Synthesis of polycyclic disalicylate linkers

Abstract

A system and method for synthesizing polycyclic disalicylate linkers is provided. The system and method allow for the synthesis of disalicylate linkers while reducing or minimizing the amount of solvent in the reaction environment (possibly even having no separate solvent). The synthesis can be carried out starting with a compound such as 4,4'-biphenol as a starting reagent. 4,4'-biphenol (and / or other alcohol-substituted biphenyl compounds) can then be exposed to pressurized CO2 in the presence of a base in the reaction environment. The temperature and pressure in the reaction environment can be increased to achieve either supercritical conditions of CO2 (based on the phase diagram of neat CO2) and / or subcritical conditions substantially similar to the supercritical conditions. This allows the conversion of 4,4'-biphenol (or other alcohol-substituted biphenyl compounds) to polycyclic disalicylate linkers.

Description

[Technical field]

[0001] Methods for the synthesis of disalicylate compounds, including disalicylate compounds useful as linkers for forming metal-organic framework materials, are provided. [Background technology]

[0002] Metal-organic framework materials are compounds that contain metal ions coordinated by bidentate linkers (or other polydentate linkers) to form crystalline structures. Depending on the nature of the metal and the linker, metal-organic frameworks can have a variety of commercially interesting properties.

[0003] One group of metal-organic framework materials of interest for use in separation and / or catalytic applications are metal-organic framework materials that contain polycyclic disalicylate linkers. MOF-274 is an example of a metal-organic framework material that contains a polycyclic disalicylate linker. Metal-organic framework materials based on polycyclic disalicylate linkers may be used for selective adsorption of CO2 and / or other components from fluid streams.

[0004] One of the difficulties in applying materials such as MOF-274 to commercial applications is that polycyclic disalicylate linkers are relatively expensive to produce using existing methods. Some conventional methods for the synthesis of polycyclic disalicylate linkers represent methods that are difficult to scale up for the production of commercial quantities of the linkers. In addition, or alternatively, some synthetic methods may require high-cost starting materials as reagents. What is needed is an improved method for synthesizing disalicylate linkers that can be easily scaled up to synthesize larger quantities of the linkers while simultaneously reducing or minimizing the costs associated with the synthesis.

[0005] US 2021 / 0230092 describes a method to form 4,4'-dihydroxy-[1,1'-biphenyl-3,3'-dicarboxylic acid] based on the reaction of 4,4-biphenol in an amide solvent (such as dimethylformamide) in the presence of a base. The reaction is described as beneficial in that it provides a synthetic route that can be carried out at lower pressures and temperatures than traditional synthetic methods. Summary of the Invention

[0006] In various embodiments, a method for producing a polycyclic disalicylate compound is provided. The method includes forming a reagent mixture. In some embodiments, the reagent mixture can consist essentially of a polycyclic aromatic alcohol and a base in a reactor volume. In other embodiments, the reagent mixture can include a polycyclic aromatic alcohol, a base, and a solvent in a reactor volume, the solvent including 50 vol% or more of dioxane. The method further includes adding CO2 to the reactor volume. The method further includes heating the reactor volume to a process temperature of 150° C. or more, the reactor volume having a total pressure of 1.0 MPa-a or more at the process temperature. Additionally, the method includes maintaining the reactor volume at the process temperature for 0.5 hours or more to form a product mixture including a polycyclic disalicylate product. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 shows the H-NMR characteristics of the reaction products by forming a polycyclic disalicylate product according to the methods described herein.

[0008] [Diagram 2] FIG. 2 shows the 13C-NMR characteristics of the reaction products by forming the polycyclic disalicylate products according to the methods described herein.

[0009] [Diagram 3] FIG. 3 shows another example of H-NMR characterization of the reaction products by forming a polycyclic disalicylate product according to the methods described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] All numerical values ​​set forth in the detailed description and claims herein are modified by the word "about" or "approximately" to account for expected experimental error and variations that would be expected by one of ordinary skill in the art.

[0011] In various embodiments, systems and methods are provided for synthesizing polycyclic disalicylate linkers. The systems and methods allow for the synthesis of disalicylate linkers while reducing or minimizing the amount of solvent in the reaction environment (e.g., potentially having no separate solvent). The synthesis can be performed starting with a compound such as 4,4'-biphenol as a starting reagent. 4,4'-biphenol (and / or other alcohol-substituted biphenyl compounds) can then be exposed to pressurized CO2 in the presence of a base in the reaction environment. In some embodiments, the base can correspond to a solid base such as KHCO3, K2CO3, NaOH, or other suitable selection. The temperature and pressure of the reaction environment can be increased to achieve either supercritical conditions of CO2 (based on the phase diagram of neat CO2) and / or subcritical conditions substantially similar to the supercritical conditions. This allows the conversion of 4,4'-biphenol (or other alcohol-substituted biphenyl compounds) to polycyclic disalicylate linkers.

[0012] Traditionally, the formation of polycyclic disalicylate linkers has been carried out in a solvent environment. The solubility of the reagents for forming polycyclic disalicylate linkers in water is relatively low, so traditional solvents correspond to solvents such as trichlorobenzene or dimethylformamide. Although such solvent-based synthetic methods are effective for producing polycyclic disalicylate linkers, there are several challenges when it comes to scaling up to produce metal-organic framework materials on a commercial scale. First, such solvent-based synthetic methods often have difficulties when trying to change the synthetic conditions from laboratory-scale beakers to commercial-scale production tanks. Second, solvents such as trichlorobenzene and dimethylformamide are dangerous, so it is desirable to avoid large reactors containing large amounts of such materials.

[0013] In contrast to such conventional methods, it has been discovered that polycyclic disalicylate compounds can be formed by exposing polycyclic aromatic alcohol compounds to CO2 in the presence of a base under supercritical or near supercritical temperature and pressure conditions. The temperatures and pressures required to achieve the supercritical state of CO2 (according to the phase diagram of neat CO2) are well understood from the standpoint of reactor design. By using such high temperatures and pressures, the need for a solvent can be substantially or entirely avoided. Although a solvent can be included in the reaction environment, the volume of the solvent included in the reaction environment can be kept relatively small, since no solvent is required. Furthermore, since no solvent is required, the "solvent" included in the reaction environment can optionally correspond to a solvent that provides limited solubility for the reagents used to prepare the polycyclic disalicylate linker.

[0014] It should be noted that the reaction conditions of the synthesis described herein are similar to those of the Kolbe-Schmitt reaction that can be used, for example, to produce salicylic acid. However, by using a polycyclic aromatic alcohol compound as the polycyclic reagent, various process advantages can be obtained. First, the reaction can be carried out at a reaction pressure that is sub-supercritical with respect to the phase diagram of pure CO2. This is beneficial for commercial scale-up, since it reduces or minimizes the structural requirements of the pressurized vessel to carry out the reaction.

[0015] Second, depending on the target compound, the synthetic conditions for forming polycyclic disalicylate compounds can offer unexpected advantages in terms of product purity compared to the traditional Kolbe-Schmitt reaction. In particular, depending on the desired disalicylate product, forming polycyclic disalicylates can avoid the stereochemical uncertainties that can be associated with the traditional Kolbe-Schmitt process. When using the traditional Kolbe-Schmitt reaction to form salicylic acid from sodium phenoxide, CO2 addition can occur at both the ortho and para positions on the aromatic ring. In contrast, depending on the desired disalicylate product, a higher degree of control over the reaction product can be achieved. For example, when using 4,4-biphenol as the polycyclic reagent, the para position is occupied by the biphenyl bond and therefore unavailable for reaction with CO2. Because this biphenyl bond is free to rotate, either ortho position will give the same product. This offers the unexpected advantage of being able to use a Kolbe-Schmitt style process while producing a reaction product that is substantially free of isomers.

[0016] In addition to the advantages over the Kolbe-Schmitt type process, the synthesis of polycyclic disalicylate compounds as described herein can share some of the advantages of the Kolbe-Schmitt type process.For example, the Kolbe-Schmitt type reaction has already been used industrially to produce salicylic acid (as a precursor to aspirin production).Therefore, in contrast to the laboratory-scale method for producing polycyclic disalicylates, the synthesis method described herein is believed to be easily scaled up for the production of commercial amounts of polycyclic disalicylate compounds.

[0017] Another advantage of using high-pressure, high-temperature CO2 as the reaction environment is that such an environment can simplify the recovery of the disalicylate product compound. Reagents such as 4,4'-biphenol have relatively low solubility in water and alcohol. In contrast, polycyclic disalicylate compounds are generally soluble in water and often in a wide variety of alcohols. Therefore, after carrying out the synthesis reaction to produce a polycyclic disalicylate, the product compound (disalicylate) can be separated from the unreacted polycyclic reagent (e.g., 4,4-biphenol) by adding water to the product. The unreacted polycyclic reagent can be separated from the resulting mixture by filtration. The water can then be acidified to precipitate the desired disalicylate product.

[0018] It should be noted that the compound resulting from this synthesis is described as a disalicylate. It is understood that compounds with more than one salicylic acid group can also be formed using the appropriate starting reagent with more than two alcohol groups attached to the aromatic ring. For the purposes of illustrating the synthetic method, in this discussion, the product compound will be described as a disalicylate.

[0019] definition For purposes of this discussion, polycyclic compounds containing two or more hydroxyls attached to aromatic rings are defined as polycyclic aromatic alcohols, regardless of other substituents that may be present in the compound. In some embodiments, the carbon atoms in at least two different aromatic rings in a polycyclic aromatic alcohol may correspond to the carbon atoms attached to the hydroxyl groups. For purposes of this definition, rings in a fused ring structure are counted as separate rings, so naphthalene (C 10 H8) is defined as a compound that contains two aromatic rings.

[0020] In various embodiments, the aromatic rings of the polycyclic aromatic alcohols can contain only carbon atoms, and no "heteroatoms" such as nitrogen or oxygen are present in the aromatic rings of the polycyclic aromatic alcohols. Without being bound to any particular theory, it is believed that the presence of such heteroatoms inhibits the reaction mechanism.

[0021] As used herein, the term "polycyclic" is defined to refer to compounds that contain two or more ring structures (i.e., cyclic structures). The rings can correspond to fused rings, such as naphthalene-type structures, rings that are non-covalently linked, such as biphenyl bonds, or rings that are separated by one or more atoms, such as rings separated by methyl bonds. This is in contrast to monocyclic compounds. Polycyclic compounds can contain multiple aromatic rings, multiple non-aromatic rings (such as saturated rings and / or rings that contain an insufficient number of double bonds to provide aromaticity), or combinations thereof.

[0022] For purposes of this discussion, a reactor is defined as any vessel, container, pipe, or other structure that can be used to provide a pressurized, high temperature reaction environment for carrying out the reactions described herein.

[0023] Synthesis and product recovery In various embodiments, polycyclic disalicylate compounds can be formed by exposing a reagent to CO under high temperature and pressure reaction conditions. The reaction environment for forming polycyclic disalicylate compounds can include a) a polycyclic alcohol reagent that includes two or more hydroxyl groups attached to carbons of an aromatic ring, b) a base, and c) CO.

[0024] In some embodiments, the reagents in the reaction environment may consist essentially of the polycyclic alcohol, the base, and CO2. In such embodiments in which the reagents in the reaction environment consist essentially of the polycyclic alcohol, the base, and CO2, other components such as an inert gas (e.g., N2) may be present in the reaction environment. Additionally, in such embodiments in which the reagents in the reaction environment consist essentially of the polycyclic alcohol, the base, and CO2, water may be present due to water of hydration associated with the reagents, although in some embodiments it may be preferable to dry the reagents prior to synthesis to remove the water of hydration. Water present as water of hydration may combine with water generated in situ during the reaction. Optionally, all of the reagents may be in solid form prior to the start of the synthesis procedure.

[0025] In other embodiments, a solvent can be present. When present, the solvent can preferably represent 50 vol% or more of dioxane. Conventional synthesis solvents for disalicylates, such as trichlorobenzene or dimethylformamide, can also be included, but it should be noted that including such solvents tends to reduce some of the advantages of the synthesis method. In particular, including such solvents tends to increase the restrictions and / or special procedures required to carry out the reaction.

[0026] The polycyclic alcohol reagent can correspond to a polycyclic compound that includes at least two hydroxyl (-OH) groups attached to carbons of aromatic rings in the compound. The reagent can be selected so that the relative positions of the alcohol groups in the reagent match the positions of the hydroxyl group moieties of the salicylic acid group in the desired or target compound. At least one "ortho" position on the aromatic ring to each hydroxyl group must also be available to allow for the addition of CO2 to form the carboxylate group. In some embodiments, some advantages may be provided by having both "ortho" positions available to reduce or minimize the negative impact on yield of having a substituent at a position that is "meta" to the position where the carboxylate group is added. It should be noted that the formation of disalicylate requires the presence of at least two alcohol groups in the polycyclic alcohol reagent compound.

[0027] An example of a polycyclic alcohol reagent is 4,4'-biphenol. By adding a carboxylate group ortho to each alcohol group, the compound 4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid can be formed. This compound can be called H4DOBPDC. Adding a carboxylic acid at the ortho position would produce the same compound because the biphenyl bond is free to rotate and there is no asymmetric center.

[0028] Another reagent can be a base. Examples of suitable bases include, but are not limited to, alkali carbonates, alkali bicarbonates, and alkali hydroxides. Examples of bases include, but are not limited to, KOH, KHCO3, K2CO3, NaOH, NaHCO3, Na2CO3, and mixtures thereof. It should be noted that the base plays a stoichiometric role in the reaction environment, resulting in the formation of water as a by-product of the reaction that adds the carboxylate group to the ring. Additionally, CO2 serves as both a reagent and a reaction medium.

[0029] To begin the synthesis of the polycyclic disalicylate compound, the polycyclic alcohol reagent, base, and CO2 can be added to a reactor. The reactor is then heated and pressurized. The reactor can be heated and pressurized in any convenient order. For example, the reactor can be first pressurized to a first pressure value by adding gas phase CO2 at a temperature near 25°C. After the desired amount of CO2 has been added, the reactor can be heated. This will cause the pressure to increase further since the CO2 is in the gas phase or exists as a supercritical fluid. Pressurization and heating can be done in any convenient manner to achieve the target conditions for carrying out the reaction to form the polycyclic disalicylate compound.

[0030] In various embodiments, the reaction can be carried out by maintaining the reaction environment at a temperature of 150° C. or higher, or 200° C. or higher, or 250° C. or higher, for example, up to 500° C., or even higher in some cases. The temperature can be maintained within such target range for the reaction time. With respect to pressure, in various embodiments, the total pressure in the reaction environment can substantially correspond to the pressure of CO2 in the reaction environment. In various embodiments, the total pressure in the reaction environment can be maintained at 1.0 MPa-a or higher, or 3.5 MPa-a or higher, or 6.0 MPa-a or higher, or 7.38 MPa-a or higher, for example, up to 20 Mpa-a, or even higher in some cases. In some embodiments, the reaction environment can be maintained at a total pressure below the supercritical point of pure CO2 for the reaction time. In such an embodiment, the total pressure can be between 1.0 MPa-a and 7.35 MPa-a (i.e., below the supercritical pressure of 7.38 MPa-a), or between 3.5 MPa-a and 7.35 MPa-a, or between 5.0 MPa-a and 7.35 MPa-a, or between 6.0 MPa-a and 7.35 MPa-a, or between 1.0 MPa-a and 7.0 MPa-a, or between 1.0 MPa-a and 6.5 MPa-a, or between 3.5 MPa-a and 7.0 MPa-a during the reaction time. It is noted that the total pressure in the reaction environment may be higher than the pressure of CO2 due to the presence of other fluids. For example, water is evolved during the reaction to form the polycyclic disalicylate product. Although the molar amount of water is generally small relative to the molar amount of CO2 in the reaction environment, such water may nevertheless contribute to the total pressure being slightly higher than the pressure of CO2. If another solvent (such as dioxane) is added to the reagent mixture, the difference between the total pressure and the CO2 partial pressure will be greater.

[0031] The reaction environment can be maintained at a temperature and / or pressure within a target range for a reaction time of 0.5 hours to 48 hours, or 0.5 hours to 24 hours, or 0.5 hours to 12 hours, or 0.5 hours to 6.0 hours, or 4.0 hours to 8.0 hours. It is possible to use longer times, but it should be noted that such longer reaction times tend to reduce the achievable throughput of the reactor.

[0032] The amount of polycyclic aromatic alcohol reagent and base in the reaction environment can be selected such that the molar ratio of alcohol reagent to base in the reaction environment is between 0.3 and 3.0 (i.e., between 0.3 to 1 to 3.0 to 1.0), or between 0.15 and 3.0, or between 0.15 and 2.0, or between 0.5 and 2.0, or between 0.8 and 1.2. The amount of CO2 can be any convenient amount such that there is a substantial molar excess of CO2 in the reaction environment relative to the amount of polycyclic aromatic alcohol reagent, for example, to have a molar amount of CO2 that is at least 5.0 times the molar amount of polycyclic aromatic alcohol reagent. It should be noted that when CO2 is used to at least partially pressurize the reaction environment, there is typically a substantial molar excess of CO2.

[0033] Optionally, a solvent can also be included in the reaction environment. Dioxane is an example of such a solvent. In some embodiments, the amount of solvent can be reduced or minimized so that the weight of the solvent is comparable to or less than the total weight of the polycyclic aromatic alcohol and the base in the reaction environment. In such embodiments, the weight of the solvent can be less than 3.0 times, or less than 2.0 times, or less than 1.0 times, or less than 0.5 times the total weight of the polycyclic aromatic alcohol and the base, for example, the reaction environment can be substantially free of solvent. It should be noted that even if the polycyclic aromatic alcohol and the base are introduced into the reaction environment as dry solid reagents, a small amount of water will be generated in situ in the reaction environment, since the reaction process for forming the polycyclic disalicylate compound stoichiometrically produces one water per salicylic acid group formed.

[0034] It should be noted that the use of water alone as a solvent is not effective for the formation of disalicylate linkers under the synthetic conditions described herein. However, it was unexpectedly discovered that dioxane can be used as a solvent. It was unexpected that dioxane can be used as a solvent when water cannot be used as a solvent due to the dipole moment of the solvent. In particular, it is known that dimethylformamide (dipole moment 3.86 debye) can be used as a solvent. Water (dipole moment 1.85 debye) does not result in significant formation of disalicylate when used as a solvent. However, dioxane (dipole moment 0.45 debye) does result in formation of disalicylate.

[0035] After maintaining the reaction environment at the target pressure and temperature range for the reaction time, the reaction can be stopped. The polycyclic disalicylate product can then be recovered by any convenient method. One option can be to add water (if necessary) to form a solution containing the polycyclic disalicylate product. Since the solubility of the polycyclic aromatic alcohol reagent in water is typically relatively low, the resulting water mixture can be, for example, filtered to remove the solid polycyclic aromatic alcohol reagent. It is noted that any polycyclic aromatic alcohol reagent recovered from the product can potentially be recycled for use again as a reagent. After filtration, the water mixture can be acidified to precipitate the polycyclic disalicylate product. The solid product can be recovered by any convenient method for separating solids from liquids.

[0036] Structure of polycyclic disalicylate compounds In general, the synthetic methods described herein can be used to prepare disalicylate compounds, which correspond to compounds that contain two monohydroxybenzoic acid groups.

[0037] In one embodiment, useful disalicylate linkers include: [ka]

[0038] Here, R1 is connected to R1' and R2 is connected to R2'.

[0039] Examples of such linkers include: [ka] where R is any molecular fragment.

[0040] An example of a disalicylate compound may be one that has two phenyl rings linked at carbon 1,1' (i.e., a biphenyl-type bond), a carboxylic acid at carbon 3,3', and an alcohol at carbon 4,4'. This compound may be called "H4DOBPDC."

[0041] Other examples of disalicylates include 4,4'-dioxidobiphenyl-3,3'-dicarboxylate (DOBPDC); 4,4''-dioxidobiphenyl-[1,1':4',1''-terphenyl]-3,3''-dicarboxylate (DOTPDC); and dioxidobiphenyl-4,4'-dicarboxylate (paracarboxylate-DOBPDC, also called PC-DOBPDC), as well as the following compounds: [ka]

[0042] In some embodiments, the disalicylate has the formula: [ka] has.

[0043] Here, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20are each independently selected from H, halogen, hydroxyl, methyl, and halogen-substituted methyl.

[0044] In some embodiments, the disalicylate has the formula: [ka] has.

[0045] Here, R 11 , R 12 , R 13 , R 14 , R 15 , and R 16 are each independently selected from H, halogen, hydroxyl, methyl, and halogen-substituted methyl.

[0046] In some embodiments, the organic linker has the formula: [ka] has.

[0047] Here, R 11 , R 12 , R 13 , R 14 , R 15 , and R 16 are each independently selected from H, halogen, hydroxyl, methyl, or halogen-substituted methyl; R 17 is selected from substituted or unsubstituted aryl, vinyl, alkynyl, and substituted or unsubstituted heteroaryl.

[0048] In some embodiments, the organic linker has the formula: [ka] has.

[0049] Here, R 11 , R 12 , R 13 , R 14 , R 15 , and R 16are each independently selected from H, halogen, hydroxyl, methyl, or halogen-substituted methyl.

[0050] Here, R 11 , R 12 , R 13 , R 14 , R 15 , and R 16 are each independently selected from H, halogen, hydroxyl, methyl, or halogen-substituted methyl; R 17 is selected from substituted or unsubstituted aryl, vinyl, alkynyl, and substituted or unsubstituted heteroaryl.

[0051] In certain embodiments, the organic linker comprises a multiple bridged aryl species, such as a molecule having two (or more) phenyl rings, or a molecule having two phenyl rings joined by a vinyl or alkynyl group.

[0052] Note that the above examples primarily correspond to structures in which two or more aromatic rings are linked via biphenyl bonds. In other embodiments, the polycyclic disalicylate linker can include an aromatic core of two or more fused aromatic rings.

[0053] Example 1 Synthesis of H4DOBPDC from 4,4'-biphenol (no solvent added) To prepare H4DOBPDC (4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), 10 g of 4,4'-biphenol was ground and dried in an oven at 120°C for approximately 3 hours. Separately, 16.13 g of solid base (KHCO3) was ground and dried in an oven at 120°C. The two solids were thoroughly mixed in a glass vessel, placed in an autoclave, sealed, and purged with N2. The vessel was then pressurized to approximately 3.7 MPa-a with CO2. The vessel was then heated to 280°C, increasing the pressure in the vessel to approximately 7.6 MPa-a. As a result, the CO2 in the vessel corresponded to supercritical CO2 (based on the phase diagram of pure CO2). The vessel was maintained at this temperature and pressure combination for approximately 24 hours. The reactor was then cooled and depressurized.

[0054] The reaction product in the vessel represented a mixture of solids. Water was added to the solids to form a solid-water mixture. The solid-water mixture was sonicated and vigorously stirred for at least 1 hour. The resulting slurry was filtered. The solids removed by filtration represented substantially unreacted 4,4'-biphenol. The filtrate was acidified with hydrochloric acid to a pH of less than 2, resulting in the precipitation of a white solid. The white solid was recovered by filtration. This white solid represented substantially pure H4DOBPDC. It should be noted that recrystallization can be performed to increase the purity of the product.

[0055] The H4DOBPDC sample formed according to the above method was analyzed by H-NMR and 13 The compounds were characterized using C-NMR. Figure 1 shows an example of a H-NMR spectrum obtained for a relatively pure H4DOBPDC sample produced by the method described herein, and Figure 2 shows 13 An example of a C-NMR spectrum is shown in Figure 1. The spectra shown in Figure 1 and Figure 2 show that H4DOBPDC was obtained.

[0056] Example 2 Synthesis of H4DOBPDC from 4,4'-biphenol (dioxane as solvent) To prepare H4DOBPDC (4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), 3.0 g of 4,4'-biphenol and 6.68 g of freshly ground K2CO3 were mixed in 40 mL of 1,4-dioxane with stirring. The resulting solution was placed in an autoclave, sealed, and purged with N2. The vessel was then pressurized with CO2 to approximately 3.7 MPa-a. The vessel was then heated to 280 °C overnight. After the reactor was returned to ambient temperature and pressure, the contents were dissolved in water and acidified with 10% hydrochloric acid in water. As a result, a solid precipitated out, which was recovered from the solution by filtration. The solid was dissolved in acetone, dried over MgSO4, and filtered. The filtrate was concentrated to give the diacid as a pale yellow solid.

[0057] A sample of the pale yellow solid was dissolved in dimethyl sulfoxide (DMSO) and characterized by H-NMR. Figure 3 shows the spectrum obtained, indicating that H4DOBPDC was obtained.

[0058] It should be noted that other convenient acids can be used to acidify the water to promote precipitation, for example sulfuric acid, and also, or alternatively, less concentrated acids can be used as the reagent to acidify the solution. Additional Embodiments

[0059] Embodiment 1. A method for preparing a polycyclic disalicylate compound, comprising: i) consisting essentially of a polycyclic aromatic alcohol and a base; or ii) forming a reagent mixture comprising a polycyclic aromatic alcohol, a base, and a solvent in a reactor volume, the solvent comprising at least 50 vol.% dioxane; adding CO2 to the reactor volume; heating the reactor volume to a treatment temperature of 150°C or greater; the reactor volume at the treatment temperature containing a pressure of 1.0 MPa-a or greater; and maintaining the reactor volume at the treatment temperature for at least 0.5 hours to form a product mixture comprising a polycyclic disalicylate product.

[0060] Embodiment 2. The method of embodiment 1, further comprising separating at least a portion of the polycyclic disalicylate product from the product mixture.

[0061] Embodiment 3. The method according to any of the above embodiments, wherein the total pressure at the treatment temperature is from 1.0 MPa-a to 7.35 MPa-a.

[0062] Embodiment 4. The method according to any of the above embodiments, wherein the total pressure at the treatment temperature is from 1.0 MPa-a to 6.5 MPa-a.

[0063] Embodiment 5. The method of embodiment 1 or 2, wherein the total pressure at the processing temperature is from 7.40 MPa-a to 20 MPa-a.

[0064] Embodiment 6. The method according to any of the above embodiments, wherein the treatment temperature is 150°C to 500°C.

[0065] Embodiment 7. The method of any of the above embodiments, wherein forming the reagent mixture includes forming a reagent mixture having a molar ratio of polycyclic aromatic alcohol to base from 0.5 to 2.0.

[0066] Embodiment 8. The method of any of the above embodiments, wherein the polycyclic aromatic alcohol comprises 4,4'-biphenol.

[0067] Embodiment 9. The method of any of the above embodiments, wherein the base comprises an alkali carbonate, an alkali bicarbonate, an alkali hydroxide, or a combination thereof.

[0068] Embodiment 10. The method of any of the above embodiments, wherein the polycyclic aromatic alcohol contains at least one hydroxyl group bonded to a carbon in an aromatic ring, and each carbon atom in an ortho position in the aromatic ring is bonded to a hydrogen.

[0069] Embodiment 11. The method of any of the above embodiments, wherein forming the reagent mixture includes forming a reagent mixture having a molar ratio of solvent to polycyclic aromatic alcohol of 3.0 or less.

[0070] Alternative Embodiment A. A method for producing a polycyclic disalicylate compound, comprising: forming a reagent mixture in a reactor volume consisting essentially of a polycyclic aromatic alcohol and a base; adding CO2 to the reactor volume; heating the reactor volume to a treatment temperature of 150°C or greater; the reactor volume containing a total pressure of 1.0 MPa-a or greater at the treatment temperature; and maintaining the reactor volume at the treatment temperature for at least 0.5 hours to form a product mixture comprising a polycyclic disalicylate product.

[0071] Alternative embodiment B. A method for producing a polycyclic disalicylate compound, comprising: forming a reagent mixture in a reactor volume comprising a polycyclic aromatic alcohol, a base, and a solvent, the solvent comprising at least 50 vol.% dioxane; adding CO2 to the reactor volume; heating the reactor volume to a treatment temperature of 150°C or greater; the reactor volume containing a total pressure of 1.0 MPa-a or greater at the treatment temperature; and maintaining the reactor volume at the treatment temperature for at least 0.5 hours to form a product mixture comprising a polycyclic disalicylate product.

[0072] Additional embodiment C. The method of any of embodiments 1 through 6 or 8 through 11, wherein forming the reagent mixture comprises forming a reagent mixture having a molar ratio of polycyclic aromatic to base from 0.15 to 2.0.

[0073] Certain features have been described with upper and lower numerical limits. It is understood that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Specific lower limits, upper limits and ranges are set forth in one or more claims below. All numerical values ​​account for experimental error and variations that would be expected by one of ordinary skill in the art.

[0074] The foregoing description of the disclosure illustrates and describes the method. Moreover, while the disclosure illustrates and describes exemplary methods, it will be understood that various other combinations, modifications, and environments may be employed, and that the method is capable of change or modification within the scope of the concepts expressed herein, commensurate with the above teachings and / or skill or knowledge of the relevant art.

Claims

1. 1. A method for producing a polycyclic disalicylate compound, comprising: i) consisting essentially of a polycyclic aromatic alcohol and a base; or ii) forming a reagent mixture comprising a polycyclic aromatic alcohol, a base, and a solvent in a reactor volume, the solvent comprising 50 vol. % or more of dioxane; CO ２ to a reactor volume; heating the reactor volume to a treatment temperature of 150° C. or greater; the reactor volume at said treatment temperature containing a total pressure of 1.0 MPa-a or greater; and maintaining the reactor volume at said treatment temperature for at least 0.5 hours to form a product mixture comprising a polycyclic disalicylate product.

2. 10. The process of claim 1 further comprising separating at least a portion of the polycyclic disalicylate product from the product mixture.

3. The method according to claim 1 or 2, wherein the total pressure at the treatment temperature is from 1.0 MPa-a to 7.35 MPa-a.

4. The method of claim 3, wherein the total pressure at the treatment temperature is from 1.0 MPa-a to 6.5 MPa-a.

5. The method according to claim 1 or 2, wherein the total pressure at the treatment temperature is from 7.40 MPa-a to 20 MPa-a.

6. The method according to any one of claims 1 to 5, wherein the treatment temperature is from 150°C to 500°C.

7. The method of any one of claims 1 to 6, wherein forming a reagent mixture comprises forming a reagent mixture having a molar ratio of polycyclic aromatic alcohol to base from 0.5 to 2.

0.

8. The method of any one of claims 1 to 6, wherein forming a reagent mixture comprises forming a reagent mixture having a molar ratio of polycyclic aromatic alcohol to base of from 0.15 to 2.

0.

9. The process according to any one of claims 1 to 8, wherein the polycyclic aromatic alcohol comprises 4,4'-biphenol.

10. The process of any one of claims 1 to 9, wherein the base comprises an alkali carbonate, an alkali bicarbonate, an alkali hydroxide, or a combination thereof.

11. The process according to any one of claims 1 to 10, wherein the polycyclic aromatic alcohol comprises at least one hydroxyl group attached to a carbon of an aromatic ring, and each carbon atom in the ortho position of the aromatic ring is bonded to a hydrogen.

12. The method of any one of claims 1 to 11, wherein forming a reagent mixture comprises forming a reagent mixture having a molar ratio of solvent to polycyclic aromatic alcohol of 3.0 or less.

13. The process according to any one of claims 1 to 12, wherein the reagent mixture consists essentially of the polycyclic aromatic alcohol and the base.

14. The method according to any one of claims 1 to 12, wherein the reagent mixture comprises a polycyclic aromatic alcohol, a base, and a solvent.

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