Scalable Electrochemical Decarboxylative Olefination Driven by Alternating Polarity.

A mild, scalable (kg) metal-free electrochemical decarboxylation of alkyl carboxylic acids to olefins is disclosed. Numerous applications are presented wherein this transformation can simplify alkene synthesis and provide alternative synthetic access to valuable olefins from simple carboxylic acid feedstocks. This robust method relies on alternating polarity to maintain the quality of the electrode surface and local pH, providing a deeper understanding of the Hofer-Moest process with unprecedented chemoselectivity.

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).

Chemoselective (Hetero)Arene Electroreduction Enabled by Rapid Alternating Polarity.

Conventional chemical and even electrochemical Birch-type reductions suffer from a lack of chemoselectivity due to a reliance on alkali metals or harshly reducing conditions. This study reveals that a simpler avenue is available for such reductions by simply altering the waveform of current delivery, namely rapid alternating polarity (rAP). The developed method solves these issues, proceeding in a protic solvent, and can be easily scaled up without any metal additives or stringently anhydrous conditions.

Interrogation of 2,2'-Bipyrimidines as Low-Potential Two-Electron Electrolytes.

As utilization of renewable energy sources continues to expand, the need for new grid energy storage technologies such as redox flow batteries (RFBs) will be vital. Ultimately, the energy density of a RFB will be dependent on the redox potentials of the respective electrolytes, their solubility, and the number of electrons stored per molecule. With prior literature reports demonstrating the propensity of nitrogen-containing heterocycles to undergo multielectron reduction at low potentials, we focused on the development of a novel electrolyte scaffold based upon a 2,2'-bipyrimidine skeleton.

Homobenzylic Oxygenation Enabled by Dual Organic Photoredox and Cobalt Catalysis.

Activation of aliphatic C(sp)-H bonds in the presence of more activated benzylic C(sp)-H bonds is often a nontrivial, if not impossible task. Herein we show that leveraging the reactivity of benzylic C(sp)-H bonds to achieve reactivity at the homobenzylic position can be accomplished using dual organic photoredox/cobalt catalysis. Through a two-part catalytic system, alkyl arenes undergo dehydrogenation followed by an anti-Markovnikov Wacker-type oxidation to grant benzyl ketone products.

Reversing the Regioselectivity of Halofunctionalization Reactions through Cooperative Photoredox and Copper Catalysis.

Halofunctionalization of alkenes is a classical method for olefin difunctionalization. It gives rise to adducts which are found in many natural products and biologically active molecules, and offers a synthetic handle for further manipulation. Classically, this reaction is performed with an electrophilic halogen source and leads to regioselective formation of the halofunctionalized adducts.

Salicylic acid-based poly(anhydride-ester) nerve guidance conduits: Impact of localized drug release on nerve regeneration.

Nerve guidance conduits (NGCs) can serve as physical scaffolds aligning and supporting regenerating cells while preventing scar tissue formation that often interferes with the regeneration process. Numerous studies have focused on functionalizing NGCs with neurotrophic factors, for example, to support nerve regeneration over longer gaps, but few directly incorporate therapeutic agents. Herein, we fabricated NGCs from a polyanhydride comprised of salicylic acid (SA), a nonsteroidal anti-inflammatory drug, then performed in vitro and in vivo assays.

Hydrodecarboxylation of Carboxylic and Malonic Acid Derivatives via Organic Photoredox Catalysis: Substrate Scope and Mechanistic Insight.

A direct, catalytic hydrodecarboxylation of primary, secondary, and tertiary carboxylic acids is reported. The catalytic system consists of a Fukuzumi acridinium photooxidant with phenyldisulfide acting as a redox-active cocatalyst. Substoichiometric quantities of Hünig's base are used to reveal the carboxylate.

Biodegradable ferulic acid-containing poly(anhydride-ester): degradation products with controlled release and sustained antioxidant activity.

Ferulic acid (FA) is an antioxidant and photoprotective agent used in biomedical and cosmetic formulations to prevent skin cancer and senescence. Although FA exhibits numerous health benefits, physicochemical instability leading to decomposition hinders its efficacy. To minimize inherent decomposition, a FA-containing biodegradable polymer was prepared via solution polymerization to chemically incorporate FA into a poly(anhydride-ester).

Stability of a salicylate-based poly(anhydride-ester) to electron beam and gamma radiation.

The effect of electron beam and gamma radiation on the physicochemical properties of a salicylate-based poly(anhydride-ester) was studied by exposing polymers to 0 (control), 25 and 50 kGy. After radiation exposure, salicylic acid release in vitro was monitored to assess any changes in drug release profiles. Molecular weight, glass transition temperature and decomposition temperature were evaluated for polymer chain scission and/or crosslinking as well as changes in thermal properties.

Salicylic acid-derived poly(anhydride-ester) electrospun fibers designed for regenerating the peripheral nervous system.

Continuous biomaterial advances and the regenerating potential of the adult human peripheral nervous system offer great promise for restoring full function to innervated tissue following traumatic injury via synthetic nerve guidance conduits (NGCs). To most effectively facilitate nerve regeneration, a tissue engineering scaffold within a conduit must be similar to the linear microenvironment of the healthy nerve. To mimic the native nerve structure, aligned poly(lactic-co-glycolic acid)/bioactive polyanhydride fibrous substrates were fabricated through optimized electrospinning parameters with diameters of 600 ± 200 nm.

Microscale plasma-initiated patterning of electrospun polymer scaffolds.

Microscale plasma-initiated patterning (μPIP) is a novel micropatterning technique used to create biomolecular micropatterns on polymer surfaces. The patterning method uses a polydimethylsiloxane (PDMS) stamp to selectively protect regions of an underlying substrate from oxygen plasma treatment resulting in hydrophobic and hydrophilic regions. Preferential adsorption of the biomolecules onto either the plasma-exposed (hydrophilic) or plasma-protected (hydrophobic) regions leads to the biomolecular micropatterns.

Design and evaluation of novel polyanhydride blends as nerve guidance conduits.

Implantable biodegradable nerve guidance conduits (NGCs) have the potential to align and support regenerating cells, as well as prevent scar formation. In this study in vitro bioassays and in vivo material evaluations were performed using a nerve guidance conduit material made from a novel polyanhydride blend. In vitro cytotoxicity studies with both fibroblasts and primary chick neurons demonstrated that the proposed polyanhydride blend was non-cytotoxic.

A novel approach for incorporation of mono-functional bioactive phenols into polyanhydrides.

Antiseptics based on phenol and phenolic derivatives were chemically incorporated into polyanhydrides as pendant groups via ester linkages. Polyanhydrides with antiseptic loadings of 46-58 wt.-% were obtained with molecular weights ranging from 9 400-23 000.

Comparison of salicylate-based poly(anhydride-esters) formed via melt-condensation versus solution polymerization.

Salicylate-based poly(anhydride-esters) were synthesized via two different methods, melt-condensation and solution polymerization, and the resulting polymers were compared. Acetylsalicylic acid was used as a model compound to mimic the active polymer chain-ends during melt-condensation, and formed a low-molecular-weight (<1500) polymer when subjected to melt-condensation polymerization conditions. The polymers and model compounds were analyzed by NMR ((1)H and (13)C) and IR spectroscopies to elucidate the structures.