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A method is described for the NMR-based screening for the discovery of aminoglycoside mimetics that bind to Escherichia coli A-site RNA. Structural models of the A-site RNA/ligand complexes are prepared and compared to the three-dimensional structures of the RNA/aminoglycoside complexes.

A NMR-based method is described for screening proteins containing 13C-labeled methyl groups of leucine, valine and isoleucine.

In this work, solid–liquidequilibria (SLE) data for theternary 3-nitrophthalic anhydride + 4-nitrophthalic anhydride + 1,4-dioxanesystem were obtained at (283.15, 303.15, and 323.15) K. The solid–liquidphase diagrams of the ternary system were constructed based on themeasured solubility data. There existed two pure solid phases at eachtemperature in the studied system, pure 3-nitrophthalic anhydrideand 4-nitrophthalic anhydride, which were identified by the wet residuemethod of Schreinemaker. Furthermore, the density (ρ) of theequilibrium liquid phase was determined. The ternary phase diagramand solubility data for the system 3-nitrophthalic anhydride + 4-nitrophthalicanhydride + 1,4-dioxane, which shows a much more practical applicationfor the region where pure 3-nitrophthalic anhydride and 4-nitrophthalicanhydride are obtained, are much larger than those in the system with2-propanone as a solvent. [ABSTRACT FROM AUTHOR]

A novel intumescent flame retardant-polyacrylamide (IFR-PAM)was prepared by the copolymerization of N1-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-yl)-acrylamide(DPAA) and acrylamide and was used to prepare various IFR-PAM/grapheneoxide (GO) thin films via layer-by-layer (LbL) assembly as a flameretardant coating system for cotton fabric. Films assembled with IFR-PAMand GO nanosheets show linear growth as a function of the number ofbilayer deposited. Higher hydrophobe DPAA content of IFR-PAM resultsin much thicker assemblies due to hydrophobic association. The resultsfrom X-ray diffraction (XRD), atomic force microscopy (AFM), and scanningelectronic microscopy (SEM) indicate that the IFR-PAM/GO ultrathinfilms with high homogeneity and orientation are formed by LbL assemblydriven by hydrogen interaction. The thermogravimetric analysis (TGA)results indicate that the IFR-PAM/GO coating improves the thermalstability of cotton fabric. Cone calorimeter testing shows that theIFR-PAM/GO-coated fabrics become less flammable with lower peak heatrelease rate (PHRR) and longer time to ignition (TTI). SEM imagesdemonstrate that the surface of the IFR-PAM/GO-coated fabrics is coveredby a layer of continuous and compact char after combustion. [ABSTRACT FROM AUTHOR]

The radical 1,3-hydro-di/monofluoromethylation of N,N' -cyclic azomethine imines with HCF 2 SO 2 Na/H 2 CFSO 2 Na via photoredox catalysis is described. This reaction exhibits broad functional group compatibility, providing the desired products in good yields. However, CF 3 SO 2 Na failed to produce the trifluoromethyl product. DFT calculations revealed that the transition state activation energy for radical trifluoromethylation was significantly higher and the isotropic charge repulsion makes it difficult for the CF 3 radical to transfer electrons.

An oxa-6π-electrocyclization of difluoroenoxysilanes with diaryl 2-indolylmethanols has been developed. In addition, a rarely reported C3-nucleophilic [3+2] cycloaddition of difluoroenoxysilanes with dialkyl 2-indolylmethanols has been disclosed. This divergent cycloaddition approach affording readily available difluoroenoxysilanes as three-atom and C2 synthons provides rapid access to fluoro 2 H -pyrano[3,4- b ]indoles and gem -difluoro cyclopenta[ b ]indoles in good to excellent yields with good functional group tolerance. The metal-free and mild conditions using only HFIP as the solvent without any external acid catalyst illuminate practical and environmentally benign advantages.

Difluoroenoxysilane, a commonly used difluoroallylating reagent, has attracted considerable attention in recent years. However, its application in the annulation reaction for the construction of fluorinated heterocyclic compounds remains relatively limited. Presented here is the Brønsted acid-catalyzed efficient formal [4 + 2] annulation of difluoroenoxysilanes with α-cyano chalcones. The developed protocol demonstrates tolerance to various substituents under mild reaction conditions, providing a reliable approach to construct gem -difluoro-3,4-dihydro-2 H -pyrans in good to excellent yields with high diastereoselectivities.

The photoredox-catalyzed 1,6-difluoromethylation of 3-methyl-4-nitro-5-styrylisoxazole with HCF 2 SO 2 Na has been developed. Structurally diverse difluoromethylated products were obtained in good yields, and their further transformations were also investigated. The di-, tri-, and monofluoromethylation of the substrates were compared, and the yield of the difluoromethylation was the highest. DFT calculations revealed that in the difluoromethylation reaction the CF 2 H radical was nucleophilic, and the transition state activation energy was the lowest.

A decarboxylative/dehydrofluorinative formal [3 + 2] cycloaddition aromatization of isoquinolinium N -ylides with difluoroenoxysilanes has been developed. This methodology provides a facile and straightforward synthetic pathway to afford highly functionalized fluorinated pyrrolo[2,1- a ]isoquinolines in good to excellent yields under mild conditions. Moreover, gram-scale and synthetic derivatization experiments for the late-stage functionalization of drug molecules have also been demonstrated.

A novel efficient HFIP-catalyzed synthesis of structurally diverse 2,2-difluoro-3-hydroxy-1,4-diketone derivatives from readily available glyoxal monohydrates and difluoroenoxysilanes is described. This convenient protocol is induced by the distinctive fluorine effect of the reactants and the fluoroalcohol catalyst, which represents the first application of fluoroalcohol catalysis in a Mukaiyama aldol reaction.

A hexafluoroisopropanol (HFIP)-catalyzed difluoroalkylation of propargylic alcohols with difluoroenoxysilanes to access structurally diverse tetrasubstituted difluoroalkyl allenes has been developed. This convenient procedure enables the rapid construction of highly functionalized multisubstituted fluorinated allenes in a mild and straightforward way. Furthermore, the synthetic potential of this methodology has been demonstrated by the facile synthesis of various structurally interesting fluorine-containing molecules such as gem -difluorosubstituted dihydropyran, tetrasubstituted CF 2 H-allene, and multisubstituted fluorinated cyclopentanone derivatives.

An efficient approach for the reversal of regioselectivity in the nucleophilic introduction of difluorinated carbanion into α,β-enones has been developed via a silylium catalysis. The strong electron-withdrawing properties and bulky substituents of in situ-generated silyl triflic imide catalyst is the key for the 1,4-addition reaction to proceed smoothly. The synthetic utility is highlighted by the further use of this method for the synthesis of 2,4,6-triarylsubstituted 3-fluoropyridines in a one-pot manner.

A general synthesis of 4-hydroxylcarbazoles by domino vinylogous conjugate addition/cyclization/elimination/aromatization of easily prepared 3-nitroindoles with alkylidene azlactones under mild and transition-metal-free conditions has been developed. This method was also applicable to other nitrosubstituted benzofused heterocycles such as 3-nitrobenzothiophene, 2-nitrobenzothiophene, and 2-nitrobenzofuran. The valuable tetracyclic carbazole derivatives, such as 6 H -oxazolo[4,5- c ]carbazole and 3,6-dihydro-2 H -oxazolo[4,5- c ]carbazol-2-one, were readily prepared from the product, demonstrating synthetic utility of this method., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

It is unclear that the changes and migration of coal-derived minerals on the graphitization process of coal. The Taixi anthracite is the study sample of the changes and migration mechanisms of coal-derived minerals during graphitization. Raw coal and different temperature-treated products were collected and analyzed by X-ray diffraction (XRD) to reflect the variation trends of the crystal structure and functional groups with temperature. To analyze the microstructure and mineral composition of the samples in experimental and industrial ultrahigh-temperature graphitization furnaces, a series of experiments were performed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). The results showed that temperature played a crucial role in the changes and migration of minerals during the graphitization of anthracite. As the temperature rose, cracks appeared from the surface to the inside of anthracite and minerals gradually changed and migrated from the inside of the anthracite to the cracks in the form of gas or liquid. At ultrahigh temperatures, only a small amount of silicon remains in the system as a catalyst, and most of the elements escaped in the form of oxides., Competing Interests: The authors declare no competing financial interest., (© 2020 The Authors. Published by American Chemical Society.)

The selective catalytic C-N bond cleavage of amides into value-added amine products is a desirable but challenging transformation. Molecules containing iminodibenzyl motifs are prevalent in pharmaceutical molecules and functional materials. Here we established a combined KOH/BEt 3 catalyst for deaminative hydroboration of acyl-iminodibenzyl derivatives, including nonheterocyclic carboxamides, to the corresponding amines. This novel transition-metal-free methodology was also applied to the construction of Clomipramine and luminophores.

A palladium-catalyzed tandem dehydrogenative [4 + 2] annulation of terminal olefins with N -sulfonyl amides via C(sp 2 )-H activation, allylic C(sp 3 )-H activation, and homoallylic C(sp 3 )-H elimination processes has been developed. Promoted by the DMSO ligand, various benzamides, heterocyclic arylamides, alkenyl carboxamides, and commercial olefins are found to be efficient substrates to construct important heterocyclic compounds bearing a vinyl substituent with high E stereoselectivity. Using air as the terminal oxidant also provides a great advantage regarding environmental friendliness.

A mild and general procedure for the difluoromethylation of organochalcogen compounds has been accomplished via sulfoxide and selenoxide-directed [3,3]-sigmatropic rearrangement/Haller-Bauer reaction with difluoroenoxysilanes. The reactions showed good functional group compatibility, wide substrate applicability, and facile scalability. The synthetic utility is highlighted by the iterative use of this protocol to construct multi-CF 2 H-containing chalcogenides and the late-stage modification of pharmaceuticals.

Bubble-particle attachment is the key step for successful flotation. Modeling of attachment interactions between air bubbles and particles after their collision can be analyzed using the Stefan-Reynolds model (immobile bubble surfaces) and the modified Stefan-Reynolds model (mobile bubble surfaces). However, these models have been rarely used, and the limitations of these models have not yet been reported. The objective of this paper is to address this matter under a wide range of experimental flotation conditions. It was found that the Stefan-Reynolds model can be used to determine the real bubble-particle hydrophobic constants at low surfactant concentrations. However, at high surfactant concentrations, the real bubble-particle hydrophobic constants cannot be determined, but the fictive bubble-particle hydrophobic constants can be obtained by using the linear extrapolation method. The same analysis was also performed using the modified Stefan-Reynolds model. The results showed that the attachment of quartz particles to air bubbles in the presence of dodecyl amine hydrochloride is accelerated due to the mobility of the air-water interface. This paper demonstrated that the limitations of the Stefan-Reynolds model and the modified Stefan-Reynolds model to analyze the bubble-particle attachment interactions can be addressed by introducing the fictive bubble-particle hydrophobic constants.

A highly regio- and stereoselctive palladium-catalyzed domino reaction of functionalized aryl allyl ethers has been developed. Various aryl allyl ethers derived from the phosphine-catalyzed addition of electron-deficient allenes with phenol are found to be efficient substrates for the synthesis of 2-substituted 2,3-dihydrobenzofurans and indolines. It is the first example of aryl allyl ether used as an ideal and practical precursor of hard to get functionalized 1,3-butadiene for the heterocyclic compound synthesis.

An array of novel 1,4-diazobicyclo[2.2.2]octane (DABCO) based ionic liquids were developed and used as recyclable catalysts for the aza-Michael addition at room temperature without any organic solvent. [DABCO-PDO][OAc] was found to be the most efficient catalyst, and the amount of catalyst was only 10 mol %. Various amines reacted with a wide range of α,β-unsaturated amides, smoothly affording target products in good to excellent yields within hours. Moreover, the catalyst could be reused up to eight times, still maintaining a high catalytic activity. Finally, a plausible mechanism was proposed. FTIR and computational chemistry were used to verify the catalytic mechanism.