Process for preparation of acetal protected sugars

Abstract

Process for the preparation of acetal-protected sugars comprising the step of reacting a diol group of a sugar selected from the group consisting of valeralose and hexaldehyde with one or both compounds of formula (Ia) and / or formula (Ib) in the presence of a homogeneous or heterogeneous catalyst, to form an acetal protected sugar selected from the group consisting of compounds of formula (II), formula (III) and formula (IV); wherein R1 and / or R2 are each independently-Z-X, and wherein Z is a linear, branched or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, optionally substituted by 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, or Z is-B-D, where B is a linear hydrocarbon moiety having 1 to 3 carbon atoms and may be present or absent, D is an aromatic moiety having 6 carbon atoms, wherein Z may be present or absent, and X is-COOH,-CH (COOH) 2,-COOR3, CHO,-C2H3,-C2H,-CHOR4OR5,-N3,-NHR6,-NR7R8,-F,-Cl,-Br,-I, or, if Z is present, X is-OH, NH2, or-SH, optionally substituted by 1 to 4 C1-C4 alkyl groups, 1 to 2-OH groups, 1 to 2-OCH3 groups, or 1 to 4 halogen atoms, and wherein Z may be present or absent,-COOR3, CHO,-C2H3,-C2H,-CHOR4OR5,-N3,-NHR6,-NR7R8,-F,-Cl,-Br,-I; r3, R4 and R5 are independently selected from the group consisting of linear, branched or cyclic hydrocarbon moieties having 1 to 20 carbon atoms and optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms selected from the group consisting of fluorine, chlorine, bromine and iodine; r6 is a C1-C4 alkyl group; r7, R8 and R9 are each independently a C1-C4 alkyl group; r30 and R31 are each independently selected from the group consisting of hydrogen and a linear or branched hydrocarbon moiety having 1 to 4 carbon atoms, with the proviso that R30 and R31 cannot be hydrogen at the same time; r < 10 > is selected from the group consisting of-H,-OH,-CH2OH,-OR13 or-CH2OR14; r < 11 > and R < 12 > are independently selected from the group consisting of-OH or-OR13; r13 and R14 are independently selected from hydrocarbon moieties having from 1 to 10 carbon atoms; and n and p are each independently 0 or 1.

Description

Technical Field

[0001] This invention relates to a method for preparing acetal-protected sugars. A method for preparing acetal-protected lignin fragments is further disclosed. Background Technology

[0002] Plastic materials such as polyethylene terephthalate (PET) or polypropylene (PP) are widely used. However, plastic pollution has become one of the most pressing environmental problems because the production of single-use plastic products has increased rapidly, exceeding the world's capacity to process them. Therefore, new materials that can potentially replace traditional plastic materials are being researched.

[0003] Lignin is reportedly the second most abundant natural polymer on Earth after cellulose, accounting for 15-30 wt% of lignocellulosic biomass. Unlike cellulose and hemicellulose, the other two main components of lignocellulosic biomass, lignin is not a polysaccharide. Instead, lignin is said to contain a large number of aromatic subunits. This structure gives lignin a 30% higher energy density than cellulose polymers and makes it one of the few natural sources of aromatic molecules. Due to these properties, lignin monomers are increasingly considered important precursors for many different applications.

[0004] WO2017178513A1 discloses a pretreatment method for lignocellulose biomass that yields high lignin monomer yields. The method involves heating a lignocellulose composition with an aldehyde, ketone, boric acid, or a compound selected from 2-methoxypropylene, dimethyl carbonate, and 2,2-dimethoxypropane under acidic conditions. Formaldehyde is a preferred protective agent, but it presents safety concerns when scaled up to large-scale operations. Alternatively, glyoxylic acid (GA) can be used as a safer, potentially bio-based, alternative aldehyde, but it is relatively expensive, viscous, and difficult to recycle.

[0005] Digyloxylic acid xylose (DGAX) and its corresponding esters (such as dimethylglyoxylate xylose (DMGX)) can be used to produce a new class of polyesters, namely poly(alkylene xylose diglyoxylate) (PAX), which have properties similar to poly(ethylene terephthalate) (PET), but are bio-based and can be readily chemically recycled, eventually degrading back to sugar in the presence of water. Furthermore, this diacid / diester can be used directly in a wide variety of other applications (e.g., adhesives, surfactants, etc.) or as a platform molecule for the synthesis of acetal-stabilized xyloses with other functional groups (e.g., diols, diamines, etc.).

[0006] However, currently, DGAX / DMGX is synthesized in a high-viscosity reaction mixture using the homogeneous synthesis method disclosed in EP 4045514 A1, and requires a large excess of glyoxylic acid, which is expensive and very difficult to recover. Furthermore, the corrosive nature and limited stability of glyoxylic acid necessitate careful handling and storage conditions. As a result, scaling up this process will lead to high operating costs as well as increased equipment and maintenance costs. Moreover, the use of glyoxylic acid significantly increases the viscosity of the reaction mixture compared to formaldehyde, thus potentially requiring significant capital expenditure for high-torque reactor systems. Summary of the Invention

[0007] The problem of this invention is to provide a method for preparing acetal-protected sugars that is more environmentally friendly, cost-effective, and easily scalable. Detailed Implementation

[0008] This problem is solved by the method for preparing acetal-protected sugars according to claim 1. Further preferred embodiments are the subject of the dependent claims.

[0009] This invention relates to a method for preparing acetal-protected sugars, comprising the steps of: reacting a diol group of a sugar selected from the group consisting of pentaldehydes and hexaldehydes with one or both compounds of formula (Ia) and / or formula (Ib) in the presence of a homogeneous or heterogeneous catalyst.

[0010]

[0011] To form sugars protected by acetals selected from the group consisting of compounds of formula (II), (III) and (IV),

[0012]

[0013]

[0014]

[0015] Where R1 and / or R2 are each independent and are -ZX, and

[0016] in

[0017] Z is a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, or Z is -BD, wherein

[0018] B is a straight-chain hydrocarbon moiety with 1 to 3 carbon atoms, and may or may not be present.

[0019] D is an aromatic moiety having 6 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups, 1 to 2 -OH groups, 1 to 2 -OCH3 groups, or 1 to 4 halogen atoms and combinations thereof, wherein

[0020] Z may or may not exist, and

[0021] X is -COOH, -CH(COOH)2, -COOR3, CHO, -C2H3, -C2H, -CHOR4OR5, -N3, -NHR6, -NR7R8, -F, -Cl, -Br, -I, or if Z is present, X is -OH, NH2, or -SH;

[0022] R3, R4 and R5 are each independently selected from and are straight-chain, branched or cyclic hydrocarbon moieties having 1 to 20 carbon atoms, optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms selected from the group consisting of fluorine, chlorine and bromine and iodine.

[0023] R6 is a C1-C4 alkyl group;

[0024] R7 and R8 are each independently selected from and are C1-C4 alkyl groups;

[0025] R 30 and R 31 Each is independently selected from the group consisting of hydrogen and a straight-chain or branched hydrocarbon moiety having 1 to 4 carbon atoms, provided that R 30 and R 31 It cannot be hydrogen at the same time;

[0026] R 10 Selected from -H, -OH, -CH2OH, -OR 13 or -CH2OR 14 The group formed;

[0027] R 11 and R 12 Independently selected from -OH or -OR 15 The group formed;

[0028] R 13 R 14 and R 15 Independently selected from hydrocarbon moieties having 1 to 10 carbon atoms; and

[0029] n and p are each independently 0 or 1.

[0030] For chemical moieties, such as alkyl, aromatic, or aliphatic moieties, they are substituted, meaning one of the hydrogen atoms in the moiety is replaced by a substituent. For example, the -C6H5 moieties substituted with methyl groups correspond to the -C6H4(CH3) moieties.

[0031] The term "a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 20 carbon atoms, optionally substituted with 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms" refers to a straight-chain, branched, or cyclic hydrocarbon chain containing 1 to 20 carbon atoms. Examples of this term, as used herein, include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, fluoromethyl, difluoromethyl, trifluoromethyl, fluoroethyl, difluoroethyl, 1-fluoroisopropyl, 1,1-difluoroisopropyl, 1,1,1-trifluoroisopropyl, 1,1,1,2-tetrafluoroisopropyl, pentafluoroisopropyl, hexafluoroisopropyl, hexyl, etc.

[0032] The term "aromatic moiety having 6 carbon atoms, optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms" describes an aromatic ring structure containing 6 carbon atoms. Examples of this term, as used herein, include phenyl, benzyl (where B is CH2), and tolyl.

[0033] The method for preparing acetal-protected sugars according to the present invention has the following advantages: acetal-protected sugars are obtained using acetal compounds of formula (Ia) and / or formula (Ib) as protecting agents. By using acetals as reagents and in excess, the viscosity of the acetal-protected sugars is reduced. This reduction in viscosity improves the scalability of the production method, which significantly reduces capital costs.

[0034]

[0035] Another advantage of the method of the present invention is that by using acetal as a reagent, the reactivity of common undesirable side reactions of aldehydes and ketones (such as aldol condensation) is significantly reduced.

[0036] Furthermore, the production method according to the invention is not limited to a specific type of catalyst, as the reaction can be catalyzed by homogeneous or heterogeneous catalysis.

[0037] Furthermore, by utilizing the esterified form of glyoxylic acid (here, compounds (Ia) and / or (Ib)), xylose diglyoxylate can be produced from D-xylose in a single step, instead of the two steps disclosed in WO 2021074211 A1. This reduces costs compared to prior art synthesis.

[0038] Another advantage of the production method according to the invention is that the prepared tricyclic compound is very stable and can be easily separated and purified. Furthermore, the tricyclic compound can be used as a building block for polymers with higher glass transition temperatures compared to most other monomers mentioned in the prior art. For example, polyesters produced from DMGX and 1,2-ethylene glycol have a glass transition temperature of 137°C, while polymers produced from the same glycol and commercial terephthalic acid have only a glass transition temperature of 60-75°C.

[0039] Replacing formaldehyde with glyoxylic acid as a protective agent increases production costs, product viscosity, and reduces recyclability. On the other hand, using the acetal form of glyoxylic acid esters (e.g., ethyl diethoxyacetate (EDEA)) reduces the viscosity of the reaction product. Furthermore, using the acetalized form of glyoxylic acid (e.g., EDEA) has the advantage that the protective agent can usually be purchased in pure form, rather than as a monohydrate or aqueous solution as in the case of glyoxylic acid. This avoids the need for expensive drying steps. Secondly, reaction byproducts (e.g., in the DGAX synthesis) are converted into alcohols (e.g., methanol or ethanol), which are much easier to remove from the reaction mixture than water.

[0040] Preferably, the method for preparing acetal-protected sugars includes the following steps: heating a mixture of diol groups of the sugar to a temperature between 50°C and 150°C in the presence of a homogeneous catalyst or a heterogeneous catalyst, more preferably to a temperature between 70°C and 110°C, and most preferably to a temperature between 80°C and 100°C.

[0041] In a preferred embodiment of the method for preparing acetal-protected sugars, the heating of the mixture of diol groups of the sugar in the presence of a homogeneous or heterogeneous catalyst is carried out under reduced pressure between 20 mbar and 450 mbar, more preferably between 50 mbar and 100 mbar.

[0042] Preferably, the method for preparing acetal-protected sugars includes the following steps: heating a mixture of diol groups of sugars under reduced pressure for 1 to 10 hours, more preferably 3 to 8 hours, in the presence of a homogeneous or heterogeneous catalyst.

[0043] In a preferred embodiment of the method for preparing acetal-protected sugars, -ZX is selected from the group consisting of: -PhCOOH, -CH2-Ph-COOH,

[0044] -CH2-CH2-Ph-COOH, -CH2-CH2-CH2-Ph-COOH, -CH=CH-CH2-Ph-COOH, -CH2-CH=CH-Ph-COOH,

[0045] -CH(COOH)2、-COOMe、-CH2COOMe、-CH2-CH2-COOMe、-Ph-COOMe、

[0046] -CH(COOMe)2, -C6H 10 -COOMe,

[0047] -COOEt、-CH2COOEt、-CH2CH2COOEt、-Ph-COOEt、-CH(COOEt)2、-C6H 10 -COOEt,

[0048] -CH2-CH2-CHO, -CH2-CH2-CH2-CHO, -CH=CH-CH2-CHO, -CH2-CH=CH-CHO,

[0049] -Ph-CHO, -C6H 10 -GIVE,

[0050] -CHCH2、-CH2CHCH2、-CH2CH2CHCH2、-Ph-CHCH2、-C6H 10 CHCH2, -CH2CCH,

[0051] -CH2CH2CCH, -Ph-CCH, -C6H 10 -CCH、-CH2N3、-CH2CH2N3、-Ph-N3、

[0052] -C6H 10 -N3、-CH2NH2、-CH2CH2NH2、-Ph-NH2、-C6H 10 -NH2,

[0053] -CH2SH、-CH2CH2SH、-Ph-SH、-C6H 10 -SH,

[0054] -NH-CH3, -CH2-NH-CH3, -CH2CH2-NH-CH3, -Ph-NH-CH3, -C6H 10 -NH-CH3,

[0055] -CH2OH、-CH2CH2OH、-Ph-OH、-C6H 10 -OH

[0056] -CH2F、-CH2CH2F、-CH2CH2CH2F、-Ph-F、-C6H 10 F

[0057] -CH2Cl, -CH2CH2Cl, -CH2CH2CH2Cl, -Ph-Cl, -C6H 10 -Cl、

[0058] -CH2Br, -CH2CH2Br, -CH2CH2CH2Br, -Ph-Br, -C6H 10 -Br and

[0059] -CH2I, -CH2CH2I, -CH2CH2CH2I, -Ph-I, -C6H 10 -I,

[0060] Me represents methyl, Et represents ethyl, and Ph represents benzene ring.

[0061] One embodiment of the present invention relates to a method in which R1 and / or R2 are each independently -ZX, and wherein

[0062] Z is a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, or Z is -BD, wherein

[0063] B is a straight-chain hydrocarbon moiety with 1 to 3 carbon atoms, and may or may not be present.

[0064] D is an aromatic moiety having 6 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups, 1 to 2 -OH groups, 1 to 2 -OCH3 groups, or 1 to 4 halogen atoms and combinations thereof, wherein

[0065] Z may or may not exist, and

[0066] X is -CH(COOH)2, -COOR3, CHO, -C2H3, -C2H, -CHOR4OR5, -N3, -NHR6, -NR7R8, -F, -Cl, -Br, -I, or if Z is present, X is -COOH, -OH, NH2, or -SH; and preferably if Z is a straight-chain, branched, or cyclic hydrocarbon moiety, X is not -COOH.

[0067] In a preferred embodiment of the method for preparing acetal-protected sugars, the reaction is carried out under solvent-free conditions. The term "solvent-free conditions" means that no additional solvent is used in the reaction mixture besides the starting materials. In the context of this invention, a solvent is a substance with the ability to dissolve the starting materials to form a homogeneous mixture. Reactions under solvent-free conditions have the advantages of eliminating the need to remove the solvent from the reaction products and preventing cross-reactions between the starting materials and the solvent that could lead to unwanted byproducts. Furthermore, the absence of a solvent eliminates the need for solvent recovery, making the production of acetal-protected sugars more environmentally friendly. Finally, the ability to conduct the reaction under solvent-free conditions results in high product concentrations in the effluent, significantly reducing process volume and increasing overall productivity.

[0068] In another embodiment of the method for preparing acetal-protected sugars, the reaction is carried out in a solvent, more preferably in a solvent selected from the group consisting of: dimethyl isosorbide; cyclic ethers, particularly 1,4-dioxane or 2-methyltetrahydrofuran; sulfolane, sulfolane; aliphatic acids, particularly acetic acid; alkylpyrrolidones, cyclic carbonates; cyclic esters, particularly γ-valerolactone or γ-butyrolactone; acetonitrile; and non-cyclic ethers, particularly diethyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, triethylene glycol monoether / triethylene glycol diether. These solvents have the advantage that they can be easily removed while allowing for high conversion of the sugar to be protected.

[0069] In a preferred embodiment of the method for preparing acetal-protected sugars, unreacted compounds of formula (Ia) and / or formula (Ib) can be recycled to reduce production costs.

[0070] In a further preferred embodiment of the method for preparing acetal-protected sugars, unreacted compounds of formula (Ia) and / or formula (Ib) are recovered by distillation. The advantage of recovering unreacted compounds of formula (Ia) and / or formula (Ib) by distillation is that they can be recovered using a mild separation process that does not interfere with the chemical structure of the compounds of formula (Ia) and / or formula (Ib), and can be reused in subsequent processes.

[0071] In a preferred embodiment of the method for preparing acetal-protected sugars, Z is absent in R1 and / or R2 of compounds (Ia) and (Ib). In the context of this invention, the term "absent" refers to compounds (Ia) and (Ib) in which X is directly attached to R in the residual groups R1 and / or R2. 31 -O-CH-OR 30 On the carbon atoms of the skeleton. In this specific embodiment, compounds (Ia) and (Ib) have the following formula:

[0072] .

[0073] When Z is absent, the proximity of the functional group to the electrophilic acetal can increase the reactivity of the attached functional group during subsequent polymerization. For example, when X in (Ia) / (Ib) is COOR3, the electron-withdrawing effect of the acetal increases the electrophilicity of the carbonyl group, making it more susceptible to nucleophilic attack. Furthermore, if (Ia) and (Ib) are fossil-derived, this also enables the production of bifunctional molecules from renewable sugars with minimal fossil-based carbon incorporation.

[0074] In a preferred embodiment of the method for preparing acetal-protected sugars, R 30 and R 31 They are the same. Where R... 30 and R 31 The use of the same acetal compounds according to formulas (Ia) and / or (Ib) has the advantage that these acetal compounds are easier to synthesize and produce significantly fewer byproducts in the production reaction that forms acetal-protected sugars. Wherein R 30 and R 31 The same reagent ratio of R 30 and R 31 The different ones are much easier to produce. This promises to lead to more economical processes.

[0075] In a preferred embodiment of the method for preparing acetal-protected sugars, in R1 and / or R2, Z is -CH2 or absent, X is a halogen selected from the group consisting of Cl and Br or -COOR3, and R3 is -CH3 or -CH2CH3. More preferably, R1 and / or R2 are selected from the group consisting of -CH2-COOCH3, -CH2-COOCH2CH3, -COOCH3, CH2Cl, CH2Br, and -COOCH2CH3.

[0076] In a preferred embodiment of the method for preparing acetal-protected sugars, R 30 R 31 It is the same as R3. More preferably, compound (Ia) and / or compound (Ib) are selected from the group consisting of:

[0077]

[0078] Further good results can be obtained by using the following halogenated acetals:

[0079]

[0080] As mentioned above, replacing formaldehyde with glyoxylic acid as a protective agent increases cost, viscosity, and makes recovery more difficult. Using the acetal form of glyoxylic acid esters (called ethyl acetate diethoxylate (EDEA)) reduces the viscosity of the reaction products. Furthermore, by using the acetalized form of glyoxylic acid (e.g., EDEA), it is advantageous that the protective agent can generally be purchased in pure form, rather than as a monohydrate or aqueous solution as in the case of glyoxylic acid. This avoids the need for expensive drying steps. Secondly, reaction byproducts (e.g., in the DGAX synthesis) are converted to alcohols (e.g., methanol or ethanol), which are far easier to remove from the reaction mixture than water. The presence of the linking group -Z produces a polymer precursor with enhanced flexibility due to the additional carbon spacing between the acetal and the functional group.

[0081] In a preferred embodiment of the method for preparing acetal-protected sugars, compounds (Ia) and / or compounds (Ib) are selected from the group consisting of:

[0082]

[0083]

[0084]

[0085] These molecules are all available on an industrial scale and are leading candidates for the production of DGAX esters or slightly modified DGAX esters (with an extra carbon to increase flexibility). These molecules can be used to produce high-performance polymers.

[0086] A more preferred embodiment of the present invention relates to a method for preparing compound (II),

[0087] ,

[0088] Where R 10 R 11 As defined above, and R1 and R2 are selected from the group consisting of -COOR3, -CH2COOR3, and -CH2OH, where R3 is as defined above. Surprisingly, when compound (II), in which R1 and R2 are -COOR3 and R3 is a methyl group, is incorporated into a polyester, the compound possesses properties that impart performance. This compound is polymerized with a series of diols to produce a series of polyesters, hereinafter referred to as poly(alkylene xylose diglyoxylate) (PAX). These polyesters exhibit strong, stiff, and tough mechanical properties, high glass transition temperatures, and good gas barrier properties, making them potential alternatives to poly(ethylene terephthalate) (PET). Notably, they can be chemically recycled under extremely mild conditions and are degradable in water at room temperature.

[0089] Furthermore, it was surprisingly shown that the acetal-protected sugar of compound (II) in which R1 and R2 are -CH2COOR3 has enhanced flexibility due to the extra carbon compared to compound (II) in which R1 and R2 are -COOR3.

[0090] Preferred embodiments of the present invention relate to methods for preparing compound (III) or compound (IV).

[0091]

[0092] ,

[0093] Where R1, R2, R 10 R 11 R 12 n and p are defined as above.

[0094] A more preferred embodiment of the present invention relates to a method for preparing compound (III) or compound (IV).

[0095]

[0096] ,

[0097] Where R 10 R 11 R 12 , n, and p are as defined above, and R1 and R2 are selected from the group consisting of -COOR3, -CH2COOR3, and -CH2OH, wherein R3 is as defined above. Surprisingly, the acetal-protected sugars of compounds (III) or (IV) wherein R1 and R2 are selected from the group consisting of -COOR3 and -CH2OH result in polymers with excellent properties, as described above for compound (II). Therefore, such compounds (III) or (IV) are preferred for the production of high-performance materials that require, for example, mechanical resistance, thermal stability, or the ability to act as gas barriers. Furthermore, surprisingly, the acetal-protected sugars of compounds (III) or (IV) wherein R1 and R2 are -CH2COOR3 have enhanced flexibility due to the additional carbon compared to compounds (II) wherein R1 and R2 are -COOR3.

[0098] In a preferred embodiment of the method for preparing acetal-protected sugars, the catalyst is a homogeneous catalyst. More preferably, the homogeneous catalyst is an organic or inorganic acid, most preferably selected from the group consisting of H₂SO₄, H₃PO₄, HBr, HCl, FeCl₃, AlCl₃, TiCl₄, RuCl₃, SnCl₄, phosphotungstic acid, phosphomolybdic acid, tungstic silicic acid, methanesulfonic acid, and p-toluenesulfonic acid. These catalysts can be obtained on an industrial scale at a relatively low cost. Furthermore, large-scale processing of most of these molecules is well-established.

[0099] In a preferred embodiment of the method for preparing acetal-protected sugars, the catalyst is a heterogeneous catalyst. Preferably, the heterogeneous catalyst is a heterogeneous acidic catalyst; more preferably, the heterogeneous catalyst is a Brønsted acidic catalyst; most preferably, the heterogeneous catalyst is selected from the group consisting of acidic zeolite, acidic doped zeolite, acid site-functionalized resin, acid site-functionalized oxide, acid oxide, and immobilized homogeneous acid, wherein the homogeneous acid is selected from the group consisting of H2SO4, H3PO4, phosphotungstic acid, phosphomolybdic acid, tungstic silicic acid, methanesulfonic acid, silica sulfuric acid, and p-toluenesulfonic acid.

[0100] As used herein, the term "acidic site functionalized resin" refers to a resin or polymer synthesized from an organic polymer substrate that acts as an ion exchange medium. This organic polymer substrate is, for example, sulfonated polystyrene-divinylbenzene or a fluoropolymer-polymer copolymer based on sulfonated tetrafluoroethylene, resulting in a strongly acidic cation exchange resin or polymer. Non-limiting examples include Amberlyst-15, Amberlyst-36, Amberlite (e.g., Amberlite IRC120), Dowex D 2030, Nafion NR50, and Nafion SAC13.

[0101] The term "acidic site functionalized oxide" refers to oxides such as zirconium oxide, aluminum oxide, or silicon dioxide, which are functionalized to produce materials such as sulfonated or sulfonated materials. Such solid acidic metal oxides may optionally be supported on a carrier material.

[0102] The term "acidic oxide" refers to metal oxides that exhibit Brønsted acidity, such as niobium oxide or aluminum oxide.

[0103] As used herein, the term "zeolite" refers to natural and synthetic microporous crystalline silicate materials (including aluminosilicates, borosilicates, and aluminoborosilicates) having a defined crystal structure determined by X-ray diffraction. Zeolites contain channel systems that can interconnect with other channel systems or cavities (e.g., side pockets or cages). The channel systems can be three-dimensional, two-dimensional, or one-dimensional. Zeolites contain SiO4 and XO4 tetrahedra, where X can be Al (aluminum) or B (boron). Zeolites can contain combinations of AlO4 and BO4 tetrahedra. In one embodiment, X is Al, and the zeolite does not contain BO4 tetrahedra. The SiO4 and XO4 tetrahedra are connected at their corners by common oxygen atoms. "The Atlas of Zeolite Framework Types" (C. Baerlocher, LB. McCusker, DH. Olson, 6th edition. Elsevier, Amsterdam, 2007), along with its web-based version (http: / / www.iza-structure.org / databases / ), provides a summary of the topological and structural details of zeolite frameworks, including the types of ring structures present in zeolites and the dimensions of channels defined by each ring type. Empirical formulations and good laboratory practices for zeolite synthesis are available in "Verified synthesis of zeolitic materials," 2nd edition, 2001. Various validated formulations for the synthesis of BO tetrahedra are available. For example, Cichocki and Parasiewicz-Kaczmarska (Zeolites 1990, 10, 577-582) describe the synthesis and characterization of boron-based zeolites with MFI topologies.

[0104] Suitable zeolites for use in the method according to the invention may comprise:

[0105] - At least two (preferably two or three) non-interconnected and parallel channel systems, wherein at least one of the channel systems contains 8-membered or more ring-shaped channels; and a framework Si / X2 ratio of at least 4 as measured by NMR; or

[0106] - At least two (preferably two or three) interconnected and non-parallel channel systems, wherein at least one of the channel systems comprises a 10-membered or more ring-shaped channel; and a framework Si / X2 ratio of at least 4 as measured by NMR; or

[0107] - Three interconnected and non-parallel channel systems, wherein at least two of the channel systems contain 10-membered or more ring channels and a framework Si / X2 ratio of at least 4 as measured by NMR.

[0108] Each X is either Al or B.

[0109] As used herein, the term "channel system" refers to a system of parallel or non-parallel, crystallographically equivalent channels, wherein the channels are 8-membered ring channels or more, such as 10-membered ring channels or 12-membered ring channels. Therefore, as used herein, the term "channel" refers to an 8-membered or more ring-membered channel that is part of a system of parallel or non-parallel, crystallographically equivalent channels.

[0110] Suitable zeolites used in this method contain 10-membered or more ring channels, such as 12-membered ring channels (12MR), or more ring channels. The ring dimensions for each known zeolite framework type are provided in "The Atlas of Zeolite FrameworkTypes" (C Baerlocher, LB McCusker, DH Olson, 6th edition. Elsevier, Amsterdam, 2007), which is incorporated herein by reference.

[0111] As used herein, the term "8-membered ring channel" or "8MR" refers to a channel containing an unobstructed 8-membered ring, where the 8-membered ring defines the minimum diameter of the channel. The 8-membered ring contains eight T atoms and eight alternating oxygen atoms (forming rings), where each T is Si, Al, or B. As used herein, the term "10-membered ring channel" or "10MR" refers to a channel containing an unobstructed 10-membered ring, where the 10-membered ring defines the minimum diameter of the channel. The 10-membered ring contains ten T atoms and ten alternating oxygen atoms (forming rings), where each T is Si, Al, or B. As used herein, the term "12-membered ring channel" or "12MR" refers to a channel containing an unobstructed 12-membered ring, where the 12-membered ring defines the minimum diameter of the channel. The 12-membered ring contains twelve T atoms and twelve alternating oxygen atoms (forming rings), where each T is Si, Al, or B. As used herein, the term "10- or more cyclic channels" refers to 10- or more cyclic channels, and therefore includes, for example, both 10- or 12-cycle channels.

[0112] The framework Si / X2 ratio can be determined by nuclear magnetic resonance (NMR), specifically by 29Si and 27Al NMR. In a preferred embodiment, framework B is absent, and the Si / X2 ratio is equal to the Si / A ratio. The Si / A ratio can be determined by NMR as described by Klinowski (Ann. Rev. Mater. Sci. 1988, 18, 189-218); or as described by G. Engelhardt and D. Michel (High-Resolution Solid-State NMR of Silicates and Zeolites. John Wiley & Sons, Chichester 1987. xiv, 485 pp). The determination of the Si / B2 ratio by NMR can be performed as discussed by D. Trong On et al. (Studies in Surface Science and Catalysis 1995, 97, 535-541; Journal of Catalysis, November 1995, Vol. 157, No. 1, pp. 235-243).

[0113] Zeolites are thermally stable catalysts and can therefore be regenerated by calcination, in contrast to traditional thermally unstable ion exchange resins such as Amberlyst-15.

[0114] The advantage of heterogeneous catalysts is that they provide high product separability, while also offering high recovery rates and easy adjustment to specific conditions (tunability).

[0115] Further disclosed is a method for preparing acetal-protected lignin fragments, comprising the following steps: reacting the diol groups of a lignocellulose-containing material with one or both of a compound of formula (Ia) and / or formula (Ib) in the presence of a homogeneous or heterogeneous catalyst.

[0116]

[0117] To form lignin fragments protected by acetal with one or more -ZX functional groups,

[0118] in

[0119] Z is a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, or an aromatic moiety having 6 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, and may be present or absent;

[0120] X is -CH(COOH)2, -COOR3, -C2H3, -C2H, -CHOR5OR6, -N3, -NHR7, -NR8R9, -F, -Cl, -Br or -I, or if Z is present, X is -OH, NH2 or -SH;

[0121] R3, R4 and R5 are each independently selected from and are straight-chain, branched or cyclic hydrocarbon moieties having 1 to 20 carbon atoms, optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms selected from the group consisting of fluorine, chlorine, bromine and iodine.

[0122] R6 is a C1-C4 alkyl group;

[0123] R7, R8, and R9 are each independently selected from and are C1-C4 alkyl groups;

[0124] R 30 and R 31 Each is independently selected from the group consisting of hydrogen and a straight-chain or branched hydrocarbon moiety having 1 to 4 carbon atoms, provided that R 30 and R 31 It cannot be hydrogen at the same time.

[0125] The preferred embodiments described regarding the method for preparing acetal-protected sugars are also applicable to the disclosed method for preparing acetal-protected lignin fragments. Specifically, the preferred embodiments discussed regarding the "method for preparing acetal-protected sugars" are equally applicable to the "method for preparing acetal-protected lignin fragments." The (preferred) definitions of the groups in formulas (Ia) and (Ib) given above in connection with acetal-protected sugars are similarly applicable to acetal-protected lignin fragments, unless otherwise specified.

[0126] The method disclosed herein for preparing acetal-protected lignin fragments has the following advantages: acetal-protected lignin fragments are obtained using acetal compounds of formula (Ia) and / or formula (Ib) as protecting agents. By using acetal as a reagent and in excess, the viscosity of the acetal-protected lignin fragments is reduced. This reduction in viscosity improves the scalability of the production method, which significantly reduces capital costs.

[0127]

[0128] Another advantage of the method of the present invention is that by using acetal as a reagent, the reactivity of common undesirable side reactions of aldehydes and ketones (such as aldol condensation) is significantly reduced.

[0129] Furthermore, the production method disclosed herein is not limited to a specific type of catalyst, as the reaction can be catalyzed by either homogeneous or heterogeneous catalysis. On the one hand, Lewis acids are efficient, cost-effective, and shorten reaction time. On the other hand, heterogeneous catalysts also perform well and simplify post-processing, as they can be filtered and recovered.

[0130] Preferred embodiments of this disclosure relate to a method for preparing lignin fragments protected by acetal and having one or more functional groups -ZX.

[0131] The following reaction scheme discloses the preparation of acetal-protected lignin fragments, where Y is H or OMe.

[0132]

[0133] Preferred embodiments of this disclosure relate to a method for preparing lignin fragments protected by acetal with one or more functional groups -Z-COOR3, wherein Z and R3 are as defined above.

[0134] The following reaction scheme discloses the preparation of acetal-protected lignin fragments having a functional group (here -COOR3), where Y is H or OMe and R3 is as defined above.

[0135]

[0136] A more preferred embodiment of this disclosure relates to a method for preparing lignin fragments protected by acetal having one or more functional groups -Z-COOR3, wherein Z is absent.

[0137] Acetal-protected lignin allows for the attachment of functional groups (here, -ZX) to the lignin backbone, expanding its potential uses in a variety of applications, including its use as a surfactant or in thermosetting resins.

[0138] The following reaction scheme illustrates the preparation of acetal-protected lignin fragments with two functional groups (here -ZX).

[0139] Attached Figure Description

[0140] Figure 1 shows the viscosity measurements of DGAX and DEGX synthesized at 90°C as a function of time.

[0141] Figure 1 shows the change in viscosity of the reaction mixture over time during the synthesis of xylose diglyoxylate (DGAX) and xylose diglyoxylate methyl ester (DEGX).

[0142] The DGAX synthesis was carried out according to the synthesis described in EP4045514A1, using 4 equivalents of glyoxylic acid and 0.2 equivalents of sulfuric acid.

[0143] DEGX was synthesized according to Example 5 described in the Experimental Section below, using 4 equivalents of EDEA and 0.5 g Amberlyst 15 per gram of xylose.

[0144] As can be seen from the graph, the viscosity of the reaction mixture is highly variable during the synthesis of DGAX using glyoxylic acid, reaching a very high value at the end. Conversely, during the synthesis of DEGX using ethyl diethoxylate (EDEA), the viscosity of the reaction mixture remains at a lower level throughout the reaction time. This clearly demonstrates that using an acetal form of glyoxylate (such as ethyl diethoxylate (EDEA)) reduces the viscosity of the reaction product compared to using glyoxylic acid.

[0145] Example

[0146] Experimental data

[0147] Example 1

[0148] D-xylose (3.0 g, 33 mmol, 1.0 equivalent), ethyl acetate diethoxylate (14.1 g, 4 equivalent), and sulfuric acid (32.3 mg, 0.2 equivalent) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 3 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 64%.

[0149] Example 2

[0150] D-xylose (3.0 g, 33 mmol, 1.0 equivalent), ethyl acetate diethoxylate (21.0 g, 6 equivalent), and phosphomolybdic acid (0.75 g, 6.2 mol% H2O) were added. + The solution was added to a 50 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 5 hours. The resulting solution was cooled to room temperature (~23-25 ​​°C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 89%.

[0151] Example 3

[0152] D-xylose (3.0 g, 33 mmol, 1.0 equivalent), ethyl acetate diethoxylate (14.1 g, 4 equivalent), and tungstic acid (2.25 g) were added to a 50 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 5 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, further experiments were conducted to extract the catalyst from the reaction by liquid-liquid extraction, followed by distillation to recover 74% of the theoretically unconsumed EDEA equivalent, with a purity >95% as indicated by quantitative NMR. The reaction yielded a 33% DEGX separation.

[0153] Example 4

[0154] D-xylose (3.0 g, 33 mmol, 1.0 equivalent), ethyl acetate diethoxylate (14.1 g, 4 equivalent), and sulfated silica (2.25 g) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 6 hours. The resulting solution was cooled to room temperature (~23–25 °C). The yield was monitored by GC-FID. After acetal exchange, the yield was 55%.

[0155] Example 5

[0156] D-xylose (1.9 g, 13 mmol, 1.0 equivalent), ethyl acetate diethoxylate (13.6 g, 80 mmol, 6 equivalent), and Amberlyst-15 (0.94 g) were added to a 50 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 7 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID and reached 80%. After acetal exchange, further experiments were conducted to extract the catalyst from the reaction by liquid-liquid extraction, and then 56% of the EDEA equivalent was recovered by distillation from the theoretically unconsumed EDEA equivalent. Quantitative NMR showed that the purity was >95%, and the reaction yielded a 50% DEGX separation yield.

[0157] Example 6

[0158] D-xylose (1.3 g, 8.5 mmol, 1.0 equivalent), recovered ethyl acetate-recovered EDEA (8.7 g, 50 mmol, 6 equivalent), and Amberlyst-15 (0.67 g) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 3 hours and 30 minutes. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 84%.

[0159] Example 7

[0160] D-xylose (1.9 g, 13 mmol, 1.0 equivalent), ethyl acetate diethoxylate (13.6 g, 80 mmol, 6 equivalent), and ferric(III) chloride (0.82 g, 5.2 mmol, 0.4 equivalent) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 2 hours and 30 minutes. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 81%.

[0161] Example 8

[0162] D-xylose (1.9 g, 13 mmol, 1.0 equivalent), ethyl acetate diethoxylate (7.0 g, 40 mmol, 3 equivalent), γ-valerolactone-GVL (3.9 g, 40 mmol, 3 equivalent), and ferric(III) chloride (0.84 g, 5.2 mmol, 0.4 equivalent) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 3 hours and 30 minutes. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 78%.

[0163] Example 9

[0164] D-xylose (1.9 g, 13 mmol, 1.0 equivalent), methyl dimethoxyacetate-MDMA (10.4 g, 78 mmol, 6 equivalent), and ferric(III) chloride (1.05 g, 6.5 mmol, 0.5 equivalent) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 5 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 41%.

[0165] Example 10

[0166] D-xylose (1.9 g, 13 mmol, 1.0 equivalent), methyl dimethoxyacetate-MDMA (5.1 g, 38 mmol, 3 equivalent), γ-valerolactone-GVL (4 g, 40 mmol, 3 equivalent), and ferric(III) chloride (0.84 g, 5.2 mmol, 0.4 equivalent) were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (50 mbar) with a stir bar (500 rpm) for 2 hours and 30 minutes. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 40%.

[0167] Example 11

[0168] A 50 wt% aqueous solution of glyoxylic acid was placed in a round-bottom flask and dried under reduced pressure. Ethanol was added, and the mixture was heated at 85°C for 4 hours. The resulting solution was fractionally distilled to obtain a mixture of ethyl glyoxylate, ethyl diethoxylate, and ethyl ethoxyhydroxylate.

[0169] D-xylose (16.87 g, 112 mmol, 1.0 equivalent), ethyl glyoxylate, ethyl diethoxylate, and a mixture of ethyl ethoxyhydroxylate (59.22 g, 4.7 g, 0.2 equivalent) and silica sulfuric acid were added to a 100 mL round-bottom flask. The mixture was heated to 90 °C under reduced pressure (100 mbar) for 8 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the catalyst was filtered, washed with ethanol, and dried at 80 °C to recover 88 wt% of silica sulfuric acid as a white powder. The glyoxylate mixture (27.53 g) was recovered by distillation, and the reaction yielded a 23% DEGX separation yield.

[0170] Example 12

[0171] D-xylose (1.0 g, 1.0 equivalent), chloroacetaldehyde dimethyl acetal (CADMA) (4.0 equivalent), γ-valerolactone (10 mL), and heteropoly acid (phosphotungstic acid, 2.0 mol%) were added to a 50 mL round-bottom flask. The mixture was heated to 50 °C under reduced pressure (500 mbar) with a stir bar (500 rpm) for 5 hours. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 19%.

[0172] Example 13

[0173] D-xylose (1.0 g, 1.0 equivalent), bromoacetaldehyde dimethyl acetal (BADMA) (4.0 equivalent), γ-valerolactone (10 mL), and heteropoly acid (silicotungstic acid, 0.1 g) were added to a 50 mL round-bottom flask. The mixture was heated to 75 °C under reduced pressure (300 mbar) with a stir bar (500 rpm) for 1 hour. The resulting solution was cooled to room temperature (~23–25 °C), and the yield was monitored by GC-FID. After acetal exchange, the yield was 24%.

[0174] Example 14

[0175] D-xylose (300 mg, 2 mmol, 1.0 equivalent), FeBr3 (11.8 mg, 40 μmol, 4 mol%), 1,4-dioxane (5 mL), and acrolein dimethyl acetal (817 mg, 8 mmol, 4 equivalent) were added to a 10 mL round-bottom flask and sealed with a diaphragm. The reaction was stirred at 70 °C for 6 hours. After cooling to room temperature, the mixture was filtered through a silica gel septum. Further purification by rapid column chromatography (SiO2; ethyl acetate:hexane = 1:1) yielded 159 mg of divinylxylose (DVX) as a colorless oil (35% separation yield).

[0176] Example 15 (as part of the disclosure)

[0177] Weigh 4.5 g of extracted and dried biomass (birch) and transfer it to a 100 mL round-bottom flask containing an oval-shaped PTFE-coated stir bar. Add 4.8 mL of chloroacetaldehyde dimethyl acetal (CADMA), 25 mL of 1,4-dioxane, and 0.85 mL of 37% (wt / wt) hydrochloric acid sequentially to the flask. Then connect a condenser to the flask and a cooling water source, and install a gas bubbler on top of the reflux condenser to create a gas lock. Heat the mixture to 80°C for 3 hours with stirring, then allow it to cool to room temperature. Filter the cellulose and wash with dioxane and methanol. Remove 1,4-dioxane and CADMA by distillation, and dissolve the lignin in 1,4-dioxane and precipitate it in hexane. Subsequently, the precipitated lignin (100 mg) was hydrogenolyzed for 3 hours at 250 °C in dioxane (20 mL) with Ru / C (5 wt%, 100 mg) under H2 pressure (50 bar). The monomer yield after hydrogenolysis was 4.41 wt% biomass (by GC-FID), and the lignin extraction rate was 13.2 wt% biomass.

[0178] Example 16 (as part of the disclosure)

[0179] Weigh 3.5 g of extracted and dried biomass (birch) and transfer it to a 100 mL round-bottom flask containing an oval-shaped PTFE-coated stir bar. Add 25 mL of ethyl acetate diethoxylate (EDEA) and 0.54 mL of 98% (wt / wt) sulfuric acid sequentially to the flask. Connect a condenser to the flask and a cooling water source, and install a gas bubbler on top of the reflux condenser to create a gas lock. Heat the mixture to 85°C for 3 hours with stirring, then allow it to cool to room temperature. Filter the cellulose and wash with dioxane and methanol. Remove 1,4-dioxane and EDEA by distillation, and dissolve the lignin in ethyl acetate and precipitate it in diethyl ether. Subsequently, hydrogenolyze the precipitated lignin (100 mg) in dioxane (20 mL) with Ru / C (5 wt%, 100 mg) at 250°C under H2 pressure (50 bar) for 3 hours. The monomer yield after hydrogenolysis was 0.3 wt% of biomass (by GC-FID), and the lignin extraction rate was 5.9 wt% of biomass.

[0180] Example 17 (as part of the disclosure)

[0181] Weigh 3.5 g of extracted and dried biomass (birch) and transfer it to a 100 mL round-bottom flask containing an oval-shaped PTFE-coated stir bar. Add 25 mL of ethyl acetate diethoxylate (EDEA) and 0.79 g of 37% (wt / wt) hydrochloric acid sequentially to the flask. Then connect a condenser to the flask and a cooling water source, and install a gas bubbler on top of the reflux condenser to create a gas lock. Heat the mixture to 80°C for 3 hours with stirring, then allow it to cool to room temperature. Filter the cellulose and wash with dioxane and methanol. Remove 1,4-dioxane and CADMA by distillation, and dissolve the lignin in 1,4-dioxane and precipitate it in hexane. Subsequently, hydrogenolyze the precipitated lignin (100 mg) in dioxane (20 mL) with Ru / C (5 wt%, 100 mg) at 250°C under H2 pressure (50 bar) for 3 hours. The monomer yield after hydrogenolysis was 1.2 wt% of biomass (by GC-FID), and the lignin extraction rate was 6.1 wt% of biomass.

[0182] entry:

[0183] Item 1: A method for preparing acetal-protected sugars, comprising the steps of: reacting a diol group of a lignocellulose-containing material with one or both of a compound of formula (Ia) and / or formula (Ib) in the presence of a homogeneous or heterogeneous catalyst to form an acetal-protected lignin fragment having one or more functional groups -ZX.

[0184]

[0185] in

[0186] Z is a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, or Z is -BD, wherein

[0187] B is a straight-chain hydrocarbon moiety with 1 to 3 carbon atoms, and may or may not be present.

[0188] D is an aromatic moiety having 6 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups, 1 to 2 -OH groups, 1 to 2 -OCH3 groups, or 1 to 4 halogen atoms and combinations thereof, wherein

[0189] Z may or may not exist, and

[0190] X is -COOH, -CH(COOH)2, -COOR3, CHO, -C2H3, -C2H, -CHOR4OR5, -N3, -NHR6, -NR7R8, -F, -Cl, -Br, -I, or if Z is present, X is -OH, NH2, or -SH;

[0191] R3, R4 and R5 are each independently selected from and are straight-chain, branched or cyclic hydrocarbon moieties having 1 to 20 carbon atoms, optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms selected from the group consisting of fluorine, chlorine, bromine and iodine.

[0192] R6 is a C1-C4 alkyl group;

[0193] R7, R8, and R9 are each independently selected from and are C1-C4 alkyl groups;

[0194] R 30 and R 31 Each is independently selected from the group consisting of hydrogen and a straight-chain or branched hydrocarbon moiety having 1 to 4 carbon atoms, provided that R 30 and R 31 It cannot be hydrogen at the same time.

[0195] Item 2: The method according to Item 1, wherein compound (Ia) and / or compound (Ib) are selected from the group consisting of:

[0196]

[0197] .

[0198] Item 3: The method according to Item 1, wherein the reaction is carried out under solvent-free conditions.

[0199] Item 4: The method according to Item 1, wherein the reaction is carried out in a solvent, preferably in a solvent selected from the group consisting of: dimethyl isosorbide; cyclic ethers, particularly 1,4-dioxane or 2-methyltetrahydrofuran; sulfolane, sulfolane; aliphatic acids, particularly acetic acid; alkylpyrrolidones, cyclic carbonates; cyclic esters, particularly γ-valerolactone or γ-butyrolactone; acetonitrile and noncyclic ethers, particularly diethyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, triethylene glycol monoether / triethylene glycol diether.

[0200] Item 5: The method according to any one of the preceding items, wherein unreacted compounds of formula (Ia) and / or formula (Ib) are recovered by distillation.

[0201] Item 6: The method according to any one of the preceding items, wherein Z is absent in compounds (Ia) and (Ib).

[0202] Item 7: The method according to any one of the preceding items, wherein R 30 and R 31 They are the same.

[0203] Item 8: The method according to any one of the preceding items, wherein Z is -CH2 or absent; X is Cl, Br or -COOR3; and R3 is -CH3 or -CH2CH3.

[0204] Item 9: The method according to any one of the preceding items, wherein R 30 R 31 It is the same as R3.

[0205] Item 10: The method according to any one of the preceding items, the method being used to prepare lignin fragments protected by acetal having one or more functional groups -Z-COOR3.

[0206] Item 11: The method according to any one of the preceding items, wherein the catalyst is a homogeneous catalyst.

[0207] Item 12: The method according to Item 11, wherein the homogeneous catalyst is an organic acid or an inorganic acid, preferably selected from the group consisting of H2SO4, H3PO4, HBr, HCl, phosphotungstic acid, phosphomolybdic acid, tungstic silicic acid, methanesulfonic acid and p-toluenesulfonic acid.

[0208] Item 13: The method according to any one of items 1-10, wherein the catalyst is a heterogeneous catalyst.

[0209] Item 14: The method according to any one of the preceding items, wherein the heterogeneous acid catalyst is a Brønsted acid catalyst, preferably selected from the group consisting of:

[0210] a. Acidic zeolite,

[0211] b. Acid-doped zeolite,

[0212] c. Acid-site functionalized resins,

[0213] d. Acidic site functionalized oxides,

[0214] e. Acidic oxides, and

[0215] f. The immobilized form of the homogeneous acid specified in item 11 is preferably silica sulfuric acid.

Claims

1. A method for preparing acetal-protected sugars, comprising the following steps: In the presence of a homogeneous or heterogeneous catalyst, the diol group of a sugar selected from the group consisting of pentoses and hexoses is reacted with one or both compounds of formula (Ia) and / or formula (Ib). To form sugars protected by acetals selected from the group consisting of compounds of formulas (II), (III), and (IV). Where R1 and / or R2 are each independently -ZX, and in Z is a straight-chain, branched, or cyclic hydrocarbon moiety having 1 to 10 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups or 1 to 4 halogen atoms, or Z is -BD, wherein B is a straight-chain hydrocarbon moiety with 1 to 3 carbon atoms, and may or may not be present. D is an aromatic moiety having 6 carbon atoms, optionally substituted with 1 to 4 C1-C4 alkyl groups, 1 to 2 -OH groups, 1 to 2 -OCH3 groups, or 1 to 4 halogen atoms and combinations thereof, and wherein Z may or may not exist, and X is -COOH, -CH(COOH)2, -COOR3, CHO, -C2H3, -C2H, -CHOR4OR5, -N3, -NHR6, -NR7R8, -F, -Cl, -Br, -I, or if Z is present, X is -OH, NH2, or -SH; R3, R4 and R5 are each independently selected from the group consisting of straight-chain, branched or cyclic hydrocarbon moieties having 1 to 20 carbon atoms, optionally substituted by 1 to 4 C1 to C4 alkyl groups and / or 1 to 4 halogen atoms selected from the group consisting of fluorine, chlorine, bromine and iodine. R6 is a C1-C4 alkyl group; R7, R8, and R9 are each independently a C1-C4 alkyl group; R 30 and R 31 Independently selected from the group consisting of hydrogen and a straight-chain or branched hydrocarbon moiety having 1 to 4 carbon atoms, provided that R 30 and R 31 It cannot be hydrogen at the same time; R 10 Independently selected from -H, -OH, -CH2OH, -OR 13 or -CH2OR 15 The group formed; R 11 and R 12 Independently selected from -OH or -OR 13 The group formed; R 13 R 14 and R 15 Independently selected from hydrocarbon moieties having 1 to 10 carbon atoms; and n and p are each independently 0 or 1.

2. The method according to claim 1, wherein compound (Ia) and / or compound (Ib) are selected from the group consisting of: 。 3. The method according to claim 1, wherein, The reaction was carried out under solvent-free conditions.

4. The method according to claim 1, wherein, The reaction is carried out in a solvent, preferably in a solvent selected from the group consisting of: dimethyl isosorbide; cyclic ethers, especially 1,4-dioxane or 2-methyltetrahydrofuran; sulfolane, sulfolane; aliphatic acids, especially acetic acid; alkylpyrrolidones, cyclic carbonates; cyclic esters, especially γ-valerolactone or γ-butyrolactone; acetonitrile and noncyclic ethers, especially diethyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, triethylene glycol monoether / triethylene glycol diether.

5. The method according to any one of the preceding claims, wherein unreacted compounds of formula (Ia) and / or formula (Ib) are recovered by distillation.

6. The method according to any one of the preceding claims, wherein Z is absent in compounds (Ia) and (Ib).

7. The method according to any one of the preceding claims, wherein R 30 and R 31 They are the same.

8. The method according to any one of the preceding claims, wherein Z is -CH2 or absent; X is Cl, Br or -COOR3; and R3 is -CH3 or -CH2CH3.

9. The method according to any one of the preceding claims, wherein R 30 R 31 It is the same as R3.

10. The method according to any one of claims 1-9, wherein the method is used to prepare compound (II).

11. The method according to any one of claims 1-9, wherein the method is used to prepare compound (III) or compound (IV).

12. The method according to any one of the preceding claims, wherein, The catalyst is a homogeneous catalyst.

13. The method according to claim 12, wherein, The homogeneous catalyst is an organic acid or an inorganic acid, preferably selected from the group consisting of H2SO4, H3PO4, HBr, HCl, phosphotungstic acid, phosphomolybdic acid, tungstic acid, methanesulfonic acid and p-toluenesulfonic acid.

14. The method according to any one of claims 1-11, wherein, The catalyst is a heterogeneous catalyst.

15. The method according to any one of the preceding claims, wherein, The heterogeneous acid catalyst is a Brønsted acid catalyst, preferably selected from the group consisting of: g. Acidic zeolites, h. Acid-doped zeolites, i. Acid-site functionalized resins, j. Acidic site functionalized oxides, k. Acidic oxides, and 1. The immobilized form of the homogeneous acid as specified in claim 12, preferably silica sulfuric acid.

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