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For many years since its discovery, Selenium has played the role of a bad boy who became a hero in organic transformations. Selenium dioxide, for instance, is one of the most remembered reagents in allylic oxida-tions, having been applied in the synthesis of several naturally occurring products. The main goal of this review is to show the recent advances in the use of classical and new selenium reagents in organic synthesis. As demon-strated through the around 60 references discussed here, selenium can go even forward as a versatile reagent. We bring a collection of selenium reagents and their transformations that still asleep in the eyes of most synthetic or-ganic chemists.

Oxygen ligation is envisioned to provide a stable and distinctive coordination environment to the strongly oxophilic rare-earth metals. However, the well-defined dialkyl complexes bearing oxyanion ancillary ligand had been rarely addressed for the instability of the complexes and the shortage of easily available ligands. Herein, we report the synthesis of phosphate ligated dialkyl yttrium complexes (PYR2) featuring a high stability and a tunable ligand. Treated with the borate reagent, the phosphate yttrium complex displays high activity and selectivity in the catalytic cis-1,4-polymerization of isoprene (up to 96.5%). Furthermore, using AlMe3 as an additive, the stereoselectivity switches to trans-1,4-polymerization (up to 92.0%).

The tandem reaction of photoinduced double hydrogen-atom transfer and deoxygenative transborylation for chemo- and site-selective reduction of nitroarenes into aryl amines under catalyst-free, room temperature conditions was disclosed in excellent yields. In this reaction, isopropanol (iPrOH) was used as hydrogen donor and tetrahydroxydiboron [B2(OH)4] as deoxygenative reagent with green, cheap, and commercially available credentials. In particular, a wide range of reducible functional groups such as halogen (-Cl, -Br, and even -I), alkenyl, alkynyl, aldehyde, ketone, carboxyl, and cyano are tolerated. Moreover, the reaction preferentially reduces the nitro group at the electron-deficient site over another nitro group in the same molecule. A detailed mechanistic investigation in combination of experiments and theoretical calculations gave a reasonable explanation for the reaction pathway.

Sulfonic-containing UiO-66 and MIL-101 MOF materials, prepared by direct synthesis with a sulfonic acid-including benzene dicarboxylate (SO3H-BDC) linker, have been evaluated as acid catalysts in Friedel–Crafts acylation of anisole with acetic anhydride. The catalytic activity of these materials was compared to other conventional acidic sulfonic heterogeneous catalysts, such as commercial Nafion-SAC-13 and Amberlyst-15. The catalytic performance of MOF materials was significantly dependent on their textural properties and the availability of sulphonic acid groups. MIL-101-SO3H material displayed a remarkable anisole conversion and specific activity per sulfonic acid centre due to its open structure and multimodal pore size distribution. The inherent properties of MIL-101-SO3H material allowed a more sustainable catalyst regeneration than those used for conventional heterogeneous catalysts due to the deposition of reagents and products, in particular poly-acetylated compounds. MIL-101-SO3H proved an easy recovery and reusability in successive runs without any loss of activity. These promising results evidenced the potential of MIL-101-SO3H as an alternative catalyst for acid-catalyzed reactions.

Although fluorobis(phenylsulfonyl)methane (FBSM) and its cyclic analog 2-fluoro-1,3-benzodithiole-1,1,3,3-tetraoxide (FBDT) possess similar physicochemical properties, Shibata et al. found that FBSM failed to undergo nucleophilic monofluoromethylation of aldehydes regardless of the reaction conditions attempted (using various organic and inorganic bases). However, it was later discovered by Hu et al. that the nucleophilic monofluoromethylation could be accomplished by employing lithium hexamethyldisilazide (LiHMDS) as a base. Herein, we present an in-depth computational investigation into the intriguing effects of reagent structure and bases on the nucleophilic monofluoromethylation of aldehydes. The computations reveal the 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed nucleophilic monofluoromethylation of benzaldehyde with acyclic FBSM is a thermodynamically unfavorable process mainly due to the destabilizing O•••O lone pair repulsions in FBSM product, whereas such repulsion could be largely avoided in FBDT product because of its constrained five-membered ring structure. Employing LiHMDS as a base cannot only facilitate the nucleophilic monofluoromethylation via Li–O interactions but also render the monofluoromethylation of benzaldehyde with FBSM thermodynamically favored.

The green catalytic system (Al2O3/H2O2/ethyl acetate) used in the oxidation of (R)-limonene has many advantages since the reagents have low cost, it is toxicity-free (no heavy metals and no toxic solvents are utilized), and water is the only by-product. The synthesized epoxide may have applications in several industrial segments like adhesives, polymers, resins, and others that require a clean process, especially as a precursor for medical biomaterial applications. An experimental design 23 with 17 assays (6 axial points and central point triplicate) has been carried out for the optimization of the conversion and selectivity towards limonene diepoxide. The assessed variables included the quantities of alumina, limonene, and hydrogen peroxide (70% aq). The analysis of variance (ANOVA) confirmed the validity of the mathematical model obtained with a 90% confidence interval in the studied range. The conversion and selectivity towards limonene diepoxide was >99%, with a reaction time of 10 h, showing the high efficiency of this catalytic system. FTIR, Raman, GC/MS, 1H, 13C, and HSQC NMR techniques confirmed the structure of the synthesized and purified limonene diepoxide.

Esterification reaction is a pretreatment method used to reduce the free fatty acids (FFA) content in acidified oil. Normally, the presence of high FFA content contributes to saponification reaction and thus, decreases the yield of fatty acid methyl ester (FAME) produced. The usage of ion exchange resin (IER) as a catalyst has been widely used to reduce the FFA content because they can catalyse the esterification reaction under mild conditions. However, current IER are having low acidic acid sites, moderate surface area and low thermal stability. This study focuses on the esterification process of FFA in simulated used cooking oil (SUCO) using self-synthesised sulphonated hypercrosslinked exchange resin (SHER) as catalyst. This study was divided into two stages. The first stage focused on the synthesis and characterisation of SHER, prepared via non-aqueous dispersion (NAD) technique followed by sulphonation process. The effect of monomer/co-monomer concentration, crosslinker concentration, Lewis acid catalyst ratio, and sulphonation reagent on the physicochemical characterisation of the resin were investigated to produce the best catalyst beads. From this stage, the best SHER beads has successfully developed at the condition of 80% of styrene (St), 20% of vinylbenzyl chloride (VBC), 1wt% of ethylene glycol dimethacrylate (EGDMA), 1:1 of molar ratio of FeCl3: CH2Cl, and 4wt% of sulphuric acid. The newly developed SHER possesses a high surface porosity with approximately 836 m2 g-1 surface area. It has the ability to withstand high temperature up to 398°C with the acidity values at 5.1 mmol g-1. The second stage concentrated on the performance of SHER in the esterification of FFA using SUCO as a feedstock. The esterification reaction was carried out in a batch system and the effect of various parameters such as catalyst loading, temperature, and molar ratio were investigated. SHER had successfully catalysed the reaction and achieved 97% of FFA conversion at 150 rpm, 5wt% of catalyst loading, 60°C, and 12:1 of methanol (MeOH) to SUCO molar ratio. During reusability study, the catalyst activity decreased for about 40% after five cycles of reaction. The decrease in FFA conversion was due to the pore blockage during the reaction and hence, blocked the reactants from accessing the active sites. The performance of SHER was compared with selected commercial resins (i.e., Diaion RCP145H, Diaion PK228LH, and Diaion SK1BH) and the experiments were conducted at the same reaction conditions. SHER showed the highest conversion and reaction rate compared to other catalysts. The excellence performance of SHER was due to the high amount of surface area, pore volume, sulphur content, and acidity owned by the SHER.

Carbon–carbon bond formation is the core of organic synthesis, in which organometallic reagents play the key role in the forms of 1,2-nucleophilic additions, conjugate additions, and transition-metal catalyzed cross-couplings. These reactions have enabled the production of a wide range of organic molecules in our society. Despite the enormous power of organometallic reagents in chemical synthesis, they have inherent drawbacks in the eyes of future sustainability. This account summarizes our efforts over the past three decades on the exploration of new scientific means to overcome the drawbacks and limitations of these classical organometallic reactions.

Phosphate residue is a kind of hazardous solid waste and if not properly disposed of, could cause serious environmental contaminations. The abundant iron salt available in phosphate residue can be used to prepare photo-Fenton catalytic reagent for wastewater treatment. In this study, the phosphate residue was effectively purified by a hydrothermal recrystallization method, reaching an iron phosphate purity of 94.2%. The particles of iron phosphate were further processed with ball milling with their average size reduced from 19.4 to 1.6 μm. By hydrothermal crystallization of iron phosphate and thermal decomposition of oxalate precursor, porous iron hydroxy phosphate was prepared. The modified porous iron hydroxy phosphate (m-PIHP) of higher surface area with iron oxalate on its surface can degrade 98.87% of Rhodamine B in 15 min. Cyclic experiment showed that the catalyst still had a good catalytic activity after six cycles (>40%). The X-ray photoelectron spectroscopy results showed that the iron oxalate complex on the catalyst surface decomposed to produce ferrous ions and accelerated the rate of •OH production. The current work demonstrated that the m-PIHP synthesized from phosphate residue and modified with iron oxalate can be used as an effective dye wastewater treatment agent.

Cerium-promoted silica supported copper chromite catalyst was synthesized from acid hydrolysis of sodium silicate by sol–gel method. The catalyst was characterized by Brunauer–Emmett–Teller (BET) method, field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD) and pyridine adsorbed Fourier transform infrared spectroscopy (Py-FTIR). Among cerium doped catalysts, 5 wt% of Ce promoted copper chromite supported by 40 wt% of silica (SiCuCr40–Ce5) shows the largest BET surface area. XRD analysis of the reduced form of the catalyst shows both CeO2/Ce2O3 redox system and CuO/Cu2O/Cu redox system. Py-Fourier shows the maximum number of Lewis acid sites for SiCuCr40–Ce5 than others. The highest acetol selectivity with analytical reagent (AR) grade glycerol conversion is observed for SiCuCr40–Ce5 at 200 °C for 3 h in a batch reactor at atmospheric pressure. Cerium promotion lowers the reaction temperature with enhanced glycerol conversion and increased acetol selectivity. Though the above catalyst shows higher conversion for laboratory reagent (LR) grade glycerol but it reduces acetol selectivity. The addition of glucose into the LR grade glycerol further reduces glycerol conversion and decreases the acetol selectivity to zero. This may be due to the presence of iron as impurity in LR grade glycerol. XRD analysis of spent catalyst shows the absence of redox catalytic system and the pore volume reduces identified by BET analysis. Raman analysis of the spent catalyst shows graphite-like carbon deposition in the spent catalyst.

A series of Beta zeolite catalysts with controllable particle sizes and similar Si/Al ratios were prepared by introducing imidazole (IMD) into the synthesis system and used for a liquid-phase transalkylation of diethylbenzene (DEB) with benzene (Bz). Beta zeolite catalyst prepared with IMD/SiO2 molar ratio of 0.5 possessed the smallest particle size (mean particle size of 119 nm) and the highest DEB conversion of 79.16%, under the reaction conditions: 260 oC, 4.0 MPa, WHSV (diethylbenzene) of 2.0 h-1, W(benzene)/W(diethylbenzene) of 3/1, time on stream of 5 h. Then, for the purpose of elucidating the catalytic roles of the acid sites with different strength, types and positions in Beta zeolite in the transalkylation reaction, we carried out Na+ loading on the prepared Beta zeolite to eliminate strong acid sites, and poisoned Bronsted acid sites and external acid sites by using 2,4-dimethylquinoline (2,4-DMQ) and triphenylphosphorus (TPP) as toxic reagents, respectively. The results suggested that the moderate and strong Bronsted acid sites of Beta-IMD0.5 were the active sites for the liquid-phase transalkylation of DEB with Bz and their utilization rate showed a trend of increased first and then decreased. Significantly, 31% of the external Bronsted acid sites of Beta-IMD0.5 contributed 81% of DEB conversion. The external acid sites had more contribution to the reaction, due to the short diffusion path and fine accessibility.

Nanocomposite Cu–Mn–O nano-particle (CuMnNP) and nano-sheet (CuMnNS) catalyst were successfully prepared using a one-step hydrothermal method in the absence of any templating reagent. Materials were characterised applying various structural techniques. SEM images showed that composite Cu–Mn oxide sheets were tailor-made synthesised by a one-pot urea-abetted protocol. Conversely, upon replacing carbamate by Na2CO3, oxidised metal Cu–Mn particles could be obtained. The formation of bulk mixed Cu–Mn phases resulted in an enhanced crystal lattice oxygen reactivity in CuMnNS. XPS, XRD and TPR measurements confirmed the presence of the Cu+ and Cu2+ species in nano-catalysts, and CuMnNS nanomaterials possessed more surface defects, thus causing a higher O2 adsorption/storage capacity. CuMnNS presented a superior catalytic activity as opposed to CuMnNP in the preferential oxidation (PROX) pathway of CO. With both CO2 and H2O in feed, a decrease in CO turnover was observed, due to a competitive interface binding of CO, CO2 and H2O. Compared to CuMnNP, CuMnNS also demonstrated a high time-on-stream conversion of methanol for the reforming for all operating conditions.

α‑Amino acids such as glycine derivatives have been commonly utilized as reagents for decarboxylative functionalization. In contrast to previous reports that require transition-metals and organic dyes to promote this process, we herein report a catalyst-free approach for the decarboxylative amination of glycine derivatives with azo compounds under visible-light irradiation. A range of important aminals are achieved under mild reaction conditions with high efficiency.

Chiral carboxylic acids bearing an α-stereogenic center constitute the backbone of many natural products and therapeutic reagents as well as privileged chiral ligands and catalysts. Hence, it is not surprising that a large number of elegant catalytic asymmetric strategies have been developed toward the efficient synthesis of α-chiral carboxylic acids, such as α-hydroxy acids and α-amino acids. In this review, the recent advances on asymmetric synthesis of α-stereogenic free carboxylic acids via organocatalysis and transition metal catalysis are summarized (mainly from 2010 to 2020). The content is organized by reaction type of the carboxyl source involved, including asymmetric functionalization of substituted carboxylic acids, cyclic anhydrides, α-keto acids and substituted α,β-unsaturated acids and so on. We hope that this review will motivate further interest on catalytic asymmetric synthesis of chiral α-substituted carboxylic acids.

Direct comparison of homologous molecules provides a foundation from which to elucidate both subtle and patent changes in reactivity patterns, redox processes, and bonding properties across a series of elements. While trivalent molecular U chemistry is richly developed, analogous Np or Pu research has long been hindered by synthetic routes often requiring scarcely available metallic-phase source material, high-temperature solid-state reactions producing poorly soluble binary halides, or the use of pyrophoric reagents. The development of routes to nonaqueous Np3+/Pu3+ from widely available precursors can potentially transform the scope and pace of research into actinide periodicity. Here, aqueous stocks of An4+ (An = Np, Pu) are dehydrated to well-defined [AnCl4(DME)2] (DME = 1,2-dimethoxyethane), and then a single-step halide exchange/reduction employing Me3SiI produces [AnI3(THF)4] (THF = tetrahydrofuran) in a high to nearly quantitative crystalline yield (with I2 and Me3SiCl as easily removed byproducts). We demonstrate the synthetic utility of these An-iodide molecules, prepared by metal0-free routes, through characterization of archetypal complexes including the tris-silylamide, [Np{N(SiMe3)2}3], and bent metallocenes, [An(C5Me5)2(I)(THF)] (An = Np, Pu)─chosen because both motifs are ubiquitous in Th, U, and lanthanide research. The synthesis of [Np{N(Se═PPh2)2}3] is also reported, completing an isomorphous series that now extends from U to Am and is the first characterized Np3+-Se bond.

We report on an operationally simple catalytic method for the tungsten-catalyzed hydrogenation of quinolines through the use of the easily handled and self-contained precursor [WCl(η5-Cp)(CO)3]. This half sandwich complex is indefinitely storable on the bench in simple screw-capped bottles or stoppered flasks and can, if required, be prepared on a multi-gram scale while the actual catalytic transformations were performed in the presence of a Lewis acid in order to achieve both decent substrate conversions and product yields. The described method represents a facile and atom-efficient access to a variety of 1,2,3,4-tetrahydroquinolines that circumvents the use of cost-intensive and oxygen-sensitive phosphine ligands as well as auxiliary hydride reagents.

Manganese dioxide (α-MnO2) and graphene oxide (GO nanocomposites were prepared and successfully characterized using Fourier-transform infrared (FT-IR), field emission scanning-electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX) mapping methods and Xray diffraction (XRD) analyses. This reagent is an efficient catalyst for the aerobic oxidation of trimethylsilyl (TMS), tetrahedropyranyl (THP), and methoxymethyl ethers (MOM) to their corresponding carbonyl compounds in the presence of K2CO3. All reactions were performed in n-hexane under mild and completely heterogeneous reaction conditions. Our novel method has the advantages of excellent yields, short reaction times, availability and reusability of the catalyst and simple and easy work-up procedure compared to the conventional methods reported in the literature.

The functional copper nanocomposites (Cu NCs) have received increasing attention in the environmental catalysis application for wastewater treatment due to their superior catalytic activity and reactivity. However, overcoming the pH limitations towards the neutral and alkaline wastewater remains a tricky challenge. In this work, we demonstrate a green strategy to synthesize Cu NCs with coexistence of active Cu, Cu2O and ZrO2 by self-propagating combustion of metallic glassy ribbons, which exhibit the extremely superior catalytic performance for degradation reaction, providing full conversion of organic dyes completely to the environmental friendly small species (efficiency > 99%) under acidic, neutral and alkaline conditions. Compared with all other catalysts developed thus far, the novel Cu NCs catalysts with more active sites present much enhanced catalytic capability of degradation efficiency without the use of any chemical reagents for neutral and alkaline organic dye solutions. The possible decomposition pathways of organic dyes for different pH systems were systematically investigated. More importantly, the two kinds of catalytic mechanism related to high reactivity of nanoscale Cu/Cu2O and strong oxidizing capability of activated •OH /•O2− radicals can also be successfully confirmed under different pH conditions. The green synthetic approach can be extended to design the various M-based nanocomposites (M = Fe, Co, Ni, Ag, Pd) as efficient catalysts for the functional applications of many chemical reactions.

A range of C2-phosphonylated sugars have been accessed through a palladium-catalyzed Hirao cross-coupling on 2-iodoglycals using trialkylphosphites as phosphorylating reagents. The developed conditions led to the creation of an unnatural C–P bond on sugars and proved to be compatible with diversely protected glycals (acetyl-, benzyl-, PMB-protected) as well as with unprotected substrates. Several monosaccharides and one disaccharide have been synthesized by applying this methodology. Deprotection conditions are also described.

Relative rates for the Lewis base-catalyzed acylation of aryl-substituted 1,2-diols with anhydrides differing in size have been determined by turnover-limited competition experiments and absolute kinetics measurements. Depending on the structure of the anhydride reagent, the secondary hydroxyl group of the 1,2-diol reacts faster than the primary one. This preference towards the secondary hydroxyl group is boosted in the second acylation step from the monoesters to the diester through size and additional steric effects. In absolute terms the first acylation step is found to be up to 35 times faster than the second one for the primary alcohols due to neighboring group effects.

A Negishi cross-coupling of α-hydroxy ester derivatives and arylzinc reagents has been developed. This reaction tolerates both primary and secondary C(sp3)-O alcohol precursors and achieves efficient cross-coupling under Ni catalysis without the need for added external metal reductant, photocatalyst, or additives. The arylation of readily accessible C(sp3)-O electrophiles in this operationally simple, rapid, and mild reaction provides a complementary way of accessing desirable α-aryl ester products.

An eco-friendly protocol to synthesize nitriles from their corresponding aromatic and aliphatic aldehydes in excellent yields has been developed. This is a catalyst-free protocol which employs an aminating reagent (MsONH3OTf) under mild conditions. The hydroxylamine triflic acid salts (MsONH3OTf) acted as the N source for this protocol. Our protocol proved to be easy to perform and presented good functional group tolerance.

A simple photochemical, nickel-catalyzed synthesis of ketones starting from carboxylic acids is presented. Hantzsch-ester (HE) functions as a cheap, green and strong photoreductant upon visible-light excitation to facilitate radical generation and also engages in the Ni-catalytic cycle to restore the reactive species. With this dual role, HE allows for the coupling of a large variety of radicals (1°,2°, benzylic, α-oxy & α-amino) with aroyl and alkanoyl moieties, a new feature in the synthesis of ketones through dual nickel photoredox catalysis. With both precursors deriving from abundant carboxylic acids, this protocol is a welcome addition to the organic chemistry toolbox. The reaction proceeds under mild conditions without the need for toxic metal reagents or bases and shows a wide scope, including pharmaceuticals and complex molecular architectures.

The hydrochlorination, hydrobromination, and hydroiodination of unactivated alkenes using methanesulfonic acid and inorganic halide salts (CaCl2, LiBr, LiI) in acetic acid are reported. This approach uses readily available and inexpensive reagents to provide the alkyl halides in up to 99% yield. An example of deuteriochlorination using deuterated acetic acid as the solvent is also demonstrated.

The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C–C cleavage to remove the acyl moiety, followed by Cu-mediated oxidative elimination to form an alkene between the α and β carbons. The newly-adopted N’-methylpicolinohydrazonamide (MPHA) reagent is key to enable efficient cleavage of ketone C–C bonds at room temperature. Diverse alkyl- and aryl-substituted olefins, dienes, and special alkenes are generated with broad functional group tolerance. Strategic applications of this method are also demonstrated.

A facile and regioselective synthesis of quinoxalines, an important motif in medicinal chemistry and materials sciences, was developed. Despite their prospective utility, the regioselective preparation of trisubstituted quinoxalines has not been previously established. In the reported system, hypervalent iodine reagents catalyzed the annulation between α-iminoethanones and o-phenylenediamines in a chemo/regioselective manner to afford trisubstituted quinoxalines. Excellent regioselectivities (6:1 to 1:0) were achieved using [bis(trifluoroacetoxy)iodo]benzene and [bis(trifluoroacetoxy)iodo]pentafluorobenzene as annulation catalysts.

We have developed a deaminative-decarboxylative protocol to form new carbon(sp3 )-carbon(sp3 ) bonds from activated amines and carboxylic acids. Amines and carboxylic acids are ubiquitous building blocks, available in broad chemical diversity and at lower cost than typical C-C coupling partners. To leverage amines and acids for C-C coupling, we developed a reductive nickel-catalyzed cross-coupling utilizing building block activation as pyridinium salts and redox-active esters, respectively. Miniaturized high-throughput experimentation studies were critical to our reaction optimization, with subtle experimental changes such as order of reagent addition, composition of a binary solvent system, and ligand identity having a significant impact on reaction performance. The developed protocol is used in the late-stage diversification of pharmaceuticals while more than one thousand systematically captured and machine-readable reaction datapoints are reposited.

The borane FmesBH2 reacts in a three-component reaction with an isonitrile and a small series of organonitriles to give rare examples of the class of dihydro-1,4,2-diazaborole derivatives. In a related way, annulated BN-indolizine derivatives became conveniently available, as were dihydro-1,4,2-oxaza- or thiazaborole derivatives. The nucleophilic framework of a dihydro-1,4,2-diazaborole example allowed for an uncatalyzed acylation reaction. It also served as a 1,3-dipolar reagent and underwent a [3+2] cycloaddition/[4+2] cycloreversion sequence when treated with methyl propiolate to give the respective pyrrole product. The [3+2] cycloaddition product of a dihydro-1,4,2-diazaborole derivative with N-phenylmaleimide was isolated and its heterobicyclo[2.2.1]heptane derived structure characterized by X-ray diffraction.

Pd-catalyzed allylative dearomatisation of naphthyl halides is shown to be feasible by employing Grignard reagents. The high reactivity of the nucleophile allows for fast reactions and low catalyst loading, while a plethora of successfully substituted compounds illustrate the broad scope. Five membered heteroaromatic compounds are also demonstrated to be reactive under similar conditions., Dearomatisation of benzylic halides have been achieved using Grignard reagents resulting in good isolated yields in short reaction times.

Perfluoro-tert-butylation reaction has long remained a challenging task. We now report the use of 1,1-dibromo-2,2-bis(trifluoromethyl)ethylene (DBBF) as a practical reagent for perfluoro-tert-butylation reactions for the first time. Through a consecutive triple-fluorination process with DBBF and CsF, the (CF3 )3 C- species can be liberated and observed, which is able to serve as a robust nucleophilic perfluoro-tert-butylating agent for various electrophiles. The power of this synthetic protocol is evidenced by the efficient synthesis of structurally diverse perfluoro-tert-butylated molecules. Multiple applications demonstrate the practicability of this method, as well as the superiority of perfluoro-tert-butylated compounds as sensitive probes. The perfluoro-tert-butylated product was successfully applied in 1 H- and 19 F-magnetic resonance imaging (MRI) experiment with an ultra-low field (ULF) MRI system.

A Co(acac)3/PN precatalyst was developed and optimized for catalytic Kumada coupling of aryl Grignard reagents to sterically encumbered alkyl halides. The substrate scope demonstrates excellent yie...

The engagement of unactivated alkyl halides in copper-catalyzed cross-coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper-catalyzed Negishi-type cross-coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon-iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi-type difluoromethylation approach has been applied to the late-stage modification of densely functionalized pharmaceutical agents and natural products.

Herein we report an enantioselective sulfenylation of cyclic imino esters with the efficient and versatile sulfenylation reagent S-alkyl 4-methylbenzenesulfonothioates. By utilizing the Cu/tBu-Phosferrox catalytic system, we can assemble diverse S-alkyl groups into the cyclic imino esters under mild conditions in good yields and with excellent enantioselectivities. Remarkably, this method demonstrates a high tolerance of diverse functional groups and proves to be applicable in the late-stage functionalization of pharmaceuticals.

As one of the most ubiquitous bulk reagents available, the intrinsic chemical inertness of tetrahydrofuran (THF) makes direct and site-selective C(sp 3 )-H bond activation difficult, especially under redox neutral condition. Here, we demonstrate that semiconductor quantum dots (QDs) can activate α-C-H bond of THF via forming QDs/THF conjugates. Under visible light irradiation, the resultant alkoxyalkyl radical directly engages in radical cross-coupling with α-amino radical from amino C-H bonds or radical addition with alkene or phenylacetylene, respectively. In contrast to stoichiometric oxidant or hydrogen atom transfer reagents required in previous studies, the scalable benchtop approach can execute α-C-H bond functionalization of THF only by a QD photocatalyst under redox-neutral condition, thus providing a broad of value added chemicals starting from bulk THFs reagent. The high step- and atom-economy, high efficiency and broad substrate scope make the photocatalysis with QDs and visible light promising in both academic and industrial setting.

Herein, we report the stabilization of nitrene reagents as the source of a nitrogen atom to synthesize nitrogen-incorporated R1 LSi-N←SiLR2 (1) [L=PhC(NtBu)2 ; R1 =NTMS2 , R2 =NTMS]. Compound 1 is synthesized by reacting LSi(I)-SiI L with 3.1 equivalents of Me3 SiN3 at low temperature to afford a triene-like structural framework. Whereas the reaction of the LSi(I)-SiI L with 2.1 equivalents of Me3 SiN3 at room temperature produced silaimine 2 with a central four-membered Si2 N2 ring which is accompanied by a silylene LSi and a cleaved silylene fragment. 1 further reacts with AgOTf at room temperature to yield compound 3 which shows coordination of nitrene to silver with the triflate salt. The compounds 1 and 2 were fully characterized by NMR, mass spectrometry, and X-ray crystallographic analysis. The quantum mechanical calculations reveal that compounds 1 and 2 have dicoordinated monovalent N atoms having two active lone pairs of electrons. These lone pairs are stabilized by hyperconjugative interactions.

Chemical transformation with vinylene carbonate as an emerging synthetic unit has recently attracted considerable attention. This report is a novel conversion pattern with vinylene carbonate, in which such a vibrant reagent unprecedentedly acts as a difunctional coupling partner to complete the C-H annulation of free anilines. From commercially available substrates, this protocol leads to the rapid construction of synthetically versatile 2-methylquinoline derivatives (43 examples) with excellent functionality tolerance.

The efficient and straightforward syntheses of silylthioethers and disulfides are presented. The synthetic methodologies are based on new rhodium complexes containing bulky N-heterocyclic carbene (NHC) ligands that turned out to be efficient catalysts in thiol and thiol–silane coupling reactions. These green protocols, which use easily accessible reagents, allow obtaining compounds containing S–Si and S–S bonds in solvent-free conditions. Additionally, preliminary tests on coupling of mono- and octahydro-substituted spherosilicates with selected thiols have proved to be very promising and showed that these catalytic systems can be used for the synthesis of a novel class of functionalized silsesquioxane derivatives., Two novel rhodium complexes bearing bulky N-heterocyclic carbene ligands have been synthesized and isolated. Both compounds enable efficient and selective formation of silylthioethers and disulfides in solvent-free conditions. A comparison between bulky NHC−rhodium complexes and their smaller derivatives shows that the steric hindrance around the metal center is crucial for effective formation of a product in both catalytic reactions. It has also been proved that the catalysts can be reused several times without loss of activity.

An unprecedented and general hydroboration of alkenes with BX3 (X=Br, Cl) as the boration reagent in the presence of i Pr2 NEt is reported. The addition of i Pr2 NEt not only suppresses alkene polymerization and haloboration side reactions but also provides an "H" source for hydroboration. More importantly, the site-fixed installation of a boryl group at the original position of the internal double bond is readily achieved in contrast to conventional transition-metal-catalyzed hydroboration processes. Further application to the synthesis of 1,n-diborylalkanes (n=3-10) is also demonstrated. Preliminary mechanistic studies reveal a major reaction pathway that involves radical species and operates through a frustrated Lewis pair type single-electron-transfer mechanism.

The asymmetric synthesis of P-stereogenic phosphinates through allylic alkylation of H-phosphinates has been developed. With H-phosphinates and allylic acetates as the starting materials, a variety of allylic P-chiral phosphinates were accessed in high enantioselectivities of up to 92% ee and generally high yields. In addition, a further study demonstrated the applicability of this protocol, including the scale-up synthesis and facile transformation of chiral products from phosphinates to phosphine oxides with organolithium reagents under mild reaction conditions.

α-Aminoalkyl radicals are easily accessible through multiple pathways from various precursors. Apart from their utilization as nitrogen-containing building blocks, they have recently been used as halogen atom abstraction reagents or single-electron reductants to transform organic halides or sulfonium salts into their corresponding highly reactive radical species. Benefiting from the richness of various halides and the diverse reactivity of radical intermediates, new transformations of halides and sulfonium salts have been developed. This short review summarizes this emerging chemistry that uses α-aminoalkyl radicals as the reaction activators.1 Introduction2 Activation of Halides as Halogen-Atom Transfer Agents2.1 Addition to Unsaturated Bonds2.1.1 Addition to C=C Bonds2.1.2 Addition to C=O Bonds2.2 Substitution Reactions2.2.1 Deuteration2.2.2 Olefination2.2.3 Allylation2.2.4 Aromatic Substitution2.2.5 Amination3 Activation of Sulfonium Salts as Single-Electron Reductants4 Conclusion and Outlook

Organophosphonium salts containing C(sp3 )-+ P bonds are among the most utilized reagents in organic synthesis for constructing C-C double bonds. However, their use as C-selective electrophilic groups is rare. Here, we explore an efficient and general transition-metal-free method for sequential chemo- and regioselective C-H and C(sp3 )-+ P bond functionalizations. In the present study, C-H alkylation resulting in the synthesis of benzhydryl triarylphosphonium salts was achieved by one-pot, four-component cross-coupling reactions of simple and commercially available starting materials. The utility of the resulting phosphonium salt building blocks was demonstrated by the chemoselective post-functionalization of benzylic C(sp3 )-+ PPh3 groups to achieve aminations, thiolations, and arylations. In this way, benzhydrylamines, benzhydrylthioethers, and triarylmethanes, structural motifs that are present in many pharmaceuticals and agrochemicals, are readily accessed. These include the synthesis of two anticancer agents from simple materials in only two to three steps. Additionally, a protocol for late-stage functionalization of bioactive drugs has been developed using benzhydrylphosphonium salts. This new approach should provide novel transformations for application in both academic and pharmaceutical research.

A direct C–H halogenation of 3-aryl-1H-pyrazol-5-amines using N-halogenosuccinimides (NXS; X = Br, I, Cl) in dimethyl sulfoxide at room temperature has been developed. This transformation provides an effective metal-free protocol for the synthesis of novel 4-halogenated pyrazole derivatives with moderate to excellent yields. The method utilizes NXS reagents as cheap and safe halogenating reagents under simple and mild reaction conditions, it has broad substrate scope, and can be used for gram-scale synthesis. The utility of this procedure is established by further transformations of the 4-halogenated products. Mechanism studies show that DMSO plays a dual role of catalyst and solvent.

As most of the known systems are flashtype, long-lasting chemiluminescence (CL) emissions are extremely needed for the application of cold light sources, accurate CL quantitative analysis, and biological mapping. In this work, the flashtype system of luminol was altered to a long lasting CL system just because of the paper substrate. The Cu(II)-based organic complex was loaded on the paper surface, which can trigger luminol-H2O2 to produce a long lasting CL emission for over 30 min. By using 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) as the ligand, a hexacoordinated Cu(II)-based organic complex was synthesized by the simple freeze-drying method. It is interesting that the complex morphology can be controlled by adding different amounts of water in the synthesizing procedure. The complex with a certain size can be definitely trapped in the pores of the cellulose. Then, slow diffusion, which can be attributed to the long lasting CL emission, was produced. With the high catalytic activity of the complex, reactive oxygen species from H2O2 was generated and was responsible for the high CL intensity. By using the paper substrate, the flash-type luminol system can be easily transferred to the long-duration CL system without any extra reagent. This long-lasting emission system was used for hydrogen sulfide detection by the CL imaging method. This paper-based sensor has great potential for CL imaging in the clinical field in the future.

Amino-derivatized lignocomposite (ADL-composite) has been designed as an artificial lignin polymer (P1) of monolignol (coniferyl alcohol, CA) enhanced by aniline insertion (P2). The derivatized lignopolymeric (P2) layer covered the surface of a methacrylate particles (SC2/SC6) functionalized previously with amino phenolic crosslinker (p-phenylenediamine (p-Ph-2-NH2) or p-amino-2-hydroxybenzoic acid (p-NH2-SalA)). One-pot biocatalytic approach allowed to combine the preparation of the polymeric materials and also its attachment on the particles surface. Thus, the monolignol (CA) will be oxi-copolymerized together with aniline on the amino pre-functionalized support surface. The oxidation process was performed using H2O2 reagent and catalyzed by peroxidase enzyme (horseradish peroxidase, HRP). The biocatalytic process was evaluated in term of aromatic monomers (CA and aniline) conversion. The chemical structure and properties of the resulted ADL-composites were investigated using specific techniques (e.g. FTIR, TPD, TGA, static contact angle, elemental analysis, and gel permeation chromatography). Attachment of P1/P2 polymer on the particles improved the hydrophobicity and also the basicity of the composite surface. Lipase enzyme was immobilized on the ADL-composites for testing the applicability of ADL-composites for biocatalyst preparation. SEM analysis allowed to notice the modification of ADL-composites surface after enzyme immobilization. Immobilized lipase exhibited better activity compared with free lipase demonstrating the efficiency of ADL-composite as support for enzyme immobilization.

Compared with the well-developed C–C and C–N axial chirality, the asymmetric synthesis of N–N axial chirality remains elusive and challenging. Herein we report the first atroposelective N-acylation reaction of quinazolinone type benzamides with cinnamic anhydrides for the direct catalytic synthesis of optically active atropisomeric quinazolinone derivatives. This reaction features mild conditions and a broad substrate scope and produces N–N axially chiral compounds with high yields and very good enantioselectivities. Besides, the synthetic utility of the protocol was proved by a large scale reaction, transformation of the product and the utilization of the product as an acylation kinetic resolution reagent. Moreover, DFT calculations provide convincing evidence for the interpretation of stereoselection., A highly efficient atroposelective N-acylation reaction of quinazolinone type benzamides with cinnamic anhydrides for the direct catalytic synthesis of optically active atropisomeric quinazolinone derivatives was developed.

It is undoubtedly that constructing heterojunction on the surface of semiconductor materials is an effective way to improve the performance of photocatalysts. Here, Cu2SeI nanospheres were dispersed on the surface of Mn0.05Cd0.95S nanoparticles constructed a p-n heterojunction photocatalyst with high conductivity. Firstly, SEM and TEM showed that the load of Cu2SeI nanospheres successfully formed a close contact on the surface of MCS, which was conducive to the rapid charge transfer between the two. Under visible light irradiation, Na2S/Na2SO3 (0.35 M/0.25 M) was used as sacrifice reagent for hydrogen production. The results showed that the construction of p-n heterojunction was beneficial to charge transfer and the hydrogen evolution ability of the composite catalyst was greatly improve, the 3%MCS/Cu2SeI showed the best hydrogen production activity reaching 677.4 μmol after 5 h, it is 12.3 times higher than that of single catalyst MCS, In addition, the results of X-ray photoelectron spectroscopy (XPS) show that the binding energies of the elements in the composite catalysts are different compared with those in the catalysts alone, indicating that there is a interaction between the catalysts. Through the analysis of photoelectrochemical and fluorescence spectra, the charge transfer kinetics of the composite catalyst was explained and discussed in depth. On the basis of the above analysis results, the possible photocatalytic reaction mechanism of the composite catalyst was proposed, and the mechanism was analyzed and discussed. This work has undoubtedly made a further improvement for the activity of photocatalytic hydrogen production.

Electrosynthesis has received great attention among researchers in both academia and industry as an ideal technique to promote single electron reduction without the use of expensive catalysts. In this work, we report the electrochemical reduction of Katritzky salts to alkyl radicals by sacrificing the easily accessible metal anode. This catalyst and electrolyte free platform has broad applicability to single electron transfer chemistry, including fluoroalkenylation, alkynylation and thiolation. The deaminative functionalization is facilitated by the rapid molecular diffusion across microfluidic channels, demonstrating the practicality that outpaces the conventional electrochemistry setups., Electrochemical transformations use electrons and electron holes instead of chemical oxidants and reductants as reagents. Here, the authors report an electrochemical reductive deaminative cross-coupling of Katrizky salts with various radical acceptors, including examples of fluoroalkenylation, alkynylation and thiolation.

Transamidation reactions are often mediated by reactive substrates in the presence of overstoichiometric activating reagents and/or transition metal catalysts. Here we report the use of CO2 as a traceless catalyst: in the presence of catalytic amounts of CO2, transamidation reactions were accelerated with primary, secondary, and tertiary amide donors. Various amine nucleophiles including amino acid derivatives were tolerated, showcasing the utility of transamidation in peptide modification and polymer degradation (e.g., Nylon-6,6). In particular, N,O-dimethylhydroxyl amides (Weinreb amides) displayed a distinct reactivity in the CO2-catalyzed transamidation versus a N2 atmosphere. Comparative Hammett studies and kinetic analysis were conducted to elucidate the catalytic activation mechanism of molecular CO2, which was supported by DFT calculations. We attributed the positive effect of CO2 in the transamidation reaction to the stabilization of tetrahedral intermediates by covalent binding to the electrophilic CO2.