Organic electrosynthesis has received great attention as a powerful green tool for synthesis, affording less waste production, less chemicals spent, and often fewer reaction steps than conventional methods. Functional group interconversion and C−C bond generation by imposition of a proper electrode potential is what lies behind organic electrosynthesis processes. Paired electrochemical reactions, indirect electrosynthesis, electrochemical microreactors, and the use of ionic liquids are some of the highlighted means that contribute to optimization of the overall process. Necessity to use specific organic solvents combined with supporting electrolytes is one of the main limitations to be overcome to make the electrochemical process more economically feasible when compared to nonelectrochemical processes. Numerous examples from the bench scale to industrial routes such as adiponitrile, substituted benzaldehydes, anthraquinone, fluorinated products, and succinic acid production are well described throughout this review.
Three 1-ethyl-3-methylimidazolium ([Emim])-based room temperature ionic liquids (RTILs), namely [Emim][Ac] (acetate), [Emim][EtSO4] (ethylsulfate) and [Emim][MeSO3] (methanesulfonate), are tested as additives to alkaline solutions for hydrogen evolution reaction (HER). Electrochemical measurements are performed with a platinum foil working electrode in 8 M KOH solution and after adding 1–2 vol.% of each ionic liquid. Tafel plots are constructed from the polarization curves recorded in different electrolyte compositions and the main HER kinetic parameters are determined. The highest cathodic currents are found upon [Emim][MeSO3] addition. The Volmer reaction is evidenced as the rate determining step by both Tafel analysis and electrochemical impedance spectroscopy (EIS) measurements. EIS data reveal a significant decrease of the overall impedance in the RTILs added solutions. This effect can be due to surface pre-adsorption of the RTIL additives, which stabilize the intermediate hydrogen atoms formed in the Volmer step, thus modifying adsorption and charge transfer processes at the metal-electrolyte interface. This may lead to increased HER currents, as in the case of [Emim][MeSO3] addition. The results support the benefits of using small amounts of selected RTILs as electrolyte additives for the HER in alkaline media.
Multidrug resistance (MDR) in cancer is one of the main limitations for chemotherapy success. Numerous mechanisms are behind the MDR phenomenon wherein the overexpression of the ATP-binding cassette (ABC) transporter proteins P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance protein 1 (MRP1) is highlighted as a prime factor. Natural product-derived compounds are being addressed as promising ABC transporter modulators to tackle MDR. Flavonoids and terpenoids have been extensively explored in this field as mono or dual modulators of these efflux pumps. Nitrogen-bearing moieties on these scaffolds were proved to influence the modulation of ABC transporters efflux function. This review highlights the potential of semisynthetic nitrogen-containing flavonoid and terpenoid derivatives as candidates for the design of effective MDR reversers. A brief introduction concerning the major role of efflux pumps in multidrug resistance, the potential of natural product-derived compounds in MDR reversal, namely natural flavonoid and terpenoids, and the effect of the introduction of nitrogen-containing groups are provided. The main modifications that have been performed during last few years to generate flavonoid and terpenoid derivatives, bearing nitrogen moieties, such as aliphatic, aromatic and heterocycle amine, amide, and related functional groups, as well as their P-gp, MRP1 and BCRP inhibitory activities are reviewed and discussed.
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