1,720,995 research outputs found
Synthetic applications of polar organometallic and alkali-metal reagents under air and moisture
Full text linkRecently, there has been an upsurge interest in developing chemoselective and fast processes when working with polar organometallic of s-block and d-block elements and alkali-metal reagents under air and moisture, and also in protic bio-based solvents like Deep Eutectic Solvents or water. A discussion is offered to highlight cutting-edge stoichiometric and catalytic synthetic applications in this evolving field, with an accent over the literature published in the last couple of years
Deep eutectic solvents and their applications as green solvents
Full text linkSeveral examples illustrate the effectiveness of using Deep Eutectic Solvents (DESs) as environmentally responsible reaction media in polar organometallic chemistry, and in metal- and bio-catalysed processes in place of conventional, often hazardous volatile organic compounds (VOCs). Aside from the standpoint of “greenness”, applications of DESs in the above fields also reveal novel aspects of reactivity of practical significance, which are worthy of an in-depth mechanistic understanding: (a) metal-mediated organic transformations can be run in DESs competitively with protonolysis, often at room temperature and under air; (b) metal-catalysed reactions proceed efficiently and under milder conditions in DESs than in VOCs, with the catalyst and DES being easily and successfully recycled; (c) biocatalysts often exhibit higher stability, selectivity and performances in DES mixtures than in aqueous solutions, and a somewhat intriguing stereoselectivit
Reshaping Ullmann Amine Synthesis in Deep Eutectic Solvents: A Mild Approach for Cu-Catalyzed C–N Coupling Reactions With No Additional Ligands
Full text linkThe CuI-catalyzed Ullmann amine cross-coupling between (hetero)aryl halides (Br, I) and
aromatic and aliphatic amines has been accomplished in deep eutectic solvents as
environmentally benign and recycling reaction media. Under optimized conditions, the
reaction proceeds smoothly under mild conditions (60–100◦C) in air, in the absence
of ligands, with a catalyst (CuI) loading of 10 mol% and K2CO3 (aliphatic primary and
secondary amines) or t-BuOK (aromatic amines) as the base. A variety of amines have
been synthesized in yields up to 98% with a broad substrate scope
Exploiting the lithiation-directing ability of oxetane for the regioselective preparation of functionalized 2-aryloxetane scaffolds under mild conditions
No full textElectroactivity of weak electricigen Bacillus subtilis biofilms in solution containing deep eutectic solvent components
Full text linkBacillus subtilis is a Gram-positive, spore-forming bacterium with a versatile and adaptable metabolism, which makes it a viable cell factory for microbial production. Electroactivity has recently been identified as a cellular characteristic linked with the metabolic activity of B. subtilis. The enhancement of B. subtilis electroactivity can positively enhance bioproduction of high-added value metabolites under electrofermentative conditions. Here, we explored the use of deep eutectic solvents (DESs) and DES components as biocompatible nutrient additives for enhancing electroactivity of B. subtilis. The strongest electroactivity was obtained in an aqueous choline chloride: glycerol (1:2 mol mol-1) eutectic mixture. At low concentration (50-500 mM), this mixture induced a pseudodiauxic increase in planktonic growth and increased biofilm formation, likely due to a nutritional and osmoprotectant effect. Similarities in electroactivity enhancements of choline chloride-based eutectic mixtures and quinone redox metabolism in B. subtilis were detected using high performance liquid chromatography and differential pulse voltammetry. Results show that choline chloride-based aqueous eutectic mixtures can enhance biomass and productivity in biofilm-based electrofermentation. However, the specific mechanism needs to be fully elucidated
An enhanced stereoselective synthesis of α,β-unsaturated esters through the Horner–Wadsworth–Emmons reaction in deep eutectic solvents
Full text linkA new scalable synthesis of (E)-alpha,beta-unsaturated esters has been developed using protic, non-toxic, and biodegradable deep eutectic solvents through the Horner-Wadsworth-Emmons reaction between triethyl phosphonates and (hetero)aromatic carbonyl compounds, encompassing electron-withdrawing and electron-donating groups. Stereoselective preparation of disubstituted or trisubstituted ethyl cinnamate derivatives is achieved in the presence of LiOH, K2CO3, or DBU as bases, at room temperature and under air. Demonstrated with the synthesis of (E)-ethyl 3-(4-bromophenyl)acrylate, the same eutectic mixture (choline chloride/urea) proved to be reusable for three consecutive runs. Gram-scale reactions (10 mmol) can be carried out without the formation of side products, thereby ensuring high atom economy and an EcoScale score of 71.An enhanced stereoselective synthesis of alpha,beta-unsaturated esters has been developed using protic and biodegradable deep eutectic solvents
Switchable Deep Eutectic Solvents for Sustainable Sulfonamide Synthesis
Full text linkA sustainable and scalable protocol for synthesizing variously functionalized sulfonamides, from amines and sulfonyl chlorides, has been developed using environmentally responsible and reusable choline chloride (ChCl)-based deep eutectic solvents (DESs). In ChCl/glycerol (1:2 mol mol-1) and ChCl/urea (1:2 mol mol-1), these reactions yield up to 97% under aerobic conditions at ambient temperature within 2-12 h. The practicality of the method is exemplified by the sustainable synthesis of an FFA4 agonist and a key building block en route to anti-Alzheimer drug BMS-299897. A subtle interplay of electronic effects and the solubility characteristics of the starting materials in the aforementioned DESs seem to be responsible for driving the reaction successfully over the hydrolysis of sulfonyl chlorides. The procedure's eco-friendliness is validated by quantitative metrics like the E-factor and the EcoScale, with products isolated by extraction or filtration after decantation
Iron‐Based Deep Eutectic Solvents: Key Players for Amide and Sulfonamide Synthesis and Alcohol Oxidation
No full textA sustainable protocol has been devisedfor the oxidation ofactivated secondary alcohols to theircorresponding carbonyl compounds, as well as their utilization asselective mono-alkylating reagents for both amide and arylsulfonamide derivatives. Thesereactionsproceed smoothly and in good yields (up to 98%) when conducted in Fe-based deep eutectic solvents (DESs), which serve dual roles as solvents and catalysts. Operatingundermild (40 °C) and aerobic conditions,these transformations are completed within a 4 h time frame. A pharmacologically relevant amide derivative, specifically a PMRT1 inhibitor,has also been successfully synthesizedon a 3g-scale utilizinga reusable FeCl3·6H2O/glycerol Lewis acidic DE
Recent Developments in the Lithiation Reactions of Oxygen Heterocycles
No full textThis survey describes how the chemistry of lithiated oxygen heterocycles has been fruitfully exploited, particularly over the last 10 years, for the preparation of more (stereodefined) functionalized derivatives and products derived from them. Also, how they have contributed to natural product synthesis and molecules of relevant pharmaceutical interest. The genesis of the reactive lithiated intermediates (especially alpha- and ortho-lithiated (hetero)arylepoxides, -oxetanes and -tetrahydrofurans) requires a careful choice of the experimental conditions in terms of solvents and temperature in order them to be successfully intercepted by electrophiles. The study of the aggregation and solvation of certain chiral functionalized lithiated oxygen heterocycles has provided further hints about the factors affecting their configurational stability and their carbanionic/carbene-like character, and the way the latter can be finely tuned to facilitate the desired reactivity for synthetic purposes
Dynamic resolution of lithiated ortho-trifluoromethyl styrene oxide and the effect of chiral diamines on the barrier to enantiomerisation
No full textThe first dynamic thermodynamic resolution of a racemic oxiranyllithium is described with selectivities of up to 82 : 18 from a selection of three types of chiral ligands (seven ligands in total). Both (–)-sparteine and its (+)-surrogate were surprisingly found to increase the enantiomerisation barrier
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