Overcoming the limitations of Kolbe coupling with waveform-controlled electrosynthesis

The Kolbe reaction forms carbon-carbon bonds through electrochemical decarboxylative coupling. Despite more than a century of study, the reaction has seen limited applications owing to extremely poor chemoselectivity and reliance on precious metal electrodes. In this work, we present a simple solution to this long-standing challenge: Switching the potential waveform from classical direct current to rapid alternating polarity renders various functional groups compatible and enables the reaction on sustainable carbon-based electrodes (amorphous carbon). This breakthrough enabled access to valuable molecules that range from useful unnatural amino acids to promising polymer building blocks from readily available carboxylic acids, including biomass-derived acids. Preliminary mechanistic studies implicate the role of waveform in modulating the local pH around the electrodes and the crucial role of acetone as an unconventional reaction solvent for Kolbe reaction.

Ozonolysis of α-angelica lactone: a renewable route to malonates

Industrially relevant intermediates such as malonic acid, malonates and 3-oxopropionates can be easily accessed by ozonolysis of α-angelica lactone, derived from the platform chemical levulinic acid. The roles of the solvent and of the quenching conditions are of key importance for the outcome of the reaction.

Comparative analysis of the chemical and biochemical synthesis of keto acids

Keto acids are essential organic acids that are widely applied in pharmaceuticals, cosmetics, food, beverages, and feed additives as well as chemical synthesis. Currently, most keto acids on the market are prepared via chemical synthesis. The biochemical synthesis of keto acids has been discovered with the development of metabolic engineering and applied toward the production of specific keto acids from renewable carbohydrates using different metabolic engineering strategies in microbes. In this review, we provide a systematic summary of the types and applications of keto acids, and then summarize and compare the chemical and biochemical synthesis routes used for the production of typical keto acids, including pyruvic acid, oxaloacetic acid, α-oxobutanoic acid, acetoacetic acid, ketoglutaric acid, levulinic acid, 5-aminolevulinic acid, α-ketoisovaleric acid, α-keto-γ-methylthiobutyric acid, α-ketoisocaproic acid, 2-keto-L-gulonic acid, 2-keto-D-gluconic acid, 5-keto-D-gluconic acid, and phenylpyruvic acid. We also describe the current challenges for the industrial-scale production of keto acids and further strategies used to accelerate the green production of keto acids via biochemical routes.

Highly Efficient Amide Michael Addition and Its Use in the Preparation of Tunable Multicolor Photoluminescent Polymers

The amide bond is one of the most pivotal functional groups in chemistry and biology. It is also the key component of proteins and widely present in synthetic materials. The majority of studies have focused on the formation of the amide group, but its postmodification has scarcely been investigated. Herein, we successfully develop the Michael additions of amide to acrylate, acrylamide, or propiolate in the presence of phosphazene base at room temperature. This amide Michael addition is much more efficient when the secondary amide instead of the primary amide is used under the same conditions. This reaction was applied to postfunctionalize poly(methyl acrylate-co-acrylamide), P(MA-co-Am), and it is shown that the amide groups of P(MA-co-Am) could be completely modified by N,N-dimethylacrylamide (DMA). Interestingly, the resulting copolymer exhibited tailorable fluorescence with emission wavelength ranging from 380 to 613 nm, which is a desired property for luminescent materials. Moreover, the emissions of the copolymer increased with increasing concentration in solution for all excitation wavelengths from 320 to 580 nm. Therefore, this work not only develops an efficient t-BuP₄-catalyzed amide Michael addition but also offers a facile method for tunable multicolor photoluminescent polymers, which is expected to find a wide range of applications in many fields, such as in anticounterfeiting technology.

100th Anniversary of Macromolecular Science Viewpoint: Polymers from Lignocellulosic Biomass. Current Challenges and Future Opportunities

Sustainable polymers from lignocellulosic biomass have the potential to reduce the environmental impact of commercial plastics while also offering significant performance and cost benefits relative to petrochemical-derived macromolecules. However, most currently available biobased polymers are hampered by insufficient thermomechanical properties, low economic feasibility (e.g., high relative cost), and reduced scalability in comparison to petroleum-based incumbents. Future biobased materials must overcome these limitations to be competitive in the marketplace. Additionally, sustainability challenges at the beginning and end of the polymer lifecycle need to be addressed using green chemistry practices and improved end-of-life waste management strategies. This viewpoint provides an overview of recent developments that can mitigate many concerns with present materials and discusses key aspects of next-generation, biobased polymers derived from lignocellulosic biomass.

Properties of Novel Polyesters Made from Renewable 1,4-Pentanediol

Novel polyester polyols were prepared in high yields from biobased 1,4-pentanediol catalyzed by non-toxic phosphoric acid without using a solvent. These oligomers are terminated with hydroxyl groups and have low residual acid content, making them suitable for use in adhesives by polyurethane formation. The thermal behavior of the polyols was studied by differential scanning calorimetry, and tensile testing was performed on the derived polyurethanes. The results were compared with those of polyurethanes obtained with fossil-based 1,4-butanediol polyester polyols. Surprisingly, it was found that a crystalline polyester was obtained when aliphatic long-chain diacids (>C12 ) were used as the diacid building block. The low melting point of the C12 diacid-based material allows the development of biobased shape-memory polymers with very low switching temperatures (<0 °C), an effect that has not yet been reported for a material based on a simple binary polyester. This might find application as thermosensitive adhesives in the packaging of temperature-sensitive goods such as pharmaceuticals. Furthermore, these results indicate that, although 1,4-pentanediol cannot be regarded as a direct substitute for 1,4-butanediol, its novel structure expands the toolbox of the adhesives, coatings, or sealants formulators.

A novel bio-based AB2 monomer for preparing hyperbranched polyamides derived from levulinic acid and furfurylamine

A new AB₂ type bio-based monomer (FDA-E) with two amino functional groups and one ester functional group was prepared from renewable levulinic acid and furfurylamine using a three-step reaction.