Highly regioselective nucleopalladation for the oxidative coupling of internal alkynes with alkenyl alcohols by using green and low-costing oxygen as the sole oxidant was investigated. This one-pot cascade cyclization proceeds through Pd-catalyzed intramolecular C–O bond cyclization, insertion of nonbiased alkenyl alcohols, β-H elimination, and reinsertion of a HPdX species, which is finally transferred to the target ketones. This method has the advantages of mild conditions, good functional group tolerance, and can be performed with unactivated alkenes to afford isocoumarin derivatives.

A new type of Lewis acid–base bifunctional M(salphen) complexes (M=Zn^II, Cu^II, and Ni^II) pending two N-methylhomo- piperazine groups as nucleophiles were prepared by a one-pot method. The Zn(salphen) complexes proved to be efficient and recyclable homogeneous catalysts towards the solvent-free synthesis of cyclic carbonates from epoxides and CO₂ in the absence of a co-catalyst. The catalysts can be easily recovered and five times reused without significant loss of activity and selectivity.

A copper(II)-mediated highly selective oxidative cyclization reaction of thioamides to provide 3,5-disubstituted 1,2,4-thiadiazoles was developed. The copper species plays a key role in this transformation and different functional groups are tolerated under the optimal reaction conditions.

A novel strategy involving Cu-catalyzed oxidative transformation of ketone-derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross-coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu-carbene intermediate is proposed for the CC triple bond formation.

Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH₂Cl₂, β-ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and β-ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper-catalyzed NO bond cleavage, activation of a vinyl sp² CH bond, and CS bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives.

A highly efficient and mild palladium-catalyzed, one-pot, four-step cascade annulation has been developed to afford functionalized β- and γ-lactones in moderate to good yields with high regio- and diastereoselectivities in ionic liquids. The employment of ionic liquids under mild reaction conditions makes this transformation green and practical. Especially, this reaction provided a novel and convenient methodology for the construction of naturally occurring biologically active β- and γ-lactones.

Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH₂Cl₂, β-ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and β-ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper-catalyzed NO bond cleavage, activation of a vinyl sp² CH bond, and CS bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives.

A regio- and stereoselective synthesis of sulfones and thioethers by means of Cu^I-catalyzed aerobic oxidative NS bond cleavage of sulfonyl hydrazides, followed by cross-coupling reactions with alkenes and aromatic compounds to form the CS bond, is described herein. N₂ and H₂O are the byproducts of this transformation, thus offering an environmentally benign process with a wide range of potential applications in organic synthesis and medicinal chemistry.

A convenient and highly efficient synthesis of α-methylene-γ-lactones through the palladium(II)-catalyzed lactonization of homoallylic alcohols with alkynamides has been reported. The hydroxyl group in the terminal olefins cooperates with the amide in alkynamides to promote the cyclization by suppressing the β-H elimination. This process provides a route to construct naturally occurring biologically multifunctional α-methylene-γ-lactones.

A novel strategy involving Cu-catalyzed oxidative transformation of ketone-derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross-coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu-carbene intermediate is proposed for the CC triple bond formation.

A practical synthetic method for polysubstituted imidazoles via iodine-catalyzed aerobic oxidative cyclization of aryl ketones and benzylamines has been developed. It was found to tolerate a broad range of substrates to prepare polysubstituted imidazole derivatives in a one-pot manner, and thus importantly allowed product diversity for imidazole chemistry. Additionally, the resultant 1,2,4-trisubstituted imidazoles could be conveniently transformed to functionalized 1,2,4,5-tetrasubstituted imidazoles via electrophilic substitution or direct CH functionalization, or 2,4-diaryl-1H-imidazoles by debenzylation reaction, which further indicates potential applications of this method in synthetic and pharmaceutical chemistry.

A new series of C-6 unsubstituted tetrahydropyrimidines 6 have been directly synthesized via a convenient urea-catalyzed chemoselective five-component reaction (5CR) under mild conditions. Compounds 6 show typical aggregation-induced emission enhancement (AIEE) characteristics because they are practically no emissive in solution but emit blue or green fluorescence in aggregates with fluorescence yield up to 93 %. One of the 5CR products, 6 aa, exhibits blue- and green-fluorescence aggregates (bf- and gf-aggregates). The bf- and gf-aggregates are prepared under different conditions and proved to result from different J-aggregations by single-crystal X-ray analysis. In addition, the bf- and gf-aggregates of 6 aa show unusual size-independent emission (SIE) characteristics because their maximum emission wavelengths in different sizes (suspension particles, film, powder and crystals) are the same, 434 and 484 nm, respectively. Based on the obtained experimental results, the 5CR mechanism, the origins of AIEE and SIE characteristics are discussed.

A palladium-catalyzed, one-pot cyclization reaction to construct (3E)-(imino)isoindolin-1-ones and (3E)-(imino)thiaisoindoline 1,1-dioxides by introducing ortho-reactive functional groups on aryl halides is reported. Under optimal conditions, the cyclization reaction afforded the corresponding products in good to excellent yields (up to 93%) with high stereoselectivity. Notably, this transformation successfully extends its application for the synthesis of phenanthridines and dibenzooxazepines. This new synthetic protocol not only extends the application platform for palladium-catalyzed CC coupling of aryl halides with isocyanides, but also opens atom-economic and step-economic synthetic routes for nitrogen-containing heterocyclic compounds with wide functional group compatibility.

The difunctionalization of terminal alkynes was achieved with silver fluoride (AgF) and N-bromosuccinimide (NBS) as halogen sources. The presence of the halide moiety greatly enhances the reactivity of the vinyl fluoride compounds that can probably can be transformed into various products that are difficult or even impossible to obtain via direct fluorination. Meanwhile, the monofluoro<.>alkenes were facilely synthesized via a highly chemo- and regioselective fluorination of electron-deficient CC triple bonds using AgF as fluorinating reagent in good yields.

The four-component CuI and SnCl₂ co-catalyzed assembly of ketones, amines, alkynes, and carbon dioxide could be performed in DMSO at 70 °C under CO₂ pressure to synthesize 5-alkynlene oxazolidinones. It was found that steric hindrance had an extreme effect on the four-component coupling. Aliphatic ketones, basic primary amines, and aryl alkynes were good substrates.

A series of new isostructural lanthanide MOFs, [Ln₂(pda)₃(H₂O)]·2H₂O [Ln = La (1), Ce(2), Pr(3), Nd(4), Sm(5), Eu(6), Gd(7), Tb(8), Dy(9), Ho(10), Er(11), Tm(12), and Yb(13); H₂dpa = 1,4-phenylenediacetate], have been solvothermally synthesized and structurally characterized by single-crystal (or/and powder) X-ray diffraction analysis. All the MOFs are isostructural and consist of 1D Ln–COO helixes that are cross-linked by the –CH₂C₆H₄CH₂– spacers of the pda^2– anions in a 3D compressed honeycomb-shaped network with 1D open channels, which accommodate guest and coordinated water molecules. Evacuation of [Ln₂(pda)₃(H₂O)]·2H₂O at 200 °C under vacuum generates [Ln₂(pda)₃], which gives X-ray powder diffraction patterns consistent with those of [Ln₂(pda)₃(H₂O)]·2H₂O. MOFs 6 and 8 show characteristic luminescent properties. Activated [Tb₂(pda)₃] exhibits excellent catalytic performance in the heterogeneous acetalization of benzaldehyde with methanol. The possibility for easy recycling makes this catalyst a highly promising candidate to address environmental concerns.

Four new polystyrene-supported amino acids have been synthesized and applied to the chemical fixation of carbon dioxide for the first time. Two series of experiments with polystyrene-supported threonine (PS-Thr) and polystyrene-supported tyrosine (PS-Tyr) as catalyst, respectively, were conducted to study the effect of the reaction conditions on the carboxylation of propylene oxide/carbon dioxide. There was no considerable decrease in the yield of propylene carbonate after the polystyrene-supported amino acids were used five times, indicating that these catalysts are very stable. It was demonstrated that these catalysts were very efficient in the carboxylation of various epoxides and aziridines with carbon dioxide under mild conditions without any solvents. The mechanism for this carboxylation is also discussed.

Transition metal-catalyzed domino reactions have been used as powerful tools for the preparation of polysubstituted furans in a one-pot manner. In this paper, an efficient synthetic method was developed for the construction of tri- or tetrasubstituted furans from electron-deficient alkynes and 2-yn-1-ols by a silver-catalyzed domino reaction. It is especially noteworthy that a 2,3,5-trisubstituted 4-ynyl-furan was formally obtained in an extremely direct manner without tedious stepwise synthesis. In addition, regio-isomeric furans were observed when substituted aryl alkynyl ketones were employed. This methodology represents a highly efficient synthetic route to electron-deficient furans for which catalytic approaches are scarce. The reaction proceeds efficiently under mild conditions with commercially available catalysts and materials.

A palladium-catalyzed alkenylation of 1,2,3-triazoles with terminal conjugated alkenes by direct C–H functionalization has been developed in the presence of Cu(OAc)₂ and dioxygen. A variety of terminal alkenes such as acrylates and styrenes can perform the direct oxidative coupling reactions with 1,2,3-triazoles to afford the corresponding alkenylated products in 30–90 % yield.

A facile method for the synthesis of trisubstituted allenynes has been developed. The process involves phosphane-mediated deoxygenation of 2,4-pentadiyn-1-ol derivatives. A variety of propargyl alcohols can be transformed into allenynes in moderate to good yields under mild reaction conditions.

Condensation of maleic anhydride or dimethyl maleate with benzylaldehydes controlled by tris(4-anisyl)-phosphine to synthesize dimethyl (E)-2-benzylidenesuccinates has been systematically investigated. The protocol gives the product with high stereoselectivity in moderate to good yields under mild conditions. A plausible mechanism has been proposed.

With some common metal salts (CuI, FeCl₃) as catalysts, alkynes can be effectively electrocarboxylated with CO₂ (4 MPa) in an undivided cell with Ni cathode and Al sacrificial anode containing n-Bu₄NBr-DMF as supporting electrolyte with a constant current at room temperature. The saturated tricarboxylic acids besides the dicarboxylic acids were obtained in good yields. The yields of the tricarboxylic acids were strongly influenced by various metal salt catalysts, cathode materials and the property of substituted groups. Finally, the possible electrochemical mechanism was discussed.

The formation of carbon–carbon and carbon–oxygen bonds continues to be an active and challenging field of chemical research. Nanoparticle catalysis has attracted considerable attention owing to its environmentally benign and high activity toward the reactions. Herein, we described a novel and effective nano-Cu₂O-catalyzed one-pot domino process for the regioselective synthesis of α-carbonyl furans. Various electron-deficient alkynes with 2-yn-1-ols underwent this process smoothly in moderate to good yields in the presence of air at atmospheric pressure. It is especially noteworthy that a novel 2,4,5-trisubstituted 3-ynylfuran was formed in an extremely direct manner without tedious stepwise synthesis. Additionally, as all of the starting materials are readily available, this method may allow the synthesis of more complex α-carbonyl furans. An experiment to elucidate the mechanism suggested that the process involved a carbene intermediate.

A green, simple and effective polymer-supported catalytic system has been developed for the cyclization of propargyl alcohols with carbon dioxide (CO₂). α-Alkylidene cyclic carbonates were obtained in satisfactory isolated yields in most cases. The catalyst could be recovered by simple filtration and reused several times without significant loss of activity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A novel and convenient one-pot synthesis of polyfunctional tetrahydropyrimidine analogues through a Lewis acid catalyzed multicomponent reaction is disclosed. This domino reaction proceeds smoothly in moderate-to-good yields with formation of four C–N bonds in one step. The products are interesting nitrogen heterocycles that contain α- and β-amino acid blocks. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A safe, environmentally friendly and cost-effective method for the synthesis of β-amino acid derivatives has been developed. Treatment of α,β-unsaturated compounds with aliphatic amines furnishes β-amino acid derivatives in good to excellent yields via a catalyst- and solvent-free aza-Michael addition.

Using amino acid hydrochloride salt as a catalyst, the coupling reaction of CO₂ with epoxides could proceed smoothly to give cyclic carbonates in very good yields and high selectivity. The reaction conditions such as the pressure of carbon dioxide, reaction temperature, time and catalyst loading were carefully investigated.

An eco-friendly and cheap Zn-H₂O-CO₂ system was presented for chemoselective reduction of nitrobenzenes to anilines with high yields (80% –97% isolated yields) in supercritical carbon dioxide. This process brings together the very important green chemistry technologies–the use of carbon dioxide as a solvent and the use of water as a hydrogen donor.

Based on the reactive behaviour of the substrates, two synthetic routes to polysubstituted pyrimidine derivatives are presented herein: 1) A catalyst-free multicomponent reaction of electron-deficient alkynes, aliphatic amines and formaldehyde and 2) Ag^I-catalyzed synthesis of pyrimidines from electron-deficient alkynes, anilines and formaldehyde by a domino reaction. Under optimized conditions, the multicomponent reactions were accomplished with high regioselectivity and excellent yields. A computational study was carried out by using the B3LYP density functional theory to elucidate the mechanisms of the catalyst-free hydroamination reaction. Calculations showed the activation free energies of aliphatic amines were lower than those of anilines, which is consistent with the experimental results.