Jojoba oil olefin metathesis: a valuable source for bio-renewable materials

Winkler M., Meier M.A.

Olefin cross-metathesis of unsaturated fatty acid methyl ester (FAME) derived benzyl carbamates with methyl acrylate is described. The obtained by-product, an α,β-unsaturated ester, was further modified via thia-Michael addition reactions in order to synthesize branched AA-type or AB-type monomers for the preparation of polyesters, which are tuneable by oxidation. Cross-metathesis of fatty acid derived carbamates was used as a novel approach to prepare linear AB-type monomers, which can be used for the preparation of renewable polyamides PA11, PA12 and PA15. The necessary fatty acid carbamates were prepared by applying a catalytic Lossen rearrangement procedure. The presented synthesis strategy has potential for the bio-sourced preparation of monomers for the production of polyamides. All prepared polymers were fully characterized by NMR, SEC, and DSC analyses. Additionally, the Young's modulus of the prepared long-chain polyamide PA15 was determined.

Sehlinger A., Stalling T., Martens J., Meier M.A.

Novel structural motifs in macromolecular chemistry are introduced by the use of the Asinger multicomponent reaction. The combination of ammonia, acetone, α-chloroisobutyraldehyde, and either water or sodium hydrosulfide, leads to an oxazoline or thiazoline scaffold, respectively, which is subsequently modified with 10-undecenol and 10-undecenoyl chloride to obtain heterocycle-functionalized α,ω-dienes. These substrates are used as monomers in an acylic diene metathesis (ADMET) or thiol-ene step-growth polymerization. The thus-obtained polymers are studied in post-polymerization modifications, like hydrogenation and oxidation. Here, the thiazolidine- and oxazolidine-containing polymers show dramatically different chemical stability due to the heterocyclic moieties.

Simocko C., Wagener K.B.

Boron-containing Lewis acids have shown a profound effect on the cross-metathesis reaction of 1-hexene. Grubbs first-generation catalyst shows over 100% improvement in conversion in some cases, while the yields increase by up to 50% with Grubbs second-generation catalyst. With the inclusion of boron-containing Lewis acids, compounds prepared using Grubbs second-generation-type catalysts display significantly reduced levels of isomerization.

Nuyken O., Pask S.

Dupé A., Le Ravalec V., Fischmeister C., Bruneau C.

Two synthetic approaches to produce functionalized plant oil derivatives were investigated. The ruthenium-catalyzed ene-yne cross-metathesis of propargylic carbonates with terminal olefins arising from ethenolysis of methyl oleate provides conjugated dienes. It was shown that the reactivity of these dienes in Diels–Alder [4 + 2]-cycloaddition with symmetrical electron-deficient alkynes towards the formation of cyclohexadienes was effective but limited by stereochemical considerations. On the other hand, the stepwise ene-yne cross-metathesis followed by ruthenium-catalyzed nucleophilic allylic substitution by O, N, and C-nucleophiles was very efficient both in term of reactivity and regioselectivity.

Firdaus M., Meier M.A.

► Vanillin is studied as renewable monomer precursor. ► High molecular weight copolymers were obtained by three different routes. ► These polyesters are fully characterized. Renewable monomers derived from vanillin and fatty acids have been studied as monomers in ADMET, thiol-ene addition, and polycondensation type polymerization reactions. Both synthesized monomers and polymers were adequately characterized by NMR, DSC, and GPC. The synthesis of polymers via ADMET was optimized with regard to the applied catalyst and catalyst loading. Remarkably, it turned out that ADMET polymerizations led to high molecular weights (up to 50 kDa), whereas thiol-ene polyaddition and polycondensation led to polymers with molecular weight up to 15 and 17 kDa, respectively. Thermoplastic materials with melting points in the range from 15.8 to 77.8 °C and T g s in the range from −37.0 to −13.6 °C were thus obtained.

Lummiss J.A., Oliveira K.C., Pranckevicius A.M., Santos A.G., dos Santos E.N., Fogg D.E.

As society faces a future of dwindling petrochemical supplies at increasing cost, much attention has been focused on methods to degrade biomass into renewable commodity-chemical building blocks. Reported here is a powerful complementary approach that amplifies the complexity of molecular structures present in plant materials. Essential-oil phenylpropenoids are transformed via acrylate cross-metathesis into potent antioxidants that are widely used in perfumery and cosmetics, and in treating disorders associated with oxidative damage.

Faruk O., Bledzki A.K., Fink H., Sain M.

Due to environment and sustainability issues, this century has witnessed remarkable achievements in green technology in the field of materials science through the development of biocomposites. The development of high-performance materials made from natural resources is increasing worldwide. The greatest challenge in working with natural fiber reinforced plastic composites is their large variation in properties and characteristics. A biocomposite's properties are influenced by a number of variables, including the fiber type, environmental conditions (where the plant fibers are sourced), processing methods, and any modification of the fiber. It is also known that recently there has been a surge of interest in the industrial applications of composites containing biofibers reinforced with biopolymers. Biopolymers have seen a tremendous increase in use as a matrix for biofiber reinforced composites. A comprehensive review of literature (from 2000 to 2010) on the mostly readily utilized natural fibers and biopolymers is presented in this paper. The overall characteristics of reinforcing fibers used in biocomposites, including source, type, structure, composition, as well as mechanical properties, will be reviewed. Moreover, the modification methods; physical (corona and plasma treatment) and chemical (silane, alkaline, acetylation, maleated coupling, and enzyme treatment) will be discussed. The most popular matrices in biofiber reinforced composites based on petrochemical and renewable resources will also be addressed. The wide variety of biocomposite processing techniques as well as the factors (moisture content, fiber type and content, coupling agents and their influence on composites properties) affecting these processes will be discussed. Prior to the processing of biocomposites, semi-finished product manufacturing is also vital, which will be illustrated. Processing technologies for biofiber reinforced composites will be discussed based on thermoplastic matrices (compression molding, extrusion, injection molding, LFT-D-method, and thermoforming), and thermosets (resin transfer molding, sheet molding compound). Other implemented processes, i.e., thermoset compression molding and pultrusion and their influence on mechanical performance (tensile, flexural and impact properties) will also be evaluated. Finally, the review will conclude with recent developments and future trends of biocomposites as well as key issues that need to be addressed and resolved.

Ohlmann D.M., Tschauder N., Stockis J., Gooßen K., Dierker M., Gooßen L.J.

The dimeric palladium(I) complex [Pd(μ-Br)(t)Bu(3)P](2) was found to possess unique activity for the catalytic double-bond migration within unsaturated compounds. This isomerization catalyst is fully compatible with state-of-the-art olefin metathesis catalysts. In the presence of bifunctional catalyst systems consisting of [Pd(μ-Br)(t)Bu(3)P](2) and NHC-indylidene ruthenium complexes, unsaturated compounds are continuously converted into equilibrium mixtures of double-bond isomers, which concurrently undergo catalytic olefin metathesis. Using such highly active catalyst systems, the isomerizing olefin metathesis becomes an efficient way to access defined distributions of unsaturated compounds from olefinic substrates. Computational models were designed to predict the outcome of such reactions. The synthetic utility of isomerizing metatheses is demonstrated by various new applications. Thus, the isomerizing self-metathesis of oleic and other fatty acids and esters provides olefins along with unsaturated mono- and dicarboxylates in distributions with adjustable widths. The cross-metathesis of two olefins with different chain lengths leads to regular distributions with a mean chain length that depends on the chain length of both starting materials and their ratio. The cross-metathesis of oleic acid with ethylene serves to access olefin blends with mean chain lengths below 18 carbons, while its analogous reaction with hex-3-enedioic acid gives unsaturated dicarboxylic acids with adjustable mean chain lengths as major products. Overall, the concept of isomerizing metatheses promises to open up new synthetic opportunities for the incorporation of oleochemicals as renewable feedstocks into the chemical value chain.

Bilel H., Hamdi N., Zagrouba F., Fischmeister C., Bruneau C.

The ruthenium-catalyzed cross-metathesis of eugenol derivatives with electron deficient olefins is reported. It is shown that in the presence of ruthenium catalysts, eugenol and its O-protected derivatives have a high tendency to undergo carbon–carbon double bond migration before and after metathesis leading to the formation of conjugated styrene derivatives. The addition of 1,4-benzoquinone suppresses these isomerization reactions and provides an efficient access to new polyfunctional phenol derivatives upon cross-metathesis of the biosourced eugenol with acrylates, acrylonitrile and acrylamides.

Miao X., Fischmeister C., Dixneuf P.H., Bruneau C., Dubois J.-., Couturier J.-.

The ruthenium-catalyzed cross-metathesis of the unsaturated fatty acid derivative 10-undecenenitrile 1 arising from castor oil with methyl acrylate produces a C12 nitrile ester with high turnover number. This product has potential as a new bio-sourced intermediate for the production of polyamides. This route competes favourably with the reverse cross-metathesis of methyl 10-undecenoate with acrylonitrile leading to the same C12 α,ω-amino ester 7 after hydrogenation of the carbon–carbon double bond and the nitrile functionality.

Chikkali S., Mecking S.

The range of applications for plant oils in the chemical industry could be expanded by modern catalytic processes. The industrial application of olefin metathesis requires high catalyst activities, which influences the choice of the reaction. The mixture of fatty acids in a technical-grade plant oil substrate gives rise to a range of products. This determines the possible process schemes. Potentially novel chemicals and intermediates can be formed.

Kreye O., Türünç O., Sehlinger A., Rackwitz J., Meier M.A.

The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiol-ene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiol-ene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light.

Mutlu H., Parvulescu A.N., Bruijnincx P.C., Weckhuysen B.M., Meier M.A.

The potential of butadiene ditelomers for the synthesis of polymers has been investigated for the first time following two different approaches: acyclic diene metathesis (ADMET) polymerization and thiol–ene polyaddition. The feasibility of both step-growth polymerization methods has been investigated by focusing on the particular polymerization behavior of these unusual monomers. It has been shown that ring-closing metathesis of the studied ditelomers predominates in the first steps of ADMET, followed by oligomerization and double bond isomerization. On the other hand, during thiol–ene polyaddition, additional isomerization reactions, converting allyl ether moieties to vinyl ether moieties, were observed. Generally, the thiol–ene polymerization approach led to higher molecular weight polymers with better characteristics and interesting material properties.

Vennestrøm P.N., Osmundsen C.M., Christensen C.H., Taarning E.

The use of renewable resources has attracted significant attention in recent years for many different reasons. 2] Renewable resources include electricity made from kinetic energy stored in wind, potential energy stored in water, thermal energy stored as heat underground and as solar influx in the form of electromagnetic radiation, and energy stored in chemical bonds in the case of biomass. Although renewable resources have been used for various purposes for centuries, there is currently a significant focus on expanding and optimizing this use in the form of new technologies fit for the 21st century. The use of biomass as a resource has developed rapidly in recent years, and it will become an important contributor to our available resources in the future. Biomass sets itself aside from the other renewable resources, since the energy it contains is stored as chemical bonds. This characteristic allows biomass to be used for several purposes apart from electricity and heat generation, such as the production of liquid fuels and chemicals. Indeed, biomass is the only renewable source of useful carbon atoms. Although biomass is annually renewable, it is still a scarce and limited resource, especially when produced in a sustainable manner, and it is important to use it in the most efficient way. This Essay argues for the production of select chemicals, thereby effectively replacing petroleum, as an efficient use and illustrates some of the current efforts that are made in the chemical industry towards adoption of biomass as a feedstock. Availability of Biomass Resources

Antonova Alexandra S., Zubkov Fedor I.

Catalytic olefin metathesis using Hoveyda-Grubbs type ruthenium complexes is a powerful tool for creating complex molecules possessing a variety of practically useful properties. This method is also applied for obtaining modern polymer materials from low-demand petroleum products. Among all ruthenium complexes containing five- or six-membered chelate rings, the commercially available HG-II catalyst is the most common. In addition, other Hoveyda-Grubbs type complexes, which include a Het→Ru donor–acceptor bond in the chelate ring, often exhibit metathesis activity equal to or superior to that of HG-II. This review considers second-generation N-heterocyclic ruthenium carbene Hoveyda-Grubbs type complexes with donor–acceptor bonds such as O→Ru, S→Ru, Se→Ru, N→Ru, P→Ru and Hal→Ru in the chelate ring. Methods of preparation, analysis of stability and catalytic activity of such complexes are compared, and examples of the application of these organometallic ruthenium derivatives in the synthesis of practically relevant products are provided. The literature from 2010 to 2023 is summarized, making this review useful for a broad audience of chemists working in heterocyclic and organometallic chemistry, as well as practitioners involved in the production of catalysts and polymers.The bibliography includes 174 references.

Forrester M.J., Lin F., Cochran E.W.

There are a wide variety of methods for producing polymers derived from biological sources. As will be discussed in other chapters 8 and 9, it is possible to use natural polymers such as polysaccharides and proteins to produce biobased plastics directly. However, it is also possible to convert many types of biomass into monomers for polymerization into novel biopolymers. These materials may have unique properties that can make them preferred over their petrochemical analogues and as such are often referred to as “bioadvantaged polymers”. This chapter will review a select number of polymerization methods, their governing mechanisms, and basic theory for producing biobased plastics. In detail, step-growth polymerization, ionic polymerization, metathesis polymerization, and radical polymerization will be reviewed. In addition, some of the common challenges associated with these polymerization methods that arise from feedstocks that have a high degree of functionality, typical for biobased materials (plants based oils, proteins, and polysaccharides), will also be reviewed. These challenges can lead to low molecular weight polymers and/or broad molecular weight distributions. Thus, this chapter will review possible solutions to the challenges posed by the various polymerization methods.

Musso J.V., Gebel P., Gramm V., Frey W., Buchmeiser M.R.

Lemcoff N., Nechmad N.B., Eivgi O., Yehezkel E., Shelonchik O., Phatake R.S., Yesodi D., Vaisman A., Biswas A., Lemcoff N.G., Weizmann Y.

Light-induced catalysis and thermoplasmonics are promising fields creating many opportunities for innovative research. Recent advances in light-induced olefin metathesis have led to new applications in polymer and material science, but further improvements to reaction scope and efficiency are desired. Herein, we present the activation of latent ruthenium-based olefin metathesis catalysts via the photothermal response of plasmonic gold nanobipyramids. Simple synthetic control over gold nanobipyramid size results in tunable localized surface plasmon resonance bands enabling catalyst initiation with low-energy visible and infrared light. This approach was applied to the ROMP of dicyclopentadiene, affording plasmonic polymer composites with exceptional photoresponsive and mechanical properties. Moreover, this method of catalyst activation was proven to be remarkably more efficient than activation through conventional heating in all the metathesis processes tested. This study paves the way for providing a wide range of photoinduced olefin metathesis processes in particular and photoinduced latent organic reactions in general by direct photothermal activation of thermally latent catalysts. Current strategies for photoinduced olefin metathesis lack wavelength tunability. Now, plasmonic nanoparticles have been used to activate latent ruthenium catalysts, enabling light-induced olefin metathesis in the infrared range with several advantages when compared with conventional heating. Implementing this approach in ring-opening metathesis polymerization resulted in photoresponsive polymer–nanoparticle composites with enhanced mechanical properties.

Zhao L., Zeng X.

Summary Cyclic (alkyl or aryl)aminocarbenes (CAACs/CArACs) have been prepared by replacement of one of the amino substituents of normal (diamino)carbenes (NHCs) by alkyl or aryl scaffolds, showing stronger nucleophilicity and electrophilicity than commonly used phosphine and NHC ligands. As a result, their use in tuning the electronic properties and steric environments of coordinated metals in catalytic reactions is of great interest. Significant progress in the field has been made, showing the interesting ability of CAACs/CArACs as ligands in promoting organic reactions. A broad range of catalytic reactions, including hydroamination, hydrogenation, olefin metathesis, borylation, and other transformations, have been developed with CAAC/CArAC ligands addressing the synthetic challenges associated with molecular construction. This review demonstrates the development of organic reactions with CAAC/CArAC ligands from the view of synthetic chemistry, focusing on the discussion and elucidation of related mechanisms for insight into the discovery of new reactions.

Liu S., Yan J., Zhang Q., Yan Y.

Since the discovery of acyclic diene metathesis (ADMET), researchers have gradually developed ADMET polymerization into a mature methodology for the preparation of versatile polymers with various precise functional groups. As a representative stepwise polymerization method, ADMET enable the polymerization of relatively “inert” acyclic diene monomers. By rational design of monomer structures, the resulted functional materials can be used in various fields such as biomedicine, optoelectronics and stimulus responsive materials. This review will focus on the synthetic strategies of functional polymers with various precise moieties by ADMET over the past few decades, especially functional polyesters, polyethers, polyolefins, and conjugated polymers as well as organometallic polymers will be summarized. Acyclic diene metathesis not only provides facile method for the polymerization of relatively “inert” acyclic diene monomers, but also gives polymers with versatile architectures and functionalities that cannot prepared via conventional polymerization methods. This comprehensive review summarizes the rational design of monomers for ADMET polymerization and corresponding synthesis of functional polyesters, polyethers, polyolefins, and conjugated polymers as well as organometallic polymers.

Dewez D.F., Diacofotaki C., Evano G.

An entry to new classes of nitrogen-containing heterocycles featuring both a cyanamide and an unsaturated 5-, 6- or 7-membered ring is reported by RCM of the corresponding N-alkenyl-cyanamides, new partners for olefin metathesis.

Phatake R.S., Vidavsky Y., Lemcoff N.G., Reany O.

The influences of oil additives on thermomechanical properties of polymers made by ROMP of DCPD-OH are explored. A noticeable correlation between the gradual increase of T g values and the rise of cross-linking densities vs . oil content in the polymeric films was observed. A fine interplay between cross-linking and plasticizing effects determines the film's mechanical properties. • DCPD-OH, oil additives and G-II catalyst afforded tunable ROMP cross-linked polymers. • All polymeric blends display higher T g ’s than that of the parent poly-DCPD-OH. • Polymeric blends gained strength, as well as reduced plastic strain compared to poly-DCPD-OH. • Cross-linking and plasticizing effects determined the film's mechanical properties. • Several oils can improve the thermal and mechanical properties of DCPD-based polymers. Ring opening metathesis polymerization (ROMP) derived poly-dicyclopentadiene (poly-DCPD) materials enjoy high impact strength, and high chemical resistance. They offer control over the thermomechanical properties of the resulting cross-linked polymers, depending on initiator type and loading, the curing method and the monomer's chemical structure. Herein, we report on an additional method to tune properties of novel thermoset polymers obtained by ROMP by using blended mixtures containing 1-hydroxy-dicyclopentadiene ( DCPD-OH ) and four different oil additives, silicone oil ( SO ), mineral oil ( MO ), jojoba oil ( JO ) and linseed oil ( LO ). Various parameters such as curing behavior, glass transition temperatures ( T g ), cross-link densities and mechanical properties were studied. Accordingly, all the polymeric blends are amorphous, display higher T g than that of the parent poly-DCPD-OH and retained their thermal stability. T g values increased with a rise in the oil content until phase segregation in the polymeric films was dominant. This trend was also manifested by a gradual increase in the calculated cross-linking density values. Tensile analysis of polymeric blends with the highest cross-linking density values revealed that, although the films gained strength, they also showed reduced plastic strain compared to the parent poly-DCPD-OH. This behavior is explained by the divergent interplay between the plasticizing effects and the cross-linking density in thermoset composites.

Morvan J., Mauduit M., Bertrand G., Jazzar R.

Discovered in 2005, cyclic (alkyl)(amino)carbenes (CAACs) have led to numerous discoveries in the field of ruthenium olefin metathesis, until then largely dominated by the well-known N-heterocyclic...

Behr A., Seidensticker T.

Chapter Timetable

Eivgi O., Phatake R.S., Nechmad N.B., Lemcoff N.G.

The most important means for tuning and improving a catalyst's properties is the delicate exchange of the ligand shell around the central metal atom. Perhaps for no other organometallic-catalyzed reaction is this statement more valid than for ruthenium-based olefin metathesis. Indeed, even the simple exchange of an oxygen atom for a sulfur atom in a chelated ruthenium benzylidene about a decade ago resulted in the development of extremely stable, photoactive catalysts. This Account presents our perspective on the development of dormant olefin metathesis catalysts that can be activated by external stimuli and, more specifically, the use of light as an attractive inducing agent.The insight gained from a deeper understanding of the properties of cis-dichlororuthenium benzylidenes opened the doorway for the systematic development of new and efficient light-activated olefin metathesis catalysts and catalytic chromatic-orthogonal synthetic schemes. Following this, ways to disrupt the ligand-to-metal bond to accelerate the isomerization process that produced the active precatalyst were actively pursued. Thus, we summarize herein the original thermal activation experiments and how they brought about the discoveries of photoactivation in the sulfur-chelated benzylidene family of catalysts. The specific wavelengths of light that were used to dissociate the sulfur-ruthenium bond allowed us to develop noncommutative catalytic chromatic-orthogonal processes and to combine other photochemical reactions with photoinduced olefin metathesis, including using external light-absorbing molecules as sunscreens to achieve novel selectivities. Alteration of the ligand sphere, including modifications of the N-heterocyclic carbene (NHC) ligand and the introduction of cyclic alkyl amino carbene (CAAC) ligands, produced more efficient light-induced activity and special chemical selectivity. The use of electron-rich sulfoxides and, more prominently, phosphites as the agents that induce latency widened the spectrum of light-induced olefin metathesis reactions even further by expanding the colors of light that may now be used to activate the catalysts, which can be used in applications such as stereolithography and 3D printing of tough metathesis-derived polymers.

Tiso T., Sauer D.F., Beckerle K., Blesken C.C., Okuda J., Blank L.M.

Here we report a chemoenzymatic approach to synthesize 1-octene from carbohydrates via ethenolysis of rhamnolipids. Rhamnolipids synthesized by P. putida contain a double bond between carbon five and six, which is experimentally confirmed via olefin cross metathesis. Utilizing these lipids in the ethenolysis catalyzed by a Grubbs−Hoveyda-type catalyst selectively generates 1-octene and with good conversions. This study shows the potential of chemoenzymatic approaches to produce compounds for the chemical industry from renewable resources.

Wang H., Yao Z., Li Z., Zhu Y., Zhang C., Luo Z., Guo T., Gao Y., Zhang L., Guo K.

Polyesters produced by ring-opening polymerization (ROP) of cyclic monomers using organocatalysts were well developed in academia. Industrially viable ROPs were polymerizations at elevated temperatures in the bulk, thus desirable features of useful organocatalysts would be thermal stable, reasonably active in fast polymerization but mild enough to avoid transesterification. More importantly, the polyesters containing residue organocatalyst should met biosafety regulations. In these regards, series of pyridinium halides readily prepared by one step from mass-produced pyridines and hydrohalic acids were evaluated in ROPs of l -lactide (LLA), trimethylene carbonate (TMC), δ-valerolactone, and e-caprolactone in the bulk. An optimal catalyst 4-(N,N-dimethylamino)pyridine hydrochloride (DMAP·HCl) was examined in the catalytic performances in ROPs of LLA, TMC, and diblock copolymerization affording PTMC-b-PLLA. Bulk ROP of LLA at 140 °C produced PLLAs by near quantitative conversions with precise molecular weights (Mn,NMR = 3.3–16.6 kg mol−1) and narrow dispersities (Đ = 1.13–1.17). Kinetics data, chain extension experiments, and MALDI-ToF MS analysis all supported the controlled/living nature of the ROPs. A bifunctional activation mechanism in which pyridinium activated the monomer and halide activated the initiator/chain end was proposed and validated by 1H NMR and 13C NMR titrations. Poly (l -lactide) samples prepared by bulk ROPs of LLA that containing residue catalyst DMAP·HCl were tested by MTT assay in L929 mouse fibroblasts in vitro. High level of relative growth rate (RGR 93.6–96.8%) revealed favorable biosafety of the sample PLLAs.

Peñaranda Gómez A., Rodríguez Bejarano O., Kouznetsov V.V., Ochoa-Puentes C.

In this contribution, a sustainable one-pot diastereoselective synthesis of tetrahydroquinolines through the aza Diels–Alder reaction is reported starting from star anise oil, substituted anilines,...

John G., Nagarajan S., Vemula P.K., Silverman J.R., Pillai C.K.

Owing to the natural abundance, variety of structural features, and highly specific functions, natural monomers render themselves as potential candidates for production of high performance functional polymers. The emerging concept of the biorefinery and development of new biosynthetic routes to synthesize a versatile and broad spectrum of natural monomers and polymers continues to gain momentum. The production of high quality polymers from renewable feedstocks requires innovative chemical modifications and catalytic transformations to achieve higher yields in an efficient manner. A fresh look into monomers available from natural resources such as terpenes, rosin, glycerol, furans, tannins, suberin, their derivatives and miscellaneous monomers may inspire future applications with impactful biobased materials. There are also many areas that require urgent discussion and review pertaining to recent developments in the field; this includes monomer sources that give molecules having special structural features. In particular, cardanol, a naturally occurring low-molecular-weight compound is unique as it contains a phenolic head group and a hydrocarbon chain with different degrees of unsaturation. This molecule possesses functional groups that are amenable for classical chemical modification, which is instrumental in developing a wide range of functional monomers and polymers. A large number of soft and hard materials have been developed from cardanol-based monomers. During the past, a large number of industrial grade materials have been developed from plant-based monomers, including development from microbial and fermentation processes (i.e. lactic acid). This review provides a comprehensive study and survey on recent developments on monomers and polymers derived from urushiol and cardanol based monomers and polymers, vegetable oil-based monomers and polymers, microbially produced monomers and polymers. These all represent emerging fronts giving a vast scope while highlighting important potential material and reagent opportunities.