Recent advances in C-F bond activation of trifluoromethylated carbonyl compounds and derivatives.

The selective activation of inert C-F bonds is one of the most challenging topics in modern organic chemistry. Trifluoromethylketones represent a class of versatile building blocks that are inexpensive and readily available polyfluorinated starting materials. The functionalization of C-F bond in trifluoromethylketones has recently been achieved using difluoroenolates, difluorinated acyl anions or radicals for the synthesis of difluoromethylene compounds. This strategy has also been successfully applied to their derivatives, such as trifluoromethylated esters, amides, diazo compounds and N-sulfonylhydrazones, which would be of significant value for the synthesis of partially fluorinated intermediates. In this review, we mainly focus on the recent advances, challenges and perspectives of trifluoromethylated carbonyl compounds and their derivatives via C-F bond activation, along with mechanistic insight.

Photochemical and Electrochemical Strategies for Hydrodefluorination of Fluorinated Organic Compounds.

Hydrodefluorination (HDF) is a very important fundamental transformation for conversion of the C-F bond into the C-H bond in organic synthesis. In the past decade, much progress has been achieved with HDF through the utility of low-valent metals, transition-metal complexes and main-group Lewis acids. Recently, novel methods have been introduced for this purpose through photo- and electrochemical pathways, which are of great significance, due to their considerable environmental and economical advantages. This Review highlights the HDF of fluorinated organic compounds (FOCs) through photo- and electrochemical strategies, along with mechanistic insights.

Recent advances in the synthesis and applications of α-(trifluoromethyl)styrenes in organic synthesis.

α-Trifluoromethylstyrene derivatives are versatile synthetic intermediates for the preparation of more complex fluorinated compounds. Much attention has been paid to these compounds by the organic chemistry community, because they have been successfully utilized in C-F bond activation in a CF3 group, mainly including anionic SN2'-type substitution, cationic SN1'-type substitution, ipso-substitution and defluorinative functionalization with transition metals or photoredox catalysts. In addition, transition metal-catalyzed cycloaddition reactions of α-trifluoromethylstyrenes have been developed for the construction of cycloalkanes and cycloalkenes containing fluoro or trifluoromethyl groups. In this review, we systematically summarized the synthesis of α-trifluoromethylstyrenes and their applications in organic synthetic chemistry, and their mechanisms were also discussed.

Recent advances in the direct functionalization of quinoxalin-2(1H)-ones.

The direct C3-functionalization of quinoxalin-2(1H)-ones via C-H bond activation has recently attracted considerable attention, due to their diverse biological activities and chemical properties. This review will focus on the recent achievements, mainly including arylation, alkylation, acylation, alkoxycarbonylation, amination, amidation and phosphonation of quinoxalin-2(1H)-ones. Their mechanisms are also discussed.

Copper-mediated trifluoroacetylation of indoles with ethyl trifluoropyruvate.

Direct trifluoroacetylation of indoles with ethyl trifluoropyruvate as a trifluoroacetylating reagent has been developed. This novel protocol provides an attractive route for the preparation of 3-trifluoroacetylindole derivatives, due to its operational simplicity and practicability as well as mild reaction conditions.

Recent advances in reactions of aryl sulfonyl isocyanates.

Aryl sulfonyl isocyanates are important intermediates in organic synthesis. They are used as electrophilic reagents and easily react with nucleophiles to form amides, sulfonyl ureas, pyrrolidine derivatives, lactams, oxazolidinones, and so on. Although there are some reviews on the applications of isocyanates in chemistry, few are concerned about aryl sulfonyl isocyanates. This review focuses on recent advances related to aryl sulfonyl isocyanates in organic synthesis, mainly including three special characteristics. The mechanisms of the typical reactions are also discussed.

Diverse sp(3) C-H functionalization through alcohol ß-sulfonyloxylation.

Site-selective C-H functionalization has emerged as an attractive tool for derivatizing complex synthetic intermediates, but its use for late-stage diversification is limited by the functional groups that can be introduced, especially at unactivated sp(3)-hybridized positions. To overcome this, we introduce a strategy that directly installs a sulfonyloxy group at a ß-C-H bond of a masked alcohol and subsequently employs nucleophilic substitution reactions to prepare various derivatives. Hydroxyl groups are widely found in bioactive molecules and are thus readily available as synthetic handles. A directing group is easily added (and subsequently removed) from the alcohols such that a formal site-selective ß-C-H sulfonyloxylation of these alcohols is achieved. Substitution reactions with carbon, nitrogen, oxygen and other nucleophiles then lead to diverse functionalizations that may help to streamline the synthesis of complex analogues for drug discovery.

Decarboxylative functionalization of cinnamic acids.

Decarboxylative functionalization of α,ß-unsaturated carboxylic acids is an emerging area that has been developed significantly in recent years. This critical review focuses on the different decarboxylative functionalization reactions of cinnamic acids leading to the formation of various C-C and C-heteroatom bonds. Apart from metal carboxylates, decarboxylation in cinnamic acids has been achieved efficiently under metal-free conditions, particularly via the use of hypervalent iodine reagents. We believe this review will encourage organic chemists to develop vinylic decarboxylation in a more appealing way with an understanding of new mechanistic insight.

Analysis of poly-ß-hydroxyalkonates (PHA) during the enhanced biological phosphorus removal process using FTIR spectroscopy.

Enhanced biological phosphorus removal (EBPR) is the main phosphorus removal technique for wastewater treatment. During the anaerobic-aerobic alternative process, the activated sludge experienced the anaerobic storage of polyhydroxy-ß-alkonates (PHA) and aerobic degradation, corresponding the infrared peak intensity of sludge at 1 740 cm(-1) increased in the aerobic phase and declined in the anaerobic phase. Compared with PHA standard, this peak was indentified to attribute the carbonyl of PHA. The overlapping peaks of PHA, protein I and II bands were separated using Gaussian peak fitting method. The infrared peak area ratios of PHA versus protein I had a good relationship with the PHA contents measured by gas chromatography, and the correlation coefficient was 0.873. Thus, the ratio of the peak area of PHA versus protein I can be considered as the indicator of the PHA content in the sludge. The infrared spectra of 1 480-1 780 cm(-1) was selected, normalized and transferred to the absorption data. Combined with the chromatography analysis of PHA content in the sludge sample, a model between the Fourier-transform infrared spectroscopy (ETIR) spectra of the sludge and PHA content was established, which could be used for the prediction of the PHA content in the unknown sample. The PHA content in the sludge sample could be acquired by the infrared spectra of the sludge sample and the established model, and the values fitted well with the results obtained from chromatograph. The results would provide a novel analysis method for the rapid characterization and quantitative determination of the intracellular PHA content in the activated sludge.

Efficient silver-catalyzed direct sulfenylation and selenylation of rich arenes.

An efficient protocol for silver/copper-cocatalyzed direct sulfenylation and selenylation of arenes with aryl disulfides and diselenides has been developed. This strategy exhibits excellent functional group tolerance and high regioselectivity. Mono sulfenylation and selenylation products can be exclusively achieved. This reaction provides a simple and practical route to the preparation of aryl sulfides and selenides.

Recent advances in the synthesis of nitroolefin compounds.

Development of methodology for the preparation of nitroolefins is of significant interest to organic chemists. Recently, numerous useful methods have been developed, mainly including direct nitration of olefinic C-H bonds, nitro-decarboxylation of aromatic α,ß-unsaturated carboxylic acids, ipso-nitration of vinylboronic acids and multidehydrogenative cross-coupling reaction of (hetero)arenes with nitroethane. This review will focus on recent achievements in nitroolefin synthesis and the mechanisms of the reactions are also discussed.

Synthetic applications of arylboronic acid via an aryl radical transfer pathway.

The transition-metal-catalyzed functionalization of arylboronic acids is the most powerful tool for the formation of carbon-carbon and carbon-heteroatom bonds in modern organic synthesis. These transformations are generally considered to proceed via organometallic intermediates generated by transmetalation from the boronic acids. Interestingly, there is a novel recognition that arylboronic acids can serve as aryl radical precursors via oxidative carbon-boron bond cleavage in recent years. Manganese(III) acetate, Ag(I)/persulfate and iron(II or III)/persulfate catalytic systems have been shown to be effective for this transformation. In this review, recent advances in this new area are highlighted and their mechanisms are also discussed.

Transition-metal-catalyzed additions of C-H bonds to C-X (X = N, O) multiple bonds via C-H bond activation.

Chemical transformations via catalytic C-H bond activation have been established as one of the most powerful tools in organic synthetic chemistry. Transition-metal-catalyzed addition reactions of C-H bonds to polar C-X (X = N, O) multiple bonds, such as aldehydes, ketones, imines, isocyanates, nitriles, isocyanides, carbon monoxide and carbon dioxide, have undergone a rapid development in recent years. In this review, recent advances in this active area have been highlighted and their mechanisms have been discussed.

Recent advances in the synthesis of aromatic nitro compounds.

Aromatic nitro compounds are important intermediates in synthetic organic chemistry as well as in the chemical industry. Numerous useful methods for their preparation have been developed in recent years. In this review, recent advances in the synthesis of aromatic nitro compounds are summarized, including the nitration of aromatic hydrocarbons, aryl boronic acids, aryl halides and pseudohalides, aryl carboxylic acids and the oxidation of aryl primary amines and azides. Their mechanisms are discussed.

Nano-Fe(2)O(3)-catalyzed direct borylation of arenes.

Nano-Fe(2)O(3)-catalyzed borylation of arenes with diboron pinacol ester B(2)pin(2) has been found to give borylation products with selectivity controlled by electronic effects of substituents.

Palladium-catalyzed direct cyanation of indoles with K(4)[Fe(CN)(6)].

Direct cyanation of indole derivatives has been achieved with nontoxic K(4)[Fe(CN)(6)] as cyanating agent through Pd-catalyzed C-H bond activation.

Arylation and vinylation of alpha-diazocarbonyl compounds with boroxines.

An alternative approach for alpha-arylation and alpha-vinylation of carbonyl compounds is described: reaction between aryl- or vinylboroxines with alpha-diazocarbonyl compounds leads to the formation of alpha-arylated or alpha-vinylated carbonyl compounds under mild conditions.

Solubility of silybin in aqueous poly(ethylene glycol) solution.

Silybin is a main component in silymarin, which is an antihepatotoxic polyphenolic substance isolated from the milk thistle plant, Silybum marianum. A major problem in the development of an oral solid dosage form of this drug is the extremely poor aqueous solubility. In present work, the solubility of silybin in aqueous poly(ethylene glycol) 6,000 (PEG 6,000) solution at the temperature range from 293.15 to 313.15K was measured by a solid liquid equilibrium method. The aim of this study is to investigate the possible effect of poly(ethylene glycol) concentration and temperature on the solubility of the drug, and to reveal the solubilization capacity of the polymer for the drug. Experimental results reveal that the solubility of silybin increases with the increase both in PEG's concentration and temperature. With the increase in PEG's concentration, the transfer enthalpy and entropy for silybin from water to aqueous PEG solution increases first in a positive region, and then decreases to a negative region. The transfer enthalpy is lower than the entropy term. A modified Universal Quasi Chemical (UNIQUAC) model was used to correlate solubility data.

Viscosity B-coefficients and activation parameters for viscous flow of a solution of heptanedioic acid in aqueous sucrose solution.

Viscosity and density data for the system of heptanedioic acid dissolved in aqueous sucrose solution at temperature range from 288.15 to 313.15 K have been measured. The viscosity B-coefficients for heptanedioic acid in aqueous sucrose solution has been calculated. The effect of temperature and sucrose concentration on the B-coefficients is discussed. On the basis of the Feakins equation, the activation parameters (Deltamu3++, DeltaH3++, DeltaS3++, DeltaG12(0)++, DeltaH12(0)++ and DeltaS12(0)++) for viscous flow of the solution have been evaluated, together with the Gibbs energy of transfer for the solute from the ground state solvent to the hypothetical viscous transition state solvent (DeltaG3++(1-1')). The effect of sucrose concentration and temperature on the activation parameters has been discussed.