Synthesis of renewable terephthalates and aromatic diisocyanates from monosaccharides

Abstract

A process for the production of a terephthalate includes subjecting a compound of Formula (I) to an electrochemical decarboxylation aromatization reaction in the presence of a salt to form a compound of Formula (II), wherein R1 is H or alkyl, and R2 is alkyl:

Description

SYNTHESIS OF RENEWABLE TEREPHTHALATES AND AROMATIC DIISOCYANATES FROM MONOSACCHARIDES CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 718,489, filed on November 8, 2024, which is incorporated herein by reference in its entirety.FIELD

[0002] The present technology is generally related to the production of terephthalates and aromatic diisocyanates from monosaccharides using mild and scalable conditions.SUMMARY

[0003] In one aspect, a process for the production of a compound that includes subjecting a compound of Formula (I) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II). In such a process, the compound of Formula (I) and (II) may be represented as:where in these compounds, R1is H or alkyl; and R2is alkyl. According to some embodiments, the compound of Formula (I) may be prepared by contacting an esterified monosaccharide with a deoxydehydration catalyst to form a compound of Formula (III) (R1OC(O)C=CH-CH=C(O)COR1) and contacting the compound of Formula (III) with a compound of Formula (IV) (H2C=C(CO2H)(R2)) in the presence of a radical scavenger toform the compound of Formula (I). In some embodiments, the esterified monosaccharide is an esterified glucose, fructose, galactose, or mannose. In some embodiments, the esterified monosaccharide is an esterified galactose. In some embodiments, the process includes the use of graphite electrodes for carrying out the electrochemical decarboxylative aromatization reaction. In some such embodiments, the graphite electrodes are cylindrical graphite electrodes.

[0004] In another aspect, a process for the production of a diisocyanate of Formula (VI) is provided that includes subjecting a compound of Formula (I) (above) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II) (above), contacting the compound of Formula (II) with an azide forming reagent to form a compound of Formula (V), and heating the compound of Formula (V) to produce a compound of Formula (VI), where the compounds of Formula (V) and (VI) are represented as:

[0005] In another aspect, a process is provided for the production of a diolefinic diester and includes contacting an esterified monosaccharide of Formula (VII):with triethylorthoformate in the presence of p-toluenesulfonic acid followed by treatment with acetic anhydride to form a diolefin diester of Formula (III) (R1OC(O)C=CH-CH=C(O)COR1, wherein R1is alkyl).BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIGs. 1A and 1B show the cyclic voltammograms of substrates 4 and 5 in the absence and presence of 2.0 equiv. 2,4,6-collidine: A) Substrate 4 (Ep / 2= 1.31 V vs. Fc+ / 0); and A) Substrate 5 (Ep / 2= 1.23 V vs. Fc+ / 0), as well as the voltammograms for 2,4,6-collidine are also provided for comparison, according to the examples.DETAILED DESCRIPTION

[0007] Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s).

[0008] As utilized herein with respect to numerical ranges, the terms “approximately,” “about,” “substantially,” and similar terms will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the terms that are not clear to persons of ordinary skill in the art, given the context in which it is used, the terms will be plus or minus 10% of the disclosed values. When “approximately,” “about,” “substantially,” and similar terms are applied to a structural feature (e.g., to describe its shape, size, orientation, direction, etc.), these terms are meant to cover minor variations in structure that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0009] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0010] As used herein, “alkyl” groups include straight chain and branched alkyl groups having from 1 to about 20 carbon atoms, and typically from 1 to 12 carbons or, in some embodiments, from 1 to 8 carbon atoms. As employed herein, “alkyl groups” include cycloalkyl groups as defined below. Alkyl groups may be substituted or unsubstituted. Examples of straight chain alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branched alkyl groups include, but are not limited to, isopropyl, sec-butyl, t-butyl, neopentyl, and isopentyl groups. Representative substituted alkyl groups may be substituted one or more times with, for example, amino, thio, hydroxy, cyano, alkoxy, and / or halo groups such as F, Cl, Br, and I groups. As used herein the term haloalkyl is an alkyl group having one or more halo groups. In some embodiments, haloalkyl refers to a per-haloalkyl group.

[0011] Cycloalkyl groups are cyclic alkyl groups such as, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. In some embodiments, the cycloalkyl group has 3 to 8 ring members, whereas in other embodiments the number of ring carbon atoms range from 3 to 5, 6, or 7. Cycloalkyl groups may be substituted or unsubstituted. Cycloalkyl groups further include polycyclic cycloalkyl groups such as, but not limited to, norbornyl, adamantyl, bornyl, camphenyl, isocamphenyl, and carenyl groups, and fused rings such as, but not limited to, decalinyl, and the like. Cycloalkyl groups also include rings that are substituted with straight or branched chain alkyl groups as defined above. Representative substituted cycloalkyl groups may be mono-substituted or substituted more than once, such as, but not limited to: 2,2-; 2,3-; 2,4-; 2,5-; or 2,6-disubstituted cyclohexyl groups or mono-, di-, or trisubstituted norbornyl or cycloheptyl groups, which may be substituted with, for example, alkyl, alkoxy, amino, thio, hydroxy, cyano, and / or halo groups.

[0012] Alkenyl groups are straight chain, branched or cyclic alkyl groups having 2 to about 20 carbon atoms, and further including at least one double bond. In some embodiments alkenyl groups have from 1 to 12 carbons, or, typically, from 1 to 8 carbon atoms. Alkenyl groups may be substituted or unsubstituted. Alkenyl groups include, for instance, vinyl, propenyl, 2-butenyl, 3-butenyl, isobutenyl, cyclohexenyl, cyclopentenyl, cyclohexadienyl, butadienyl, pentadienyl, and hexadienyl groups among others. Alkenyl groups may be substituted similarly to alkyl groups. Divalent alkenyl groups, i.e., alkenyl groups with two points of attachment, include, but are not limited to, CH=CH-CH=CH2, C=CH2, or C=CHCH3.

[0013] As used herein, “aryl”, or “aromatic,” groups are cyclic aromatic hydrocarbons that do not contain heteroatoms. Aryl groups include monocyclic, bicyclic and polycyclic ring systems. Thus, aryl groups include, but are not limited to, phenyl, azulenyl, heptalenyl, biphenylenyl, indacenyl, fluorenyl, phenanthrenyl, triphenylenyl, pyrenyl, naphthacenyl, chrysenyl, biphenyl, anthracenyl, indenyl, indanyl, pentalenyl, and naphthyl groups. In some embodiments, aryl groups contain 6-14 carbons, and in others from 6 to 12 or even 6-10 carbon atoms in the ring portions of the groups. The phrase “aryl groups” includes groups containing fused rings, such as fused aromatic-aliphatic ring systems (e.g., indanyl, tetrahydronaphthyl, and the like). Aryl groups may be substituted or unsubstituted.

[0014] Diisocyanates (DI) are fundamental building blocks in the manufacturing process of a wide variety of polyurethane (PU) consumer products including flexible and rigid foams, CASE (coatings, adhesives, sealants, elastomers) polymers, and thermoplastics)11While both aromatic and aliphatic Dis find commercial applications, aromatic Dis are predominantly used on industrial scales owing to their favorable reaction kinetics and lower cost of production)21In particular, methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) are used in -90% of all industrial PU applications)31while less common Dis such as 1,4-phenylene diisocyanate (PPDI) find use in more specialized areas (Figure 1 A))41As high volume commodity chemicals, more than 10 million tons of aromatic Dis were produced globally in 2023 alone[5]- all of which were derived from petroleum sources)61Consequently, a viable and cost-effective route towards the synthesis of aromatic Dis from renewable feedstocks would be highly desirable.

[0015] In one aspect, a process for the production of a terephthalate includes subjecting a compound of Formula (I) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II). In the process, the compounds of Formula (I) and (II) are:In the above formulae, R1may be alkyl and R2may be H or alkyl. In some embodiments, R1may be Ci-Ce alkyl and R2may be H or Ci-Ce alkyl. In some embodiments, the compound of Formula (I) is the stereospecific compound of Formula (IA):

[0016] The electrochemical decarboxylative aromatization conversion of the compound of Formula (I) to that of Formula (II) may be conducted in an electrolyte solution containing a salt. Salts may include alkyl ammonium salts and / or perchlorate salts. Illustrative salt examples include, but are not limited to, tetrabutylammonium acetate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, tetrabutylammonium perchlorate, lithium perchlorate, sodium perchlorate, potassium perchlorate, and mixtures of any two or more thereof. Solvents for the electrolyte are not particularly limited, but illustrative solvents include, but are not limited to, acetonitrile, dichloromethane, acetone, and mixtures of any two or more thereof.

[0017] The electrochemical decarboxylative aromatization reaction may be conducted at about 20 mA and at 8.0 Faradays / mol.

[0018] Additionally, when converting the compound of Formula (I) to that of Formula (II), the process may be carried out in the presence of a base, such as a hindered pyridinyl base. Illustrative hindered pyridinyl bases include, but are not limited to, 2,6-lutidine and / or 2,4,6-collidine.

[0019] In some embodiments, the compound of Formula (I) is prepared by contacting an esterified monosaccharide with a deoxydehydration catalyst to form a compound of Formula (III) R1OC(O)C=CH-CH=C(O)COR1; and contacting the compound of Formula (III) with a compound of Formula (IV) H2C=C(CO2H)(R2) in the presence of a radical scavenger to form the compound of Formula (I). In such embodiments, R1and R2are as above, or in some embodiments, R1may be Ci-Ce alkyl and R2may be H or Ci-Ce alkyl, or in further embodiments, R1and R2may individually be methyl or ethyl. In some embodiments, the esterified monosaccharide is an esterified glucose, fructose, galactose, or mannose. In some embodiments, the esterified monosaccharide is an esterified galactose.

[0020] According to various embodiments, when converting the compounds of Formulae (III) and (IV) to that of Formula (I), the radical scavenger may be a hydroquinone. Additionally, it may be conducted without solvent.

[0021] As used herein, an esterified monosaccharide may be an esterified glucose, fructose, galactose, or mannose. In some embodiments, the esterified monosaccharide is an esterified galactose, and the esterified galactose is a compound that is derived from D-galactose:Sources of D-galactose include, but are not limited to galactans such as hemicellulose and algae; sugar beets; and pectin. The derivation of the D-galactose is conducted byoxidizing the D-galactose to mucic acid using nitric acid and catalytic amounts of sodium nitrite, followed by an esterification reaction with an alcohol (e.g. ethanol). The conversion of the mucic acid to the diolefin of Formula (III) may be accomplished in the presence of a transition metal catalyst, or under transition metal-free conditions.

[0022] In other aspects, the compound of Formula (I) may be used to prepare diisocyanates of Formula (VI):wherein R2is alkyl. The process of preparing the diisocyanates includes subjecting a compound of Formula (I) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II); contacting the compound of Formula (II) with an azide forming reagent to form a compound of Formula (V); and heating the compound of Formula (V) to produce the diisocyanate of Formula (VI); wherein the compound of Formula (V) is:

[0023] The diisocyanate may be used in other reactions to form urethanes, ureas, and the like. One advantage of the proposed process for the diisocyanate formation is thatit eliminates the use of phosgene and the preparation of a variety of substituted aromatic diisocyanates is facilitated.

[0024] The present invention, thus generally described, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.EXAMPLES

[0025] Dis are industrially synthesized from their diamine precursors via treatment with phosgene gas at elevated temperatures.[7]Although an efficient process, phosgene is a highly toxic[8]and heavily regulated reagent, requiring specialized equipment for in situ generation and use at select DI manufacturing sites.[9]Accordingly, several phosgene-free routes towards Dis have been developed on lab-scale, with emphasis being placed on minimizing hazards while implementing the use of renewable feedstocks.[2]In this context, significant efforts have been made towards the development of renewable Dis via phosgene-free routes from a variety of sources including fatty acids,

[0010] algae oil,

[0011] lignin,

[0012] amino acids,

[0013] and saccharides,

[0014] among others. Their synthesis can be achieved through various approaches; however, the Curtius rearrangement

[0016] of carboxylderived acyl azides offers a scalable approach owing to the ubiquity of carboxylic acid functionality in biological precursors.

[0015] For example, a scalable route towards DIs in continuous flow has been described via the Curtius rearrangement that utilizes both aromatic and aliphatic dicarboxylic acid starting materials.

[0011] Using this route, several biomass-derived aliphatic Dis have been synthesized and applied to the preparation of high-performance thermoplastic polyurethanes (TPUs) with up to 100% renewable carbon content.

[0016] The use of flow chemistry is essential to the scalability of this process, as it allows safe handling of the in situ generated, highly reactive acyl azide intermediate in a controlled environment.

[0026] While promising, these examples have focused primarily on the synthesis of renewable aliphatic Dis, with little to no progress being made on the development of their aromatic counterparts, for which there is high demand.[2, 17]With the exception of lignin,

[0018] this is largely due to the lack of routes toward functionalized benzene derivatives, such as terephthalates, sourced from biomass.

[0019] Although several routes have been proposed, none have proven practical at scale.

[0020] As the most direct and atom-economical way to access terephthalates from biomass, many have employed Diels-Alder (DA) reactions between conjugated dienes and suitable dienophiles)

[0019] Commonly, renewable furan-based dienes such as 2,5-dimethylfuran)

[0021] furfural)

[0022] and furan dicarboxylic acid (FDCA) or its more soluble diester

[0023] are used in conjunction with ethylene gas as a dienophile to afford aromatics through a tandem DA / dehydration reaction. However, in the case of 2, 5 -dimethylfuran and furfural, further oxidation steps are required to install the carboxylic acid groups, while the FDCA route requires extremely forcing reaction conditions to proceed with high pressures of ethylene gas (upwards of 60 bar) and temperatures exceeding 250 °C, even in the presence of designer catalysts)191

[0027] Alternatively, biomass-derived trans,trans-muconic acid (ttMA)

[0024] has proven to be a promising feedstock for the synthesis of terephthalates via DA chemistry. Through a three-step sequence, / / MA is first esterified to its more soluble diester in situ before cycloaddition with ethylene occurs in the presence of catalytic amounts of tungstosilicic acid. Dehydrogenation at elevated temperatures using Pd / C then affords diethyl terephthalate. Although this highlights the potential of this route towards renewable terephthalates, elevated temperatures (200 °C) and high pressures of ethylene gas (>20 bar) are required to achieve the cycloaddition, which limit the scalability of the process. Similar to FDCA, ttMA is strongly deactivated towards DA cycloaddition owing to the presence of two electron-withdrawing substituents)

[0025] Therefore, when coupled with a non-activated dienophile such as ethylene, high temperatures and pressures are required to overcome thermodynamic and kinetic barriers to achieve cycloaddition.

[0028] The use of acrylates (such as acrylic acid) as ethylene surrogates in reactions with ttMA diesters offers an attractive alternative to construct terephthalates. Notably, acrylic acid is more reactive, easier to handle, and can be derived from biomass in higher yields than ethylene)

[0015] Furthermore, the appended carboxylic acid could be used as a functional handle to aid in the subsequent dehydrogenation process through a decarb oxy lative olefination approach in lieu of Pd / C. With this in mind, we envisioned a path to renewable aromatic Dis from D-galactose, which proceeds through a cyclohexene carboxylic acid intermediate derived from the DA reaction between acrylates and / / MA diesters. Of particular importance was the development of a suitable route which avoided the use of high-pressure gases, costly transition metals, and had the potential for futurescale-up. Herein, we report an alternative route to renewable terephthalates and aromatic Dis from D-galactose featuring a key electrochemical decarboxylative aromatization sequence. An illustration of the process is shown in Scheme 1:Scheme 1:D [decagram scale]

[0029] Starting from D-galactose, mucic acid may be obtained via oxidation with nitric acid and catalytic amounts of sodium nitrite, as shown below in Scheme 2. It is worth noting that these harshly oxidizing conditions, while not without their drawbacks, remain the most widely employed to synthesize mucic acid on industrial scales)271To increase solubility, mucic acid was then esterified under standard Fischer esterification conditions to afford diethyl mucate 2 in a 79% yield over two steps. Initially, we planned to use well-known rhenium-catalyzed deoxydehydration (DODH) conditions1281to synthesize / / MA diesters from 2; however, we recognized this could prove cost-prohibitive on scale. While efficient in practice, rhenium is one of the rarest elements on earth, requiring both cost and labor intensive methods of extraction and purification)291Conversely, numerous transition-metal free DODH transformations for the conversion of bio-derived polyols to their corresponding alkenes have been reported, such as glycerol, erythritol, and quinic acid, to name a few)301Typical conditions for these substrates involve the use of orthoformates with catalytic amounts of formic acid at elevated temperatures, leading to CO2release that drives olefin bond formation)301Scheme 2:

[0030] Modified Eastwood olefination

[0031] conditions may be applied to 2 to generate muconate diester 3 in a one-pot, two-step process. Upon further heating in the presence of AC2O, ethoxide is eliminated as EtOAc, followed by release of acetic acid and CO2.

[0033] This was later confirmed through isolation and characterization of 2a. Addition of catalytic p-toluenesulfonic acid was found to significantly improve the formation of 2a, and is believed to reverse lactone formation when 2 is subjected to heating.

[0034] Notably, the reaction proceeds under solvent-free conditions on decagram lab scale without the use of transition-metals to provide ample quantities of 3.

[0031] DA cycloaddition between ffMA and acrylic acid has been demonstrated on gram scale under solvent-free conditions at 140 °C, although no yields or characterization data were provided. Using modified conditions, it has been found that 3 readily underwent DA cycloaddition with both acrylic acid and methacrylic acid to afford 4 (8: 1 endo:ex ) and 5 (>99: 1 endo:ex ) in good yields without the use of solvents and in short time frames. To suppress undesired polymerization, hydroquinone may be used as a free radical scavenger, which was crucial to drive the DA conversion to >98%. It was found that these reactions could be run either in sealed pressure tubes or round-bottomed flasks fitted with condensers without any significant changes in yield.

[0032] Constant current (CC) electrolysis was employed in favor of constant potential, while graphite electrodes were selected based on their established efficacy in generating carbocations through further oxidation of the carbon-centered radical intermediates produced upon oxidative decarboxylation.

[0037] Initial attempts revealed minor amounts (<10%) of the desired aromatized products 6 and 7 in the crude1H NMR spectra (Scheme 3). A general screen of solvents, bases, electrolytes, and additivesultimately led to significant improvements in yield when using redox-inactive tetrabutylammonium hexafluorophosphate electrolyte systems. In contrast, use of tetrabutylammonium bromide generated complex reaction mixtures with no desired product being observed (entry 5). Perchlorate salts, which are known to favor carbocation formation in Hofer-Moest reactions,

[0038] delivered further increases in yield (entries 6 and 7), with lithium perchlorate in DCM / acetone affording terephthalates 6 and 7 in 58% and 64% yield, respectively (entry 8). Using these conditions under open air, a drastic decrease in yield was observed for both 6 and 7 (entry 9). Employing conditions in entry 8, gram-scale reactions were conducted without significant loss in efficiency.Scheme 3:

[0033] Mechanistically, the process is believed to proceed through initial carboxylate oxidation to a carboxyl radical, supported by cyclic voltammetry studies which show anodic oxidation events for 4 and 5 at half peak potentials (Ep / 2) of 1.31 V and 1.23 V (vs. Fc+ / 0), respectively, only in the presence of 2,4,6-collidine. Subsequent decarboxylation, one-electron oxidation, and deprotonation presumably generates a mixture of 1,4- and 1,3 -cyclohexadienes, which can undergo further oxidation to a radical cation. Successive deprotonation and oxidation leads to a carbocation intermediate which, upon final deprotonation, affords the desired aromatized product 6 or 7. The intermediacy of a similar cyclohexadiene-derived radical cation species has been proposed in a previous example of electrochemical dehydrogenative aromatization.

[0039]

[0034] Having established a reliable set of conditions for the decarboxylative aromatization of 4 and 5, terephthalates 6 and 7 were readily converted into theircorresponding diacyl hydrazides with hydrazine hydrate in refluxing ethanol.

[0040] Finally, using flow chemistry,

[0011] diacyl hydrazides 8 and 9 were converted to Dis 10 and 11 through a two-step telescoped process (see SI for details). Proper handling and purification of the crude reaction streams was found to significantly enhance the isolated yields (see SI), as aromatic Dis are highly electrophilic species, showing reaction rate constants 400-fold greater than aliphatics.

[0041] Following purification, 11 was used to synthesize a thermoplastic PU (TPU) by mixing with a fully renewable polyester polyol, 1,4-butanediol (1,4-BDO) as a chain extender, and catalyst (see Scheme 4). In parallel, a TPU was prepared using commercially available 2,4-TDI with the same formulation for comparison purposes. Comparing the resulting material and thermal properties, the TPU made with fully renewable 11 was nearly identical to that sourced from D-galactose.Changing the regiochemistry of the DI from 2,4 to 2,5 increased Shore A hardness by more than 20 units. In our experience, such TPU metrics can be tailored for specific applications by formulation modifications.Scheme 4:

[0035] Alternatively, the crude reaction streams from the flow system could be quenched with aqueous HCI to generate the corresponding diamines (12, 13), which were isolated following a basic workup. Aromatic diamines, like Dis, are high-value commodity chemicals used to manufacture polyamides and are almost exclusively derived from petroleum resources today.

[0042] Diamine 12 is of particular interest, as it is a main component of Kevlar, an ultra-strong and heat-resistant fiber.

[0043] As such, this process demonstrates an alternative route towards their synthesis from renewable feedstocks.

[0036] In summary, a transition-metal free synthesis of renewable terephthalates, aromatic Dis, and aromatic diamines is presented. In contrast to existing routes towards renewable terephthalates, this process avoids the use of high-pressure gases and reaction vessels, while demonstrating the efficiency of an innovative electrochemicaldecarb oxy I ative aromatization sequence. While this study serves as a proof-of-principle for this transformation on gram-scale, future work in our lab is aimed at translating this into a continuous flow process.

[0044] Following a two-step, phosgene-free process, these renewable terephthalates were converted to Dis in flow, which were subsequently used to synthesize a TPU with commercially relevant material properties comparable to those from petroleum derived equivalents. More broadly, this work establishes the potential to prepare fully renewable commodity chemicals and materials from sustainable sources.

[0037] General Experimental. Chemical reagents were purchased from Sigma Aldrich, Fischer Scientific, TCI Chemicals, Alfa Aeser or MP Biomedicals. All chemicals were reagent grade and were used as is without further purification, unless otherwise noted. Deuterated solvents (CDCl3and d6-DMSO) were purchased from Cambridge Isotope Laboratories.1H NMR and13C NMR spectra were recorded on a JEOL ECA 400 MHz spectrometer. FT-IR was recorded using a Thermo Scientific Nicolet™ iS20 spectrometer (16 scans taken for each sample). High-Resolution Mass Spectrometry was conducted using a Thermo Scientific LTQ Orbitrap XL mass spectrometer. High-pressure HPLC pumps and the Binary Pump system equipped with 50 mL / min pump heads and the heated coil reactor were purchased from Uniqsis. The 8 mL glass plate microreactor was purchased from the Little Things Factory. Backpressure regulators were purchased from IDEX Health and Science Technologies. Reactors were constructed from polytetrafluoroethylene (PTFE) tubing with either a 1 / 16” outer diameter and 1 / 32" inner diameter, or 1 / 8” outer diameter and 1 / 16” inner diameter with complementary PEEK fittings. The system was controlled using Uniqsis FlowControl™ software.Electrochemical experiments were conducted using a SKY TOPPOWER 30V, 5 A (PS305H) benchtop DC power supply and cylindrical graphite electrodes.

[0038] Compound SI - mucic acid:Mucic acid was synthesized following a slightly modified procedure reported by Pigman and co-workers.

[0045] To a 500 mL 2-neck round-bottomed flask equipped with a condenser was added 150 mL of concentrated HNO3, followed by the addition of anhydrous D-(+)-galactose (60 g, 334 mmol, 1.0 equiv.). The mixture was stirred at room temperature for 20 minutes to ensure complete dissolution and was then cooled in an ice bath. Sodium nitrite (3.46 g, 50 mmol, 0.15 equiv.) was added portion-wise over the course of 2 hours to the reaction which was accompanied by the evolution of NO2 gas (it is crucial to ensure that the reaction mixture is maintained in an ice bath during the first 2 hours of the reaction). The resulting evolved NO2 gas was bubbled into an aqueous solution of NaOH (500 mL, 1M) through tubing secured at the top of the reflux condenser. We note that the oxidation is exothermic and extra care should be taken to ensure the reaction mixture is kept in an ice bath. After 3 hours in an ice bath, the mixture is allowed to warm to room temperature and stirred for 21 hours. The resulting slurry is filtered, washed with water (250 mL), and dried. The crude solid is then triturated in hot methanol (250 mL), filtered and dried to afford mucic acid (SI) (58.6 g, 278 mmol, 84%) as a white powder. Spectral data matches that which has been previously reported)271*Note: this reaction is exothermic, especially during the first 2 hours. We note that extra care should be taken when running this reaction. The reaction mixture needs to be cooled (and kept cool) adequately during the first 2 hours of the reaction. The reaction should only be run in a well-ventilated hood. Physical state: white powder. IR (neat) v = 3280, 2960, 1718, 1298, 1238, 1114, 1058 cm’1.1H NMR (400 MHz, DMSO-d6) δ 12.48 (bs, 2H), 4.64 (bs, 4H), 4.22 (s, 2H), 3.77 (s, 2H).13C NMR (100 MHz, DMSO-d6) δ 175.9, 71.8, 70.3.

[0039] Compound 2 - diethyl mucate:SI (58 g, 276 mmol, 1.0 equiv.) was suspended in 600 mL of EtOH in a 1 L round bottomed flask equipped with a stir bar. H2SO4 (2.96 mL, 55.2 mmol, 0.2 equiv.) was slowly added, the flask was equipped with a condenser, and the mixture was refluxed for 18 hours. After cooling to room temperature, the mixture was placed in the freezer for 2hours. The resulting white solid was isolated via vacuum filtration and washed with cold EtOH (100 mL x2). The filtrate was concentrated on a rotary evaporator to yield an off-white slurry which was recrystallized from EtOH to afford a white solid upon cooling and collected via vacuum filtration. The collected white solid portions were combined and dried further under vacuum filtration to afford 2 (69.1 g, 260 mmol, 94%). Physical state: white, fluffy crystals. IR (neat) v = 3276, 2988, 1720, 1236, 1113, 1046, 1016 cm’1.1H NMR (400 MHz, DMSO-d6) δ 4.87 (d, J= 8.0 Hz, 2H), 4.84 - 4.77 (m, 2H), 4.29 (d, J = 1.1 Hz, 2H), 4.10 (qd, J= 7.1, 4.2 Hz, 4H), 3.82 - 3.74 (m, 2H), 1.20 (t, J= 7.1 Hz, 6H).13C NMR (100 MHz, DMSO-d6) δ 174.2, 71.8, 70.7, 60.7, 14.7. HRMS (ESLTOF) m / z: calc’d for CioHisOsNa [M + Na]+289.0894, found 289.0896.

[0040] Compound 3 - trans, trans-di ethyl muconate:The reaction was run according to a slightly modified procedure reported by Eastwood and coworkers

[0031] and Takase and coworkers.

[0046] To a 250 mL round bottomed flask was added 2 (40 g, 151 mmol, 1.0 equiv.), followed by the addition of triethyl orthoformate (51.3 mL, 309 mmol, 2.05 equiv.), p-toluenesulfonic acid monohydrate (1.43 g, 7.53 mmol, 0.05 equiv.) and a stir bar. A short-path distillation head was fixed to the flask and the mixture was heated with stirring to 95 °C (the diester began to solubilize around 90 °C). The mixture was stirred at 95 °C for 1.5 hours during which time some EtOH and small amounts of ethyl formate (reaction of TEOF with residual water) distilled out of the mixture and was collected. The mixture was then heated to 110 °C and stirred at this temperature for 2 hours. Bisorthoester 2a was isolated via dissolving a small amount of the crude mixture in DMSO and pouring the solution into cold DI water. 2a was isolated as white, needle-like crystals after filtration and drying (see below for characterization data). The crude reaction mixture was then allowed to cool to room temperature, and then acetic anhydride (40 mL) was added, and the mixture was refluxed at 145 °C for 4 hours. After 4 hours, the mixture was cooled to room temperature to afford an orange solution which was dissolved in EtOAc (150 mL), washed with saturated NaHCCh (100 mL), DIwater (2 x 100 mL), and then concentrated to afford a light-yellow pasty solid. The crude mixture was purified via silica gel chromatography eluting 9:1 hexanes / EtOAc to provide 3 (20.3 g, 102.4 mmol, 68%) as white crystals. Spectral data for 3 matches that which has been previously reported)471Characterization data for Compound 2a: Physical state: white, needle-like crystals. IR (neat) v = 2982, 2938, 2908, 1742, 1100, 1054, 1017, 946 cm-1.1H NMR (400 MHz, CDCl3) δ 6.06 (s, 2H), 4.83 (dd, J= 1.7, 1.1 Hz, 2H), 4.45 (dd, J= 1.7, 1.1 Hz, 2H), 4.25 (qd, J= 7.1, 2.0 Hz, 4H), 3.68 (qd, J= 7.1, 2.7 Hz, 4H), 1.30 (t, J= 7.1 Hz, 6H), 1.23 (t, J= 1A Hz, 6H).13C NMR (100 MHz, CDCl3) δ 169.8, 117.4, 78.7, 76.3, 61.9, 61.3, 15.0, 14.2. HRMS (ESI-TOF) m / z: calc’d for Ci6H260ioNa [M + Na]+401.1418; found 401.1419.

[0041] Characterization data for Compound 3: Physical state: white crystals. Rr 0.38 (9:1 hexanes / EtOAc). IR (neat) v = 3067, 2979, 1696, 1609, 1237, 1153, 1019, 860 cm’1.XH NMR (400 MHz, CDCh) 67.35 - 7.26 (m, 2H), 6.25 - 6.10 (m, 2H), 4.23 (q, J= 7.2 Hz, 4H), 1.30 (t, J= 7.1 Hz, 6H).13C NMR (100 MHz, CDCl3) δ 166.0, 140.9, 128.5, 61.0, 14.3. HRMS (ESI-TOF) m / z: calc’d for C10H15O4 [M + H]+199.0965, found 199.0964.

[0042] Compound 4 - acrylic acid cyclohexene adduct:To a 15 mL pressure tube was added 3 (8.5 g, 42.9 mmol, 1.0 equiv.), hydroquinone (472 mg, 4.3 mmol, 0.1 equiv.), freshly distilled acrylic acid (7.35 mL, 107.2 mmol, 2.5 equiv.), and a stir bar. Upon addition of acrylic acid, 3 fully solubilizes after stirring at room temperature for 5 minutes. The reaction mixture was sealed and heated to 130 °C for 4 hours, and then cooled to room temperature. The resulting mixture was dissolved in EtOAc (150 mL) and then washed with DI water (3 x 100 mL). The organic phase was then washed with a saturated solution of NaHCCh (100 mL). The aqueous phase was then washed with EtOAc (50 mL x 2), and then acidified to -pH 3 with 2 M HC1. Theacidified phase was then extracted with EtOAc (3 x 50 mL) and concentrated to a yellow oil. Purification via silica gel chromatography eluting hexanes / EtOAc / AcOH (65 / 34 / 1) afforded 4 (9.38 g, 34.7 mmol, 81%) as a mixture of diastereomers (~8:1 endo:exo) as a viscous pale-yellow oil. The mixture was dried under vacuum for 4 hours to afford a pasty -white solid which could be further washed with hot hexanes and dried to afford a pure sample of the endo diastereomer as a white crystalline solid. Efforts towards isolating a pure sample of the exo product were met with difficulty and abandoned.Physical state: viscous pale-yellow oil as mixture, endo diastereomer: white crystalline solid. Rf0.22 (65:35 hexanes / EtOAc), visualized with KMnO4developing stain. IR (neat) v = 3279, 2982, 1726, 1699, 1186, 1114 cm’1.1H NMR - 8:1 mixture (400 MHz, CDCl3) δ 6.05 - 5.93 (m, 2H), 4.18 - 4.09 (m, 4H), 3.59 - 3.53 (endo, m, 1H), 3.50 (exo, dd, J= 7.8, 2.1 Hz, 0.13H), 3.25 - 3.22 (exo, m, 0.13H), 3.2 - 3.14 (endo / exo overlap, m, 1.13H), 2.77 - 2.64 endo, m, 1H), 2.55 - 2.48 endo, m, 1H), 2.38 (exo, dd, J= 13.5, 8.2 Hz, 0.13H), 2.24 - 2.15 endo, m, 1H), 2.02 - 1.94 (exo, m, 0.13H), 1.28-1.21 (dt, J= 11.0, 7.1 Hz, 6H).1H NMR - endo (400 MHz, CDCl3) δ 6.01 (dq, J= 9.8, 1.7 Hz, 1H), 5.94 (ddd, J= 10.0, 5.1, 2.7 Hz, 1H), 4.14 (dq, J= 10.2, 7.2 Hz, 4H), 3.56 (dp, J= 6.6, 2.0 Hz, 1H), 3.16 (ddq, J= 11.0, 5.3, 2.5 Hz, 1H), 2.69 (ddd, J= 12.5, 5.4, 3.0 Hz, 1H), 2.57 -2.47 (m, 1H), 2.24 - 2.12 (m, 1H), 1.24 (dt, J= 11.0, 7.1 Hz, 6H).13C NMR - endo (100 MHz, CDCl3) δ 178.4, 172.8, 171.1, 127.9, 125.0, 61.2, 61.1, 42.0, 41.9, 40.2, 23.5, 14.3, 14.1. HRMS (ESI-TOF) m / z: calc’d for CnHisOeNa [M + Na]+293.0996, found 293.0996.

[0043] Compound 5 - methacrylic acid cyclohexene adduct:To a 15 mL pressure tube was added 3 (8.5 g, 42.9 mmol, 1.0 equiv.), hydroquinone (472 mg, 4.3 mmol, 0.1 equiv.), methacrylic acid (8.8 mL, 107.2 mmol, 2.5 equiv.), and a stir bar. Upon addition of methacrylic acid, 3 fully solubilizes after stirring at room temperature for 5 minutes. The reaction mixture was sealed and heated to 140 °C for 8hours, and then cooled to room temperature. The resulting mixture was dissolved in EtOAc (100 mL) and then washed with DI water (3 x 100 mL). The organic phase was then washed with a saturated solution of NaHCCh. The aqueous phase was then washed with EtOAc (50 mL x 2), and then acidified to -pH 3 with 2 M HC1. The acidified phase was then extracted with EtOAc (3 x 50 mL) and concentrated to a yellow oil. Purification via silica gel chromatography eluting hexanes / EtOAc (65 / 35) afforded 5 as a single diastereomer (9.02 g, 31.7 mmol, 74%) as a viscous pale-yellow oil which solidified into a pale-yellow / white solid under vacuum. Physical state: viscous milky / pale yellow oil, solidifies into pale-yellow / white solid. Rr 0.35 (65:35 hexanes / EtOAc), visualized with KMnO4developing stain. IR (neat) v = 3276, 2981, 1704, 1185, 1109, 1033 cm’1.1H NMR (400 MHz, CDCl3) δ 6.03 - 5.93 (m, 1H), 5.83 (ddd, J= 10.0, 5.5, 2.8 Hz, 1H), 4.13 (dq, J= 19.1, 7.1 Hz, 4H), 3.28 - 3.15 (m, 1H), 3.11 (ddt, J= 11.6, 6.1, 2.6 Hz, 1H), 2.37 (dd, J= 13.8, 11.7 Hz, 1H), 2.29 -2.17 (m, 1H), 1.31 - 1.17 (m, 9H).13C NMR (100 MHz, CDCl3) δ 182.6, 173.3, 171.6, 126.7, 123.9, 61.12, 61.10, 48.2, 42.3, 39.3, 28.2, 22.7, 14.3, 14.1. HRMS (ESI-TOF) m / z: calc’d for Ci4H2o06Na [M + Na]+307.1152, found 307.1153.

[0044] Compound 6 - diethyl terephthalate:To a 20 mL scintillation vial containing a stir bar, was added 4 (135 mg, 0.5 mmol, 1.0 equiv,), 2,4,6-collidine (132 μL, 1 mmol, 2.0 equiv.), and lithium perchlorate (85 mg, 0.8 mmol, 0.1 M). Acetone (4 mL), and DCM (4 mL) were then added to the vial which was stirred for 5 minutes until complete dissolution of lithium perchlorate. The solution was then degassed with an argon balloon for 5 minutes and promptly sealed with the custom cap equipped with two cylindrical graphite electrodes (6 mm diameter, 70 mm in length). The mixture was then electrolyzed under constant current (20 mA, 8.0 F / mol). After completion of the reaction, the electrodes were rinsed with acetone, and the solvent was removed. The resulting solid mixture was dissolved in EtOAc (15 mL), washed with 0.5M HC1 (15 mL) and brine (15 mL), and then concentrated. The crude mixture was then purified via silica gel chromatography eluting hexanes / EtOAc (95 / 5) to afford 6 (64 mg, 0.29 mmol, 58%) as a white, slightly yellow powder. Physical state: white, slightly yellow powder. Rr: 0.51 (9:1 hexanes / EtOAc). IR (neat) v = 2989, 2941, 1713, 1266, 1244, 1101, 1020 cm’1.1H NMR (400 MHz, CDCl3) δ 8.09 (s, 4H), 4.40 (q, J = 7.2 Hz, 4H), 1.41 (t, J = 7.2 Hz, 6H).13C NMR (100 MHz, CDCl3) δ 166.0, 134.2, 129.6, 61.5, 14.4. HRMS (ESI-TOF) m / z: calc’d for C12H15O4 [M + H]+223.0965, found 223.0963.

[0045] Gram-scale synthesis of 6: To a 250 mL glass jar containing a stir bar, was added 4 (3.24 g, 12 mmol, 1.0 equiv,), 2,4,6-collidine (2.77 mL, 24 mmol, 2.0 equiv.), and lithium perchlorate (2.44 g, 23 mmol, 0.1 M). Acetone (115 mL), and DCM (115 mL) were then added to the jar which was stirred for 5 minutes until complete dissolution of lithium perchlorate. The solution was then degassed with an argon balloon for 10 minutes and promptly sealed with a custom rubber cap equipped with two cylindrical graphite electrodes (8 mm diameter, 140 mm in length) and needle. The mixture was then electrolyzed under constant current (80 mA, 10 F / mol) and was monitored via TLC throughout. After completion of the reaction, the electrodes were rinsed with acetone, and the solvent was removed. The resulting orange viscous oil was dissolved in EtOAc (75 mL), washed with 0.5 M HC1 (50 mL) and brine (50 mL), and then concentrated. The crude mixture was then purified via silica gel chromatography eluting hexanes / EtOAc (95 / 5) to afford 7 (1.25 g, 5.64 mmol, 47%). Reactions above 12 mmol scale were attempted and met with difficulty as significant drops in yield (<30%) were observed, even upon increasing equivalents of electrons and applied current. As such, two identical reactions were run in parallel as described above to prepare enough material. We suspect the drop in yield on larger scales was due to a lack of available electrode surface area for necessary oxidation events to occur - a common issue when scaling electrochemistry in batch.

[0048]

[0046] Compound 7 - diethyl 2-methylterephthalate:To a 20 mL scintillation vial containing a stir bar, was added 5 (142 mg, 0.5 mmol, 1.0 equiv,), 2,4,6-collidine (132 μL, 1 mmol, 2.0 equiv.), and lithium perchlorate (85 mg, 0.8 mmol, 0.1 M). Acetone (4 mL), and DCM (4 mL) were then added to the vial which was stirred for 5 minutes until complete dissolution of lithium perchlorate. The solution was then degassed with an argon balloon for 5 minutes and promptly sealed with a custom cap equipped with two cylindrical graphite electrodes (6 mm diameter, 70 mm in length). The mixture was then electrolyzed under constant current (20 mA, 8.0 F / mol). After completion of the reaction, the electrodes were rinsed with acetone, and the solvent was removed. The resulting solid mixture was dissolved in EtOAc (15 mL), washed with 0.5 M HCl (15 mL) and brine (15 mL), and then concentrated. The crude mixture was then purified via silica gel chromatography eluting hexanes / EtOAc (95 / 5) to afford 7 (76 mg, 0.32 mmol, 64%) as a pale-yellow oil. Physical state: pale yellow oil. Rr 0.59 (9:1 hexanes / EtOAc). IR (neat) v = 2959, 2650, 1718, 1686, 1298, 1258, 1191, 1110, 1082, cm’1.1H NMR (400 MHz, CDCl3) δ 7.96 – 7.84 (m, 3H), 4.38 (qd, J = 7.2, 4.3 Hz, 4H), 2.62 (s, 3H), 1.40 (td, J = 7.1, 0.8 Hz, 6H).13C NMR (100 MHz, CDCl3) δ 167.2, 166.1, 140.0, 134, 133.1, 132.6, 130.5, 126.7, 61.4, 61.2, 21.6, 14.3. HRMS (ESLTOF) m / z: calc’d for C13H17O4 [M + H]+237.1121, found 237.1117.

[0047] Gram-scale synthesis of 7: To a 250 mL glass jar containing a stir bar, was added 5 (2.56 g, 9 mmol, 1.0 equiv,), 2,4,6-collidine (2.08 mL, 18 mmol, 2.0 equiv.), and lithium perchlorate (2.44 g, 23 mmol, 0.1 M). Acetone (115 mL), and DCM (115 mL) were then added to the jar which was stirred for 5 minutes until complete dissolution of lithium perchlorate. The solution was then degassed with an argon balloon for 10 minutes and promptly sealed with a custom rubber cap equipped with two cylindrical graphite electrodes (8 mm diameter, 140 mm in length) and needle. The mixture was then electrolyzed under constant current (80 mA, 10 F / mol) and was monitored via TLCthroughout. After completion of the reaction, the electrodes were rinsed with acetone, and the solvent was removed. The resulting orange viscous oil was dissolved in EtOAc (75 mL), washed with 0.5 M HC1 (50 mL) and brine (50 mL), and then concentrated. The crude mixture was then purified via silica gel chromatography eluting hexanes / EtOAc (95 / 5) to afford 7 (1.21 g, 5.1 mmol, 57%).Reactions above 10 mmol scale were attempted and met with difficulty as described above for the gram-scale synthesis of 6 which resulted in the requirement for two identical reactions to be run in parallel.

[0048] Compound 8 - terephthalic dihydrazide:$ «To a 25 mL round bottomed flask was added 6 (2.40 g, 10.8 mmol, 1.0 equiv.) and 15 mL of EtOH. Hydrazine monohydrate (3.2 mL, 65 mmol, 6.0 equiv.) was carefully added to the mixture which was then heated to reflux for 18 hours. During the course of the reaction, an off-white solid slowly precipitated out of solution. After 18 hours, the mixture consisting of a white solid suspended in a light-yellow solution was cooled to room temperature and placed into a freezer for 2 hours. The solid was isolated via vacuum filtration and washed with EtOH (25 mL x2) and DI water (25 mL) and further dried to afford 8 (1.83 g, 9.4 mmol, 87%) as a white powder. Physical state: white powder. IR (neat) v = 3312, 3034, 1603, 1539, 1488, 1338, 923 cm’1.XH NMR (400 MHz, DMSO-£>6) 69.88 (s, 2H), 7.87 (s, 4H), 4.54 (s, 4H).13C NMR (100 MHz, DMSO-6) δ 165.7, 136.0, 127.5. HRMS (ESI-TOF) m / z: calc’d for C8H11N4O2 [M + H]+195.0877, found 195.0877.

[0049] Compound 9 - 2-methylterephthalic dihydrazide:The reaction was conducted in identical fashion as described above using 7 (2.35 g, 9.94 mmol, 1.0 equiv.), hydrazine monohydrate (2.9 mL, 59.6 mmol, 6.0 equiv.), and 10 mL of EtOH to afford 9 (1.88 g, 9.05 mmol, 91%) as a white powder. Physical state: white powder. IR (neat) v = 3366, 3305, 3280, 3212, 1720, 1626, 1518, 1305, 1259, 1083, cm’1.1H NMR (400 MHz, DMSO-6) δ 9.76 (s, 1H), 9.45 (s, 1H), 7.65 (d, J = 1.8 Hz, 1H), 7.60 (dd, J = 7.9, 1.8 Hz, 1H), 7.28 (d, J = 7.9 Hz, 1H), 4.45 (s, 4H), 2.31 (s, 3H).13C NMR (100 MHz, DMSO-6) δ 168.4, 165.9, 138.6, 136.2, 134.5, 129.5, 127.8, 124.6, 19.9. HRMS (ESI-TOF) m / z: calc’d for C9H13N4O2 [M + H]+209.1033, found 209.1034.

[0050] Compound 10 - 1,4-phenylene diisocyanate:Compound 10 was synthesized using a slightly modified procedure reported by our group using the flow system depicted above.

[0011] Briefly, 150 mL of DI water was added to a 250 mL Erlenmeyer flask, followed by the addition of 8 (1.80 g, 9.27 mmol, 1.0 equiv.), and concentrated HC1 (1.58 mL, 2.1 equiv.) and the solution was stirred at room temperature for 5 minutes until complete dissolution of 8 (Pump 3 solution). In a separate flask, NaNO2(1.41 g, 20.4 mmol, 2.2 equiv.) was dissolved in 150 mL of DI water (Pump 1 solution). Pump 2 solution consisted of a 50 / 50 mixture of toluene / MTBE. Pumps 1, 2, and 3 were operated at rates of 2 mL / min and were fed into an 8 mL glass plate microreactor (Little Things Factory), and then into a continuous liquid / liquid centrifugalseparator (Rousselet Robatel). At a rate of 2 mL / min, Pump 4 fed the crude organic-phase mixture through a glass column packed with Na2SO4, and then into a heated coil reactor set to 130 °C. The output feed was then concentrated on a rotary evaporator to afford crude 10 as a yellow solid which was purified immediately (see below).

[0051] Purification: Aromatic diisocyanates are highly reactive compounds.Industrially, they are purified via distillation under stringent conditions. However, given the small scale of reactions, we reasoned that distillation was not the best course of action. Initial attempts at purification via silica gel chromatography were met with difficulty as 10 rapidly decomposed on silica gel and <25% of mass was recovered, even on short silica gel plugs with under vacuum. We were pleased to find that 10 could be isolated selectively form the crude reaction mixture through extraction, filtration of the insoluble impurities, and then concentration using DCM. Following purification, 10 ( 985 mg, 5.65 mmol, 61%) was isolated as a pale-yellow powder. Physical state: pale-yellow powder. IR (neat) v = 2267, 1533, 1102, 826 cm-1.1H NMR (400 MHz, CDCl3) δ 7.04 (s, 4H).13C NMR (100 MHz, CDCl3) δ 131.1, 125.9. HRMS (ESI-TOF) m / z: calc’d for C8H5N2O22CH3OH [M + 2CH3OH]+199.0965, found 199.0964.

[0052] Compound 11 - 1,4-toluene diisocyanate:Compound 11 was synthesized according to the above procedure using 9 (1.85 g, 8.9 mmol, 1.0 equiv.) and concentrated HC1 (1.53 mL, 2.1 equiv.) dissolved in 175 mL DI water. The second solution consisted of NaNO2(1.35 g, 19.6 mmol, 2.2 equiv.) in 175 mL of DI water. A 95:5 toluene / CHCh solvent system was employed. Following purification as described above, 11 (1.29 g, 7.4 mmol, 83%) was isolated as a yellow oil which solidified into a pale-yellow solid upon storage in the freezer. Physical state: paleyellow solid (solidifies in fridge / freezer). IR (neat) v = 2249, 1526, 1103, 823 cm’1.1H NMR (400 MHz, CDCl3) δ 7.00 (d, J = 8.4 Hz, 1H), 6.93 (d, J = 2.5 Hz, 1H), 6.91 – 6.85 (m, 1H), 2.30 (s, 3H).13C NMR (100 MHz, CDCl3) δ 134.5, 130.9, 130.0, 126.9, 126.1,124.9, 123.3, 18.4. HRMS (ESI-TOF) m / z: calc’d for C9H7N2O22CH3OH [M + 2CH3OH]+239.1026, found 239.1028.

[0053] Compound 12 - / ^-phenylene diamine:A separate run of the flow system described above for the synthesis of 10 was conducted using 8 (0.5 g, 2.58 mmol, 1.0 equiv.), and concentrated HC1 (0.44 mL, 2.1 equiv.) in 50 mL of DI water. A separate solution of NaNO2(0.39 g, 5.71 mmol, 2.2 equiv.) in 52 mL of DI water was also prepared and the system was run as described above. The output feed from the flow system was directly quenched into a 6 M aqueous solution of HC1 (20 mL) which was then stirred at room temperature for 2 hours. The phases were separated, and the aqueous phase was treated with an aqueous solution of sodium bicarbonate, and then extracted with DCM (25 mL x3), dried over sodium sulfate and concentrated on a rotary evaporator to afford 12 (145 mg, 1.34 mmol, 52%) as an off-white solid which darkens into a reddish solid over time. Spectral data matches that which has been previously reported.

[0049] Physical state: pale red solid. IR (neat) v = 3386, 3302, 3198, 3008, 1633, 1511, 1257, 822 cm’1.1H NMR (400 MHz, CDCl3) δ 6.57 (s, 4H), 3.29 (bs, 4H).13C NMR (100 MHz, CDCl3) δ 138.7, 116.8. HRMS (ESLTOF) m / z: calc’d for C6H9N2 [M + H]+109.0760, found 109.0762.

[0054] Compound 13 - 2,5-diaminotoluene:A separate run of the flow system described above for the synthesis of 11 was conducted using 9 (0.5 g, 2.4 mmol, 1.0 equiv.), and concentrated HC1 (0.41 mL, 2.1 equiv.) in 48 mL of DI water. A separate solution of NaNO2(0.37 g, 5.36 mmol, 2.2 equiv.) in 50 mL of DI water was also prepared and the system was run as described above. The output feed from the flow system was directly quenched into a 6 M aqueous solution of HC1 (20 mL) which was then stirred at room temperature for 2 hours. The phases were separated, and the aqueous phase was treated with an aqueous solution of sodium bicarbonate, and then extracted with DCM (25 mL x3), dried over sodium sulfate and concentrated on a rotary evaporator to afford 13 (155 mg, 1.10 mmol, 46%) as a yellowish solid which darkens into a reddish-black solid. Spectral data matches that which has been previously reported.

[0050] Physical state: dark red / black solid. IR (neat) v = 3311, 3027, 2921, 1605, 1501, 1239, 818 cm’1.1H NMR (400 MHz, CDCl3) δ 6.53 (d, J = 8.2 Hz, 1H), 6.48 (d, J = 2.6 Hz, 1H), 6.44 (dd, J = 8.1, 2.7 Hz, 1H), 3.14 (s, 4H), 2.11 (s, 3H).13C NMR (100 MHz, CDCl3) δ 138.7, 137.0, 124.3, 118.4, 116.6, 114.4, 17.7. HRMS (ESI-TOF) m / z: calc’d for C7H11N2 [M + H]+123.0917, found 123.0915.

[0055] Compound S2 - 1,4-toluene diisocyanate from non-renewable precursor:2-methyl-l,4-benzenedicarboxylic acid (5.0 g, 27.8 mmol, 1.0 equiv.), H2SO4 (0.3 mmol, 5.6 mmol, 0.2 equiv.), and EtOH (150 mL) were refluxed for 18 hours. The mixture was cooled to room temperature and concentrated. The resultant white sludge was dissolved in EtOAc (100 mL), washed with saturated NaHCCh (50 mL), and then brine, and then concentrated to afford an off-white solid. The crude diester was dissolved in EtOH (75 mL) and hydrazine monohydrate (8 mL, 6.0 equiv.) was added, and the mixture was refluxed for 18 hours. Compound S2a (3.7 g, 17.8 mmol, 64%) was isolated as a white powder in identical fashion as described above for the synthesis of 9. Compound S2 was synthesized using the flow system described above using S2a (2.5 g, 12 mmol, 1.0 equiv.) and concentrated HC1 (2.06 mL, 2.1 equiv.) dissolved in 215 mL DI water. The secondsolution consisted of NaNO2(1.81 g, 26.4 mmol, 2.2 equiv.) in 215 mL of DI water. A 95:5 toluene / CHCh solvent system was employed. Following purification, S2 (1.71 g, 9.8 mmol, 82%) was isolated as a yellow oil which solidified into a pale-yellow solid upon storage in the freezer. Spectral data matched that which was reported above for compound 11.

[0056] Synthesis and Characterization of TPUs. All the precursors required to synthesize the TPU including polyol, chain extender and diisocyanate, were heated at 80 °C before use. The synthetic procedure of AzAPDO polyol has been discussed in detail in our previous work.

[0051] The molecular weight of AzA-PDO polyol (as determined from its hydroxyl number value-79.8) was 1405 g / mol. In a plastic cup, AzA-PDO polyol (4.21g, 0.003 mol), 1,4-butanediol as chain extender (0.27g, 0.003) and 0.04 weight% DBTDL catalyst (1.8pL) were mixed in a Flacktek speed mixer at 2000 rpm for 50 seconds. To this mixture, the aromatic diisocyanate (0.0066 mol, 1.15g) was added followed by mixing the contents for a duration of 30 seconds. The TPUs were cured in these cups at 80 °C for 48 h. The appearance of the peak around 7-7.2 ppm in the1H NMR (as shown below) can be assigned to the -NH proton, implying the successful formation of urethane linkage in TPUs. The properties of illustrative TPUs are shown in Table 1.Synthesis of TPU1:Synthesis ofTPU2 / TPU3:wwrrn

[0057] Table 1: Summary of properties of TPUs.

[0058] Optimization of the Electrochemical Decarboxylative Aromatization

[0059] Table 2:, Base...... Current, Yield (%)aEntry Solvent,., Electrolyte,.. F / mol — - -s~ —J(equiv.)J(mA) 6 71 ACN - ”BU4NOAC20 8 7 9(1.5 eq.)”BU4N0ACDCM 20 8 trace trace (1-5 eq.)”BU4NOAC3 Acetone 20 8 n.d. n.d.(1.5 eq.)2,6-lutidine ”Bu4NPFe (0.14 ACN 20 8 14 112,6-lutidine ”Bu4NPFe (0.15 DCM 20 8 6 82,4,6- U4NPF6(0.16 ACN 20 8 21 20 collidine2,4,6- U4NPF6(0.17 DCM 20 8 28 30 collidine2,4,6- U4NPF6(0.18 Acetone 20 8 15 18 collidine2,4,6- BruNBr (0.19 DCM 20 8 n.d. n.d.collidine2,4,6- U4NI (0.110 DCM 20 8 n.d. n.d.collidine2,4,6- 'BiuNClCM11 DCM 20 8 31 26 collidine(0.1 M)2,4,6- 'BiuNClCM12 ACN 20 8 21 19 collidine(0.1 M)2,4,6- "BU4NCIO413 Acetone 20 8 28 26 collidine(0.1 M)2,4,6- LiCIC (0.114 Acetone 20 8 42 38 collidine2,4,6- LiCIC (0.115 Acetone 20 8 35 39 collidine2,4,6- LiCIC (0.116 ACN 20 8 24 22 collidine2,4,6- LiCIC (0.117 MeOH 20 8 14 20 collidine2,4,6- LiCIC (0.118 DMF 20 8 n.d. n.d.collidine2,4,6- LiCIC (0.119 HFIP 20 8 18 24 collidine2,4,6- LiCIC (0.120 20 8 58 64 DCM / Acetone collidine2,4,6- LiCIC (0.121b1 1 20 8 29 34 _ DCM / acetone collidine22 1: 1 2,4,6- LiCIC (0.120 8 23 25 DCM / acetone collidine2,4,6- LiCIC (0.123c 1 120 8 34 39 DCM / acetone collidine2,4,6- LiCIC (0.124 1 1 30 8 51 55 DCM / acetone collidine2,4,6- LiCIC (0.125 1 1 10 8 37 34 _ DCM / acetone collidine26 1: 1 2,4,6- LiCIC (0.1 20 10 51 53DCM / acetone collidine (2) M)a 1H NMR yieldbreaction was run without argon degassingcsignificant electrode fouling was observed

[0060] General procedure for reaction optimization: To a 20 mL vial was added 5 or 6 (0.5 mmol, 1.0 equiv.), followed by addition of electrolyte, base and 8 mL of solvent. The mixture was stirred at room temperature for 5 minutes until complete dissolution of the reagents. The mixture was then sparged with an argon balloon for 5 minutes and then promptly sealed with a custom cap equipped with two cylindrical graphite electrodes (6 mm diameter, 70 mm in length). The mixture was then electrolyzed under constant current. After a determined amount of charge had been passed through the system, the electrodes were rinsed with acetone, and the solvent was removed. The resulting solid mixture was dissolved in EtOAc (15 mL), washed with 0.5 M HCl (15 mL) and brine (15 mL), and then concentrated. The crude mixture was then analyzed via1H NMR containing an internal standard to calculate yields which are reported in Table 2.

[0061] Cyclic Voltammetry Studies on Substrates 4 and 5 (FIGs. 1A and IB).Cyclic voltammetry (CV) was performed using a Pine WaveDriver 100 potentiostat with a glassy carbon working electrode (3.0 mm diameter), a platinum mesh counter electrode, and a silver wire pseudo-reference electrode (potentials are referenced to Fc+ / 0, measured at E1 / 2(Fc+ / 0) = 0.31 V versus the Ag pseudo-reference electrode). The electrolyte in all experiments was 0.1 M LiCICU in 1: 1 DCM / ACN (ACN was used as a co-solvent instead of acetone due to its superior electrochemical stability and ease of drying), with analytes 4 and 5 at a concentration of 1.5 mM. Cyclic voltammograms were collected at a scan rate of 100 mV / s. The cell was sparged with N2 for 10 min prior to each experiment, and the working electrode was polished between experiments. The cyclic voltammograms show oxidation events for 4 and 5 only in the presence of 2,4,6-collidine, with half peak potentials (Ep / 2) measured at 1.31 V and 1.23 V for substrates 4 and 5, respectively. The observed base dependence and chemically irreversible oxidation waves are consistent with oxidation of a carboxylate anion, and the measured Ep / 2 values match closely with oxidation potentials previously reported for secondary

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[0062] While certain embodiments have been illustrated and described, it should be understood that changes and modifications can be made therein in accordance with ordinary skill in the art without departing from the technology in its broader aspects as defined in the following claims.

[0063] The embodiments, illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising,” “including,” “containing,” etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed technology.Additionally, the phrase “consisting essentially of’ will be understood to include those elements specifically recited and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase “consisting of’ excludes any element not specified.

[0064] The present disclosure is not to be limited in terms of the particular embodiments described in this application. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims areentitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions, or biological systems, which can of course vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0065] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0066] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0067] All publications, patent applications, issued patents, and other documents referred to in this specification are herein incorporated by reference as if each individual publication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by reference in its entirety. Definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure.

[0068] Other embodiments are set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A process for the production of a compound, the process comprising:subjecting a compound of Formula (I) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II);wherein:the compound of Formula (I) is:the compound of Formula (II) is:R1is H or alkyl; andR2is alkyl.

2. The process of claim 1, wherein R1is Ci-Ce alkyl and R2is H or Ci-Ce alkyl.

3. The process of claim 1, wherein the compound of Formula (I) is prepared by contacting an esterified monosaccharide with a deoxydehydration catalyst to form a compound of Formula (III) R1OC(O)C=CH-CH=C(O)COR1; and contacting the compound of Formula (III) with a compound of Formula (IV) H2C=C(CC>2H)(R2) in the presence of a radical scavenger to form the compound of Formula (I).

4. The process of claim 3, wherein R1is methyl or ethyl and R2is H, methyl or ethyl.

5. The process of claim 3, wherein the radical scavenger is hydroquinone.

6. The process of claim 1, wherein the salt is an alkyl ammonium salt or a perchlorate salt.

7. The process of claim 6, wherein the salt is tetrabutyl ammonium acetate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, tetrabutylammonium perchlorate, lithium perchlorate, sodium perchlorate, or potassium perchlorate.

8. The process of claim 1, wherein a base is present in the electrochemical decarboxylation aromatization reaction.

9. The process of claim 8, wherein the base is a hindered pyridine.

10. The process of claim 9, wherein the hindered pyridine is 2,6-lutidine or 2,4,6- collidine.

11. The process of claim 1, wherein the electrochemical decarboxylative aromatization reaction is conducted in the presence of graphite electrodes.

12. A process for the production of a diisocyanate of Formula (VI), the process comprising:subjecting a compound of Formula (I) to an electrochemical decarboxylative aromatization reaction in the presence of a salt to form a compound of Formula (II);contacting the compound of Formula (II) with an azide forming reagent to form a compound of Formula (V); andheating the compound of Formula (V) to produce a compound of Formula (VI); wherein:the compound of Formula (I) is:the compound of Formula (II) is:the compound of Formula (VI) is:R1is alkyl; andR2is H or alkyl.

13. The process of claim 12, wherein the electrochemical decarboxylative aromatization reaction is conducted in the presence of graphite electrodes.

14. A process for the production of a diolefinic diester, the process comprising contacting an esterified monosaccharide of Formula (VII):with triethylorthoformate in the presence of p-toluenesulfonic acid followed by treatment with acetic anhydride to form a di olefin diester of Formula (III) R1OC(O)C=CH-CH=C(O)COR1, wherein R1is alkyl.

15. The process of claim 14, wherein the compound of Formula (VII) is trans, trans- muconic acid.

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