinum compounds that are useful as pre-catalyst are, for example ammonium tetrachloroplat- inate(ll), bis(tri-t-butylphosphine)platinum (0), bis(ethylenediamine)platinum(ll) chloride, di- bromo(1 ,5-cyclooctadiene)platinum(ll), dichlorobis(benzonitrile)platinum(ll), cis-dichlorobis(di- ethylsulfide)platinum(ll), cis-dichlorobis(pyridine)platinum(ll), cis-dichlorobis(tri- ethylphosphine)platinum(ll), dichloro(1 ,5-cyclooctadiene)platinum(ll), cis-dichlorodiammine plat- inum(ll), di-μ-chloro-dichlorobis(ethylene)diplatinum(ll), dichloro(dicyclopentadienyl)platinum(ll), di-μ-iodobis(ethylenediamine)diplatinum(ll) nitrate, diiodo(1 ,5-cyclooctadiene)platinum(ll), dime- thyl(1 ,5-cyclooctadiene)platinum(ll), platinum(ll) acetylacetonate, platinum(ll) acetylacetonate, platinum(ll) bromide, platinum(ll) chloride, platinum(ll) iodide, potassium bis(oxalato)platinate(ll) dihydrate, tetrakis(triphenylphosphine)platinum(0), tris(dibenzylideneacetone)diplatinum(0). Palladium compounds that are useful as pre-catalyst are, for example allyl(cyclopentadienyl)pal- ladium(ll), bis[(trimethylsilyl)methyl](1 ,5-cyclooctadiene)palladium(ll), allylpalladium chloride di- mer, ammonium tetrachloropalladate(ll), bis[1 ,2-bis(diphenylphosphino)ethane]palladium(0), bis(dibenzylideneacetone)palladium(0), trans-bis(dicyclohexylamine)bis(acetato)palladium(ll), bis(2-methylallyl)palladium chloride dimer, bis(tri-t-butylphosphine)palladium(0), bis(tricyclohex- ylphosphine)palladium(O), bis(tri-o-tolylphosphine)palladium(0), chloromethyl(1 ,5-cyclooctadi- ene)palladium(ll), diacetato[1 ,3-bis(diphenylphosphino)propane]palladium(ll), diacetatobis(tri- phenylphosphine)palladium(ll), diacetato(1 ,10-phenanthroline)palladium(ll), di^-bromobis(tri-t- butylphosphino)dipalladium(l), trans-dibromobis(triphenylphosphine)palladium(ll), dibromo(1 ,5- cyclooctadiene)palladium(ll), dichlorobis(benzonitrile)palladium(ll), dichlorobis(di-t-bu- tylphenylphosphino)palladium(ll), di-μ-chlorobis{2-[(dimethylamino)methyl]phenyl}dipalladium, trans-dichlorobis(tricyclohexylphosphine)palladium(ll), trans-dichlorobis(triphenylphosphine)pal- ladium(ll), dichloro(1 ,5-cyclooctadiene)palladium(ll), dichloro(norbornadiene)palladium(ll), cis- dichloro(N,N,N',N'-tetramethylethylenediamine)palladium(ll), cis-dimethyl(N,N,N',N'-tetrameth- ylethylenediamine)palladium(ll), (l -methylallyl)palladium chloride dimer, palladium(ll) acetate, palladium(ll) acetylacetonate, palladium(ll) benzoate, palladium(ll) bromide, palladium(ll) chloride, palladium(ll) hexafluoroacetylacetonate, palladium(ll) iodide, palladium(ll) sulfate, palla- dium(ll) trifluoroacetate, palladium(ll) trimethylacetate, tetrakis(triphenylphosphine)palladium(0), tris(dibenzylideneacetone)dipalladium(0).
In the aforementioned compound names "COD" denotes 1 ,5-cyclooctadiene; "Cp" denotes cy- clopentadienyl; "Cp*" denotes pentamethylcyclopentadienyl; and "binap" denotes 2,2'-bis(diphe- nylphosphino)-1 ,1 '-binaphthyl. In the process of the invention, a substoichiometric amount of transition metal complex catalyst is generally used, with the amount of transition metal complex catalyst typically being not more than 50 mol%, frequently not more than 20 mol% and in particular not more than 10 mol% or not more than 5 mol%, based on the amount of hydrogenable composition selected from hy- droxymethylfurfural, bishydroxymethylfuran and mixtures thereof. An amount of catalyst of from 0.001 to 50 mol%, frequently from 0.001 mol% to 20 mol% and in particular from 0.005 to
5 mol%, based on the amount of hydrogenable composition selected from hydroxymethylfurfu- ral, bishydroxymethylfuran and mixtures thereof, is generally used in the process of the invention. Preference is given to using an amount of catalyst of from 0.01 to 2 mol% and particularly preferably from 0.01 mol% to 1 mol%. All amounts of transition metal complex catalyst indicated are calculated as transition metal and based on the amount of hydrogenizable composition selected from hydroxymethylfurfural, bishydroxymethylfuran and mixtures thereof.
In one embodiment of the present invention, the inventive process is characterized in that the transition metal complex catalyst is used in an amount of 0.001 mol% to 20 mol%, calculated as transition metal and based on the sum of the amounts of hydroxymethylfurfural and of bishydroxymethylfuran used in the process. The process of the invention is generally carried out at temperatures in the range from -20 °C to 300 °C, preferably in the range from 50 °C to 200 °C and particularly preferably in the range from 80 °C to 180 °C. Temperatures below 150 °C have surprisingly been found to be particularly advantageous.
The process of the invention can be carried out in the presence of a solvent. Suitable solvents are selected from aliphatic hydrocarbons, aromatic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof. Preferred solvents are aliphatic hydrocarbons such as pentane, hexane, heptane, octane or cyclohexane;
aromatic hydrocarbons such as benzene, toluene, xylenes, ethylbenzene, mesitylene or benzotrifluoride;
amides such as dimethylformamide, diethylformamide, /V-methylpyrrolidone, N-ethylpyrrol- idone or dimethylacetamide;
ureas such as tetramethylurea, Ν,Ν-dimethylimidazolinone (DMI) and N,N-dimethylpropyl- eneurea (DMPU);
nitriles such as acetonitrile or propionitrile;
sulfoxides such as dimethyl sulfoxide;
- sulfones such as sulfolane;
alcohols such as methanol, ethanol, propanol or isopropanol;
esters such as methyl acetate, ethyl acetate, f-butyl acetate;
carbonates such as diethyl carbonate, ethylene carbonate and propylene carbonate; ethers such as dioxane, tetrahydrofuran, diethyl ether, dibutyl ether, methyl f-butyl ether, diisopropyl ether or diethylene glycol dimethyl ether; and
water.
If desired, mixtures of two or more of the afore-mentioned solvents can also be used. Preference is given to using aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof as solvents.
In one embodiment of the present invention, the inventive process is characterized in that the reaction is carried out in the presence of a solvent selected from aliphatic hydrocarbons, aro- matic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof.
The hydrogenation can principally be performed according to all processes known to a person skilled in the art which are suitable for the hydrogenation of a HMF-comprising composition. The hydrogen used for the hydrogenation can be used in pure form or, if desired, also in the form of mixtures with other, preferably inert gases, such as nitrogen or argon. Preference is given to using hydrogen in undiluted form. The hydrogenation is typically carried at a hydrogen pressure in the range from 0.1 to 200 bar, preferably in the range from 1 to 50 bar, more preferably in the range from 1 to 15 bar.
The hydrogenation can principally be performed continuously, semi-continuously or discontinu- ously. Preference is given to a continuous process.
The hydrogenation can principally be performed in all reactors known by a person in the art for this type of reaction and therefore, will select the reactors accordingly. Suitable reactors are described and reviewed in the relevant prior art, e.g. appropriate monographs and reference works such as mentioned in US 66391 14 B2, column 16, line 45-49. Preferably, for the hydro- genation an autoclave is employed which may have an internal stirrer and an internal lining.
The composition obtained in the hydrogenation process of the invention comprises cis-(tetrahy- drofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol. In a preferred embodiment according to the invention the obtained composition comprises cis- (tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, wherein the ratio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimethanol is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1 . In one embodiment of the present invention, the inventive process is characterized in that the molar ratio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimetha- nol after finishing the process of hydrogenation is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1 . A further aspect of the invention relates to a composition comprising cis-(tetrahydrofuran-2,5- diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol obtained by the process according to the invention and described above. In particular, the invention relates also to the composition obtained by the process according to the invention and described above comprising cis-(tet- rahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, wherein the ra- tio of cis-(tetrahydrofuran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimethanol is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1.
A further aspect of the invention is the use of a transition metal complex comprising a transition metal and at least one N-heterocyclic carbine ligand (NHC-ligand), which is capable of coordi- nating to the transition metal, such as described above, as hydrogenation catalyst for compositions comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof, wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
A further aspect of the invention is the use of the composition comprising cis-(tetrahydrofuran- 2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, obtained by the process according to the invention and described above for polymerization reactions.
The work-up of the reaction mixture obtained in the hydrogenation of the inventive process and the isolation of cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)di- methanol are effected in a customary manner, for example by filtration, an aqueous extractive work-up or by a distillative separation, for example under reduced pressure. The cis-(tetrahydro- furan-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol may be obtained in sufficient purity by applying such measures or a combination thereof, obviating additional purification steps. Alternatively, further purification can be accomplished by methods commonly used in the art, such as chromatography.
The invention is illustrated by the examples which follow, but these do not restrict the invention. Figures in percent are each based on % by weight, unless explicitly stated otherwise.
Starting Materials
Figure imgf000017_0001
5-Hydroxymethyl-2-furfural (HMF 2,5-Bishydroxymethylfuran
or 5-(hydroxymethyl)furan- (BHMF, furandimethanol or
2-carbaldehyde) furandimethylol)
Figure imgf000017_0002
Tetrahydrofuran-2,5-diyl)- dimethanol
(THF-DM) Pre-catalysts:
Figure imgf000018_0001
Ru(methylallyl)2(COD) RuCI2(COD) Ru(PPh3)3(CO)HCI
Ru(methylallyl)2(COD) is also known as (1 ,5-Cyclooctadiene)bis(2-methylallyl)ruthenium (II). RuC (COD) is also known as (1 ,5-Cyclooctadiene)dichloro-ruthenium (II) and
Ru(PPh3)3(CO)HCI is also known as tris(triphenylphosphine)ruthenium(ll) carbonyl chloride hydride.
NHC-precursors and NHC-ligand:
Figure imgf000018_0002
1 ,3-diisopropyl-4,5-dihydro- 1 ,3-ditertbutyl-4,5-dihydro-
1 ,3-bis(2,6-diisopropylphenyl)-1 H- 1 H-imidazol-3-ium 1 H-imidazol-3-ium imidazol-3-ium chloride
tetrafluoroborate tetrafluoroborate
IPrCI
-BF4
1 ,3-di((3
Figure imgf000018_0003
tetrafluoroborate
L5-BF
-
1 ,3-bi
Figure imgf000018_0004
tetrafluoroborate
L6-BF
Figure imgf000019_0001
1 ,3-bis(2,6-diisopropylphenyl)-1 H- 1 ,3-bis(2,4,6-trimethylphenyl)- imidazolin-3-ium chloride 1 H-imidazol-3-ium chloride
SIPrCI IMesCI
Figure imgf000019_0002
1 ,3-Bis(2,6-diisopropylphenyl)- 1 ,3-dihydro-2H-imidazol-2-ylidene
IPr:
General procedure
Typical screening reactions were done based on a synthetic method described by S. Urban, N. Ortega, F. Glorius, Angew. Chem. Int. Ed. 201 1 , 50, 3803-3806.
In a glove box, [Ru(cod)(2-methylallyl)2] (1 1 mg, 0.036 mmol, 4.5 mol%), imidazolium salt (0.071 mmol, 9 mol%), and anhydrous KOtBu (12 mg, 0.107 mmol, 13.5 mol%)* were added to a micro-wave vial equipped with a magnetic stir bar. The mixture was suspended in toluene (2 mL) and stirred at 50 °C overnight. Then the vessel was opened in a glovebox, and a further 8 mL of toluene and the HMF (100 mg, 0,79 mmol, 1 equivalent) were added. The vial was stirred or sonicated until full dissolution of the HMF and the solution was transferred to an N2 purged glass autoclave, under a flow of N2. The autoclave was tightly closed, purged with N2 then H2 (typically, 3 times each, 5 bars), and finally pressurized with H2 to the desired pressure. An oil bath was used to bring the autoclave to the desired temperature (at 120°C, unless specified otherwise), and was stirred for the specified duration (typically overnight). A sample was collected (while the autoclave was still at the indicated temperature), the solvent was removed in vacuo, the resulting oil was dissolved in D6-DMSO and analyzed by NMR. The ratio of HMF : BHMF : THF-DM was determined by 1H NMR, and the ratio of cis : trans THF-DM was determined by integration of the relevant carbon peaks by 13C NMR, as described in the literature (based on an analytic method described by G. Bottari, A. J. Kumalaputri, K. K. Krawczyk, B. L. Feringa,H. J. Heeres, K. Barta, ChemSusChem 2015, 8, 1323 - 1327).
*: nb. When using the free carbene, the pre-existing ylidene was used instead of the imidazolium salt, and no base was employed. Results
Table 1 summarizes the result of the different hydrogenation experiments. In each case the re- suit of the hydrogenation is reported as a ratio of the starting material (HMF), the intermediate (BHMF) and the desired product (THF-glycol). The amount of BHMF is normalized to 1 to facilitate comparison of the results.
Table 1
Ligand (X mol%)
Entry Metal (Y mol%) HMF BHMF THF-DM cis : trans
KOtBu (Z mol%)
IPrCI (9%)
1 Ru(methylallyl)2(COD) (4.5%) 0.07 0.4 1 .26:1
KOfBu (13.5%)
IPrCI (9%)
2 Ru(PPh3)3(CO)HCI (4.5%) 0.01 1 .7 1 .88:1
KOfBu (13.5%)
IPrCI (5%)
3 Ru(PPh3)3(CO)HCI (2.5%) 0.02 - - KOfBu (7%)
IPrCI (9%)
4 RuC (COD) (4.5%) 0.03 0.04 5.18:1
KOfBu (13.5%)
IPrCI (5%)
5 RuC (COD) (2.5%) 0.03 0.02 - KOfBu (7%)
Figure imgf000020_0001
6 Ru(methylallyl)2(COD) (4.5%) 0.02 <0.05 4.6:1
KOfBu (13.5%)
Figure imgf000020_0002
7 Ru(methylallyl)2(COD) (4.5%) 0.01 0.18 3.3:1
KOfBu (13.5%)
Figure imgf000020_0003
8 Ru(methylallyl)2(COD) (4.5%) 0.05 <0.05 3.18:1
KOfBu (13.5%)
Figure imgf000020_0004
9 Ru(methylallyl)2(COD) (4.5%) 0.01 <0.05 1 .6:1
1
KOfBu (13.5%) Ligand (X mol%)
Entry Metal (Y mol%) HMF BHMF THF-DM cis : trans
KOtBu (Z mol%)
L5-BF4 (9%)
10 Ru(methylallyl)2(COD) (4.5%) 0.02 1 1 .65 2.8:1
KOfBu (13.5%)
Figure imgf000021_0001
1 1 Ru(methylallyl)2(COD) (4.5%) - 1 3.2 3.95:1
KOfBu (13.5%)
SIPrCI (6%)
12 Ru(methylallyl)2(COD) (2.5%) - 1 0.09 2.3:1
KOfBu (6%)
IPrCI (6%)
Ru(methylallyl)2(COD) (2.5%)
13 0.02 1 3.2 3.8:1
KOfBu (6%)
At 130°C
IPrCI (6%)
Ru(methylallyl)2(COD) (2.5%)
14 0.02 1 1 .54 3.8:1
KOfBu (6%)
At 140°C

Claims

Claims
A process for the hydrogenation of a composition comprising hydroxymethylfurfural, bishydroxymethylfuran or mixtures thereof to obtain a composition comprising cis-(tetrahy- drofuran-2,5-diyl)dimethanol and trans-(tetrahydrofuran-2,5-diyl)dimethanol, which process comprises reacting the composition comprising hydroxymethylfurfural,
bishydroxymethylfuran or mixtures thereof with hydrogen in a liquid reaction medium comprising a transition metal complex catalyst in homogeneous solution, wherein the transition metal complex catalyst comprises a transition metal and at least one N-heterocyclic carbene ligand (NHC-ligand) which is capable of coordinating to the transition metal and wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
The process according to claim 1 , wherein the transition metal is selected from the group consisting of ruthenium, rhodium, iridium, nickel, platinum and palladium.
The process according to claim 1 or 2, wherein the N-heterocyclic carbene ligand (NHC- ligand) is selected from imidazol-2-ylidenes, triazol-5-ylidenes, imidazolidine-2-ylidenes, and tetrahydropyrimidin-2-ylidenes, which are substituted or unsubstituted, preferably substituted.
The process according to any of claims 1 to 3, wherein the N-heterocyclic carbene ligand (NHC-ligand) is defined by general formula (I)
Figure imgf000022_0001
R1 and R2 are independently from each other alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, wherein the alkyl radicals may carry 1 , 2, 3, 4 or 5 substituents selected from cycloalkyl, heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloal- koxy, aryloxy, hetaryloxy, hydroxy, mercapto, polyalkylene oxide, polyalkyleneimine, carboxyl, SO3H, sulfonate, NE1E2, NE1E2E3+X~, halogen, nitro, formyl, acyl and cy- ano, wherein E1, E2 and E3 are the same or different and are selected from hydrogen, alkyl, cycloalkyl, and aryl and X" is an anion equivalent,
and wherein the radicals cycloalkyl, heterocycloalkyl, aryl and hetaryl R1 and R2 may carry 1 , 2, 3, 4 or 5 substituents selected from alkyl and the substituents mentioned for the alkyl radicals R1 and R2, Z is a divalent bridging group selected from -CR3=CR4-, CR3=N-, -CR3R5-CR4R6- and - CR3R5-CR4R6-CR7R8-, wherein R3, R4, R5, R6, R7 and R8 are independently from each other hydrogen or as defined as R1 or two adjacent radicals R3 and R4 and/or R6 and R7 together with the atoms connecting them form a monocyclic or polycyclic, substituted or unsubstituted, aliphatic or aromatic ring system which has from 4 to 40 carbon atoms and can also comprise heteroatoms selected from the group consisting of the elements Si, Ge, N, P, O and S.
The process according to any of claims 1 to 4, where the N-heterocyclic carbene ligand (NHC-ligand) is selected from the formulas A to I and mixtures thereof
Figure imgf000023_0001
The process according to claim 4, where the N-heterocyclic carbene ligand (NHC-ligand) is prepared in situ by using the corresponding protonated form according to formula II
Figure imgf000023_0002
wherein R1, R2, X" and Z are as defined as in claim 4.
The process according to claim 6, where the transition metal complex catalyst is prepared in situ by using the corresponding protonated form according to formula II, a base and a - transition metal complex, which does not comprise any heterocyclic carbene ligand.
The process according to any of claims 1 to 7, wherein the transition metal complex catalyst is used in an amount of 0.001 mol% to 20 mol%, calculated as transition metal and based on the sum of the amounts of hydroxymethylfurfural and of bishydroxymethylfuran used in the process.
The process according to any of claims 1 to 8, wherein the reaction is carried out in the presence of a solvent selected from aliphatic hydrocarbons, aromatic hydrocarbons, amides, ureas, nitriles, sulfoxides, sulfones, alcohols, esters, carbonates, ethers, water and mixtures thereof.
The process according to any of claims 1 to 9, wherein the molar ratio of cis-(tetrahydrofu ran-2,5-diyl)dimethanol to trans-(tetrahydrofuran-2,5-diyl)dimethanol after finishing the process of hydrogenation is in the range of 7:1 to 1 :1 , preferably in the range of 5:1 to 1 :1 A composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tetrahydrofu- ran-2,5-diyl)dimethanol obtained by the process of any of claims 1 to 10.
Use of a transition metal complex comprising a transition metal and at least one N-hetero- cyclic carbine ligand (NHC-ligand), which is capable of coordinating to the transition metal, as hydrogenation catalyst for compositions comprising hydroxymethylfurfural,
bishydroxymethylfuran or mixtures thereof, wherein the transition metal is selected from metals of groups 8, 9 and 10 of the periodic table of the elements according to lUPAC.
Use of the composition comprising cis-(tetrahydrofuran-2,5-diyl)dimethanol and trans-(tet- rahydrofuran-2,5-diyl)dimethanol according to claim 1 1 for polymerization reactions.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975532A (en) * 1973-06-14 1976-08-17 Ici United States Inc. Hexahydro-1H-furo(3,4-c) pyrrole compounds for treating pain
US6639114B2 (en) 2001-02-13 2003-10-28 Basf Aktiengesellschaft Hydroformylation catalyst comprising a complex with ligands having a structure derived from bisphenol A
US20070287845A1 (en) 2006-06-09 2007-12-13 Battelle Memorial Institute Hydroxymethylfurfural Reduction Methods and Methods of Producing Furandimethanol
WO2014200636A1 (en) * 2013-06-12 2014-12-18 Archer Daniels Midland Company Synthesis of dicarbamates from reduction products of 2-hydroxymethyl-5-furufural (hmf) and derivatives thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975532A (en) * 1973-06-14 1976-08-17 Ici United States Inc. Hexahydro-1H-furo(3,4-c) pyrrole compounds for treating pain
US6639114B2 (en) 2001-02-13 2003-10-28 Basf Aktiengesellschaft Hydroformylation catalyst comprising a complex with ligands having a structure derived from bisphenol A
US20070287845A1 (en) 2006-06-09 2007-12-13 Battelle Memorial Institute Hydroxymethylfurfural Reduction Methods and Methods of Producing Furandimethanol
WO2014200636A1 (en) * 2013-06-12 2014-12-18 Archer Daniels Midland Company Synthesis of dicarbamates from reduction products of 2-hydroxymethyl-5-furufural (hmf) and derivatives thereof

Non-Patent Citations (9)

* Cited by examiner, † Cited by third party
Title
ANGEW. CHEM., vol. 122, 2010, pages 7094 - 7107
CONNOLLY ET AL., ORGANIC PROCESS RESEARCH & DEVELOPMENT, vol. 14, 2010, pages 459 - 465
DE FREMONT ET AL., COORDINATION CHEMISTRY REVIEWS, vol. 253, 2009, pages 876 - 881
G. BOTTARI; A. J. KUMALAPUTRI; K. K. KRAWCZYK; B. L. FERINGA; H. J. HEERES; K. BARTA, CHEMSUSCHEM, vol. 8, 2015, pages 1323 - 1327
N. ORTEGA ET. AL.: "Ruthenium NHC Catalyzed Highly Asymmetric Hydrogenation of Benzofurans", ANGEWANDTE COMMUNICATIONS, vol. 51, 17 September 2012 (2012-09-17), pages 1710 - 1713, XP055025995 *
RAUCHFUSS ET AL., CHEMSUSCHEM, vol. 3, 2010, pages 1139 - 1141
S. URBAN; N. ORTEGA; F. GLORIUS, ANGEW. CHEM. INT. ED., vol. 50, 2011, pages 3803 - 3806
T. DRÖGE ET. AL.: "Das Mass aller Ringe- N-heterocyclische Carbene", ANGEWANDTE CHEMIE, vol. 122, 17 September 2010 (2010-09-17), pages 7094 - 7107, XP002772207 *
T. J. CONNOLLY ET. AL.: "Efficient Synthesis of 8-Oxa-3-aza-bicyclo[3.2.1]octane Hydrochloride", ORGANIC PROCESS RESEARCH AND DEVELOPMENT, vol. 14, 16 February 2010 (2010-02-16), pages 459 - 465, XP002772206, DOI: 10.1021/op9002642 *

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