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Phosphine catalysis generally relies on the potential of carbanion-phosphonium zwitterions that are generated via nucleophilic addition of phosphine catalyst to electrophilic reactants. Consequently, structural modification of zwitterions using distinct electrophilic reactants has emerged as a prominent strategy to enhance catalysis diversity. Herein, we present an alternative strategy that utilizes AgF additive to expand phosphine catalysis. We find that AgF can readily transform the canonical carbanion-phosphonium zwitterion into silver enolate-fluorophosphorane intermediate, eventually furnishing a P(III)/P(V) catalytic cycle. This strategy has been successfully applied to the phosphine-catalyzed reaction of 2-substituted allenoate and imine, resulting in the transition from Kwon [4 + 2] cycloaddition to [3 + 2] cycloaddition. This [3 + 2] cycloaddition features remarkable diastereoselectivity, high yield, and broad substrate scope. Experimental and computational studies have validated the proposed mechanism. Given the prevalence of carbanion-phosphonium zwitterions in phosphine catalysis, this AgF-assisted strategy is believed to hold significant potential for advancing P(III)/P(V) catalysis., (© 2024. The Author(s).)

The insertion of carbonyl into C(sp 2 )-Pd(II) σ-bond (Grignard-type addition) was not established until the 1990s. While this elemental reaction has been well explored since then, its application in Pd(0) asymmetric catalysis remain elusive. Herein, we report the Pd(0)-catalyzed asymmetric intramolecular Grignard-type reaction of vinyl iodide-carbonyl in the presence of HCO 2 H additive, affording cyclic allylic alcohol with good to excellent enantioselectivity and diastereoselectivity. Mechanistic studies suggested that besides serving as an efficient reductant, HCO 2 H is also capable of facilitating protonation of the involved secondary alkoxyl-Pd(II), thus completely suppressing the β-H elimination. Moreover, no KIE was found in the competing reaction between vinyl iodide-aldehyde and 1-deuterated one, demonstrating the facile step of aldehyde insertion., (© 2024 Wiley-VCH GmbH.)

The Heck/Suzuki tandem reaction has emerged as an essential strategy for the synthesis of complex molecules. Herein, an efficient palladium-catalyzed Heck/Suzuki tandem reaction of ( Z )-1-iodo-1,6-dienes with organoboronic acids is described, providing various tetrahydropyridines in good to excellent yields under mild reaction conditions. The key to the success of this approach is the avoidance of the intramolecular second Heck insertion occurring prior to the transmetalation step. In addition, the asymmetric version of this reaction is investigated to deliver chiral tetrahydropyridine in excellent yield with promising enantioselectivity.

A ligand-free Pd(0)-catalyzed cyclization of (Z)-5-iodo-4-pentenenitrile has been realized with the help of HCO 2 H reductant, which is followed by imine hydrolysis to afford cyclopentenone derivatives in moderate to good yields. Control experiments clearly points out that the proton originally came from HCO 2 H plays a crucial role on protonation of the resultant imido-Pd 2+ intermediate. This protocol features mild condition, operational simplicity, as well as wide functional group tolerance.

Although nanoengineering of electrodes opens up the way to the development of solid oxide fuel cells (SOFCs) with improved performance, the practical implementation of such advances in cells suitable for widespread use remains a challenge. Here, the demonstration of large-area, commercially relevant SOFCs with two nanoengineered electrodes that display excellent performance is reported. The self-assembled nanocomposite La 0.6 Sr 0.4 CoO 3- δ and Co 3 O 4 is strategically designed and deposited into the well-interconnected Ce 0.9 Gd 0.1 O 2- δ backbone as a cathode to enable an ultra-large electrochemically active region. The nanometer-scale Ce 0.8 Gd 0.2 O 2- δ is deposited into a conventional Ni/yttria-stabilized zirconia (YSZ) anode to provide more active oxygen exchange kinetics and electronic conductivity compared to YSZ. The resulting nanoengineered cell with an effective size of 4 cm × 4 cm delivers a remarkable power output of 19.2 W per single cell at 0.6 V and 750 °C. These advancements have potential to facilitate the future development of high-performance SOFCs at a large scale by nanoengineering of electrodes and are expected to pave the way for the commercialization of this technology.

In this study, starch-polyphenol complexes (CES-TPS complexes) were prepared using various ratios (0%, 2%, 4%, 6%, 8%, and 10%, based on starch) of tea polyphenols (TPS) and high amylose corn starch (HACS) pretreated with starch branching enzyme (SBE). It was aimed to determine the effects of TPS on the physicochemical and structural properties and digestibility of the CES-TPS complexes. Scanning electron microscopy and laser particle size analysis showed that the addition of a moderate amount of TPS will reinforce interaction force, while excessive TPS will cause a loose structural morphology, leading to an increase in starch particle size. Thermal property analysis indicated that SBE pre-treatment decreased T O , T P and T C of HACS, and the gelatinization temperature was further reduced after adding TPS. The digestion of CES-TPS complexes was investigated using an Artificial Gut analyzer; the predicted glycemic index of starch samples decreased with the addition of a low concentration of TPS (2-6%), while there was a significant increment in the pGI of starch samples when a high concentration of TPS (8-10%) was added. XRD analysis showed that the relative crystallinity of the CES-TPS complexes further increased to 21.91% and then decreased to 19.38% with the increase of TPS concentration. The ratios of 1047/1022 cm -1 presented the opposite trend to that determined by FT-IR.

Although the Heck reactions of alkene partners with various electrophiles have achieved great success, the variant focused on carbon═heteroatom counterparts still remains elusive. Herein, we report a Pd(0)-catalyzed asymmetric intramolecular hydrazone-type Heck reaction of N -[( Z )-3-iodoallyl]-aminoacetaldehyde and hydrazine hydrate (NH 2 NH 2 -H 2 O), wherein the required hydrazone is in situ generated via an acid-promoted condensation. A key strategic advantage of this Heck paradigm is that the resultant Heck product allylic diazene rapidly undergoes stereospecific denitrogenative [1,5]-sigmatropic rearrangement, eventually furnishing a domino sequence toward 3-substituted tetrahydropyridine (THP) with high enantioselectivity. The substrate-induced diastereoselective version has also been realized, exclusively giving cis -2,5-disubstituted THPs. The utility of this sequence is demonstrated by the formal synthesis of multiple valuable bioactive targets, including 3-ethylindoloquinolizine, preclamol, and niraparib.

Despite diversity in reaction mechanisms, the palladium-catalyzed cyclization of 1,6-enyne generally proceeds in a 5- exo manner. Herein, we report the development of a Pd(0)-catalyzed hydroacyloxylative cyclization of 1,6-enyne in either 7- endo -trig or 6- exo -trig fashion when paired with an appropriate dihaloacetic acid reactant, such as F 2 HCCO 2 H and Cl 2 HCCO 2 H. Using the combination of Pd 2 (dba) 3 and a chiral phosphine ligand, the hydroacyloxylative cyclization of 1,6-enyne bearing a 1,1-disubstituted alkene moiety readily gives highly enantiopure seven-membered heterocycles while the reaction of those having a 1,2-disubstituted alkene affords six-membered rings with moderate enantioselectivity. Preliminary experimental studies suggest a reaction mechanism featuring an unusual E -to- Z vinyl-Pd(II) isomerization and alkene trans-oxypalladation, which is proven to be governed by the rationally selected carboxylate.

Reductive elimination of alkyl-Pd II -O is a synthetically useful yet underdeveloped elementary reaction. Here we report that the combination of an H-bonding donor [PyH][BF 4 ] and AgNO 3 additive under toluene/H 2 O biphasic system can enable such elementary step to form alkyl nitrate. This results in the Pd 0 -catalyzed asymmetric carbonitratations of (Z)-1-iodo-1,6-dienes with (R)-BINAP as the chiral ligand, affording alkyl nitrates up to 96 % ee. Mechanistic studies disclose that the reaction consists of oxidative addition of Pd 0 catalyst to vinyl iodide, anion ligand exchange between I - and NO 3 - , alkene insertion and S N 2-type alkyl-Pd II -ONO 2 reductive elimination. Evidences suggest that H-bonding interaction of PyH⋅⋅⋅ONO 2 can facilitate dissociation of O 2 NO - ligand from the alkyl-Pd II -ONO 2 species, thus enabling the challenging alkyl-Pd II -ONO 2 reductive elimination to be feasible., (© 2022 Wiley-VCH GmbH.)

The coronavirus disease 2019 (COVID-19), which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread over the world, resulting in a global severe pneumonia pandemic. Both the cell receptor angiotensin-converting enzyme 2 (ACE2) and the breakdown of S protein by transmembrane serine protease 2 (TMPRSS2) are required by SARS-CoV-2 to enter the host cells. Similarly, the expression level of viral receptor genes in various organs determines the likelihood of viral infection. Several animal species have been found to be infected by the SARS-CoV-2, such as minks, posing an enormous threat to humans. Because the mice and rats were closely related to human and the fact that rats and mice have a risk of infection by SARS-CoV-2 with specific variants, we investigated the expression patterns of 79 receptor genes from 107 viruses, including SARS-CoV-2, in 14 organs of the rat and mouse, and 5 organs of the muskrat, to find the most likely host organs to become infected with certain viruses. The findings of this study are anticipated to aid in prevention of zoonotic infections spread by rats, mice, muskrats, and other rodents.

Whereas the intramolecular reductive Heck reaction of aryl/vinyl halide and alkene has been well documented, the oxime analogue remains extremely elusive. Herein we report the Pd(0)-catalyzed intramolecular reductive Heck reaction of vinyl iodide and oxime ether with the use of formic acid as the reductant. It is found that the TsOH additive plays a crucial role in the reaction efficiency, and the ( S )-SEGPhos ligand enables cyclic allylic N -alkoxy amine products with high enantioselectivity.

A MnO2-promoted oxidative coupling process between N,N-disubstituted hydrazine and boronic ester is reported. A 1,1-diazene species is firstly generated upon oxidation of a hydrazine substrate in the presence of MnO2 which then interacts with boronic ester to form the key intermediate boron-ate complex, followed by migration from boron to nitrogen to form a new C-N bond. This new finding provides mild, scalable, and operationally straightforward access to trisubstituted hydrazine.

The dihalogenative cyclization of 1,6-enyne with the assistance of PhI(OAc) 2 and lithium halide is presented. A plausible radical mechanism is proposed, which consists of addition of halogen radical to alkene, 5-exo-dig radical cyclization of enyne and halogenation via radical coupling. The alkenyl- and alkyl-halide groups in the resulted pyrrolidine products have been demonstrated to be facile handles for further transformations.

Carbon-halogen reductive elimination is a conceptually novel elementary reaction. Its emergence broadens the horizons of transition-metal catalysis and provides new access to organohalides of versatile synthetic value. However, as the reverse process of facile oxidative addition of Pd(0) to organohalide, carbon-halogen reductive elimination remains elusive and practically difficult. Overcoming the thermodynamic disfavor inherent to such an elementary reaction is frustrated by the high reaction temperature and requirement of distinctive ligands. Here, we report a general strategy that employs [Et 3 NH] + [BF 4 ] - as an H-bond donor under a toluene/water/(CH 2 OH) 2 biphasic system to efficiently promote C(sp 3 )-halogen reductive elimination at low temperature. This enables a series of Pd(0)-catalyzed carbohalogenation reactions, including more challenging and unprecedented asymmetric carbobromination with a high level of efficiency and enantioselectivity by using readily available ligands. Mechanistic studies suggest that [Et 3 NH] + [BF 4 ] - can facilitate the heterolytic dissociation of halogen-Pd II C(sp 3 ) bonds via a potential H-bonding interaction to reduce the energy barrier of C(sp 3 )-halogen reductive elimination, thereby rendering it feasible in an S N 2 manner.

Osteoporosis is a common chronic disease in the elderly population and in some domestic animals. Caged layer osteoporosis (CLO) is a common bone metabolism disease that was recently recommended as an ideal animal model for osteoporosis. This study aimed to investigate the therapeutic effect and mechanism of dietary icariin (ICA), the main bioactive component of the Chinese herb Epimedium, on low bone mineral density (BMD) in older caged laying hens. A total of 216, 54-week-old Lohmann pink-shell laying hens were allocated to three groups, comprising one control group and two treatment groups that were additionally supplied with 0.5 or 2.0 g kg-1 ICA. The results showed that dietary ICA significantly increased the femur BMD by 49.3% and the tibia BMD by 38.9%, improved the microstructure of bone tissue, decreased levels of the bone metabolism index, enhanced serum antioxidant capacity and regulated messenger RNA expression of bone-related genes. ICA-induced differential metabolites were clarified by using untargeted metabolomics assays. Furthermore, correlation analysis between differential metabolites and BMD indicated that eight differential metabolites correlated highly with both femur and tibia BMD, including uridine, taurine, palmitic acid, adrenic acid, fexofenadine, lysoPC(18 : 1), lysoPE(20 : 3/0 : 0) and 3-acetyl-11-keto-beta-boswellic acid. ICA mainly perturbed pyrimidine metabolism, taurine metabolism and lipid metabolism, which led to increased BMD in older caged laying hens. These findings revealed underlying therapeutic mechanisms of dietary ICA on low BMD, and provided reference metabolites for the early diagnosis of osteoporosis.

A Pd(0)-catalyzed cyclizative carboboration reaction of n -iodo-1,6-diene ( n = 1, 2) with B 2 pin 2 has been developed. When 1-iodo-1,6-diene was employed as the substrate, a process of intramolecular 6,6-alkenylboration was achieved to deliver 6-membered cyclic allylborate. On the other hand, 2-iodo-1,6-diene was found to proceed via 2-cyclopropanation/1-boration, thus affording a (bicyclo[3.1.0]hexan-1-ylmethyl)borate product.

Despite various advantages of high-temperature solid oxide electrolysis cells (SOECs) over their low-temperature competitors, the insufficient long-term durability has prevented the commercialization of SOECs. Here, we address this challenge by employing two nanoengineered electrodes. The O 2 electrode consists of a La 0.6 Sr 0.4 CoO 3-δ (LSC) and Gd,Pr-co-doped CeO 2 (CGPO) nanocomposite coating deposited on a Gd-doped CeO 2 (CGO) scaffold, and the H 2 electrode comprises a Ni/yttria stabilized zirconia (YSZ) electrode modified with a nanogranular CGO coating. The resulting cell with an active area of 4 × 4 cm 2 exhibits a current density exceeding 1.2 A cm -2 at 1.3 V and 750 °C for steam electrolysis while also offering excellent long-term durability at 1 A cm -2 with a high steam-to-hydrogen conversion of ∼56%. We further unravel the degradation mechanism of the most commonly used Ni/YSZ electrode under these conditions and describe the mitigation of the discussed mechanism on our nanoengineered electrode. Our findings demonstrate the potential of designing robust SOECs by nanoengineering electrodes through infiltration and have significant implications for the practical integration of SOEC technology in the future sustainable energy system.

A palladium-catalyzed cyclizative phosphorylation reaction of (Z)-1-iodo-1,6-diene with diethyl H-phosphonate is developed, which provides facile access to unsaturated six-membered heterocycles bearing an alkylphosphonate group. The key step of this process is the efficient capture of the involved alkyl-Pd(II) species by H-phosphonate with the help of CsF, followed by reductive elimination of alkyl-Pd(II)-P(O)(OEt) 2 . Moreover, this reaction is successfully extended to H-thionophosphonate.

A Pd(II)-catalyzed intramolecular and highly selective acetxoylative (3 + 2) annulation of propargylic alcohol and alkene is reported. Mechanistically, a hydroxy-guided regioselective alkyne acetoxypalladation is followed by 6-exo-trig alkene insertion to form an alkyl-Pd(II) intermediate. After oxidation, the resulting cyclometalated alkoxy-Pd(IV)-alkyl undergoes direct reductive elimination to afford a polycyclic oxa-heterocycle. When an additional coordinating site or ligand accessible by palladium is present, an S N 2-type C-C reductive elimination of alkyl-Pd(IV) instead occurs along with hydroxy acetylation, affording 3-bicyclo[4.1.0]heptan-5-one products.

The palladium-catalyzed electrochemical C-H bromination of benzamide derivatives under divided cells is developed, in which NH 4 Br serves as a brominating reagent and electrolyte. The protocol avoids the use of chemical oxidants and provides an alternative method for the synthesis of aryl bromides.

The substrate-dependent annulations of δ-acetoxy allenoates with α-hydroxy-β-carbonyl ester derivatives are reported. 2-[(Methoxycarbonyl)oxy]malonate as a C1 partner is able to undergo (1 + 4) annulations with allenoates in the presence of a catalytic amount of phosphine, affording cyclopentadienes in good yields. However, (2 + 4) annulations of allenoates with 2-(tosyloxy)-3-ketoesters are instead observed with the assistance of stoichiometrical phosphine and base, leading to tetrasubstituted benzene products. In these two reactions, δ-acetoxy allenoate serves as a 1,4-disubstituted diene synthon.

Conventional Ni/yttria-stabilized zirconia (YSZ) electrodes in solid oxide cells experience fast degradation when operated for the electrolysis of steam at high current densities. This study presents a relatively simple procedure of infiltrating Ce0.8Gd0.2O2-δ (CGO) nanoparticles into the Ni/YSZ electrode to achieve a stable cell performance. The long-term durability tests of the cells with a bare Ni/YSZ electrode and a CGO-infiltrated Ni/YSZ electrode were performed at 800 °C and -1.25 A cm-2. The cell stability was investigated by measuring the cell voltage and obtaining the electro-chemical impedance spectra. The post-mortem analysis of the tested cells was conducted via scanning and transmission electron microscopy. The CGO nanoparticle infiltration reduced the cell voltage degradation rate from 699 mV kh-1 for the bare Ni/YSZ electrode to 66 mV kh-1 for the infiltrated electrode. The investigation showed that after introducing CGO nanoparticles, the steam reduction mechanism changed, and the electrode degradation originated from different mechanisms than that for the bare Ni/YSZ electrode.

A mild and efficient synthetic protocol for 3-pyrrolines via the phosphine-catalyzed (3 + 2) annulation of δ-acetoxy allenoates with 2-sulfonamidomalonate is reported. The asymmetric version (up to 83% ee) is also achieved by using phosphine ( R)-SITCP as the catalyst. Mechanistic experiments disclose that the involved deprotonation of amide N-H and aza-addition to vinyl phosphonium might proceed in a concerted manner.

The first example of phosphine-catalyzed α-umpolung addition of nucleophiles to allenoates is described, which features the use of δ-acetoxy allenoate to generate a 3-phosphonium-2,4-dienoate intermediate, thus facilitating the α-umpolung addition of nucleophiles. Both sulfinate and diarylphosphine oxide are competitive nucleophiles, affording highly activated conjugated dienes with good to excellent stereoselectivities.

Phosphine-catalyzed (3+2) annulations of δ-acetoxy allenoates with 2-naphthols are reported, wherein the δC of allentoate reacts with the αC of 2-naphthol to form the C-C bond while a C-O bond is formed between the γC of allenoate and the hydroxyl group of 2-naphthol. When (R)-SITCP is used as the catalyst, 1,2-dihydronaphtho[2,1-b]furans are obtained in moderate to good yields and with high enantioselectivity. This method is useful for the construction of enantiomerically enriched atropoisomeric furans via a central to axial chirality conversion strategy.

A general iron-catalyzed strategy for the atom-transfer radical cyclization (ATRC) of allylic halide is reported. Critical to this strategy is the use of DPPF [1,1'-bis(diphenylphosphino)ferrocene] as catalyst, which allows for efficient generation of the allylic radical species via a single-electron transfer (SET) process. The feasibility of achieving ATRC reactions of propargyl chlorides is also demonstrated, which affords products with an exocyclic allene moiety.

The phosphine-catalyzed substrate-dependent (4 + 2) annulations of δ-acetoxy allenoates with ketones is described. Allenoates 1 with an alkyl substituent at δC are able to react with cyclic 1,3-diketones 2, wherein the δC is attacked by the methenyl carbon of 2 while the αC attacks the ketone of 2. Allenoates 5 with an aryl group at δC is poised to react with cyclic β-carbonyl amides 6, in which the αC is attacked by the methenyl carbon of 6 and the δC undergoes 1,2-addition to the ketone of 6.

While the phosphine catalysis is a powerful tool for the construction of N-heterocycles, the phosphine-catalyzed annulations toward lactam motif are still extremely scarce. Here, we report the asymmetric (3 + 2) annulations of δ-acetoxy allenoates with β-carbonyl amides by using the (R)-SITCP catalyst. The δC and γC of allenoate respectively engage in annulation with the αC and N of the amide, forging a γ-lactam with good to excellent stereoselectivity.

A Pd(0)/(S)-p-MeO-BnPHOX catalytic system has been established for the asymmetric reductive Heck reaction of (Z)-1-iodo-1,6-dienes, which affords quaternary tetrahydropyridines with good to excellent enantioselectivities. This reaction tolerates a wide range of substituted alkene moieties, including 1,1-disubstituted, 1,1,2-trisubstituted as well as 1,2-disubstituted alkenes.

Here is reported the DMAP-catalyzed addition/(4 + 2) annulation domino reaction of δ-acetoxy allenoate with either salicylaldehyde-derived oxadiene or pyrrolealdehyde-derived oxadiene, which provides a facile method toward polycyclic frameworks. A cationic intermediate, 3-ammonium-2,4-dienoate, is proposed to be involved via an addition-elimination process between an allenoate and a catalyst, which is capable of undergoing addition with either O- or N-nucleophile and subsequent (4 + 2) annulation with oxadiene.

The formal (3 + 3) annulations of δ-acetoxy allenoates and 1C,3O-bisnucleophiles are reported with the use of 6'-deoxy-6'-perfluorobenzamido-quinine (4g) as a catalyst, which provide rapid access to 4H-pyrans with excellent enantioselectivity. The reaction features a wide reaction scope and mild reaction conditions. The crucial roles of amide NH of 4g as a H-bond donor have also been elucidated, which not only activates allenoate to facilitate formation of cationic intermediate A but also enhances the electrophilicity of its δ-position for nucleophilic 1,6-addition.

Celastrol, isolated from the traditional Chinese medicinal herb Tripterygium wilfordii Hook. f. (Thunder God's Vine), has been used to treat cancer, chronic inflammatory, autoimmune and other human diseases. However, to date, the protein targets and the mechanism of action of celastrol have remained elusive. In this study, we find that celastrol can react with protein thiols in a unique covalent and reversible manner, while protein denaturing disrupts the interaction. Through a competitive chemoproteomics approach utilizing a cysteine-targeting activity-based probe, we report the proteome-wide quantitative profiling of cellular targets of celastrol in human cervical cancer HeLa cells. Representative targets are further validated via in vitro binding experiments and/or enzymatic activity assays. Bioinformatics analysis results suggest that celastrol exerts its numerous therapeutic effects through interaction with promiscuous proteins involved in various biological processes and cellular pathways.

The asymmetric (3 + 3) annulations of β'-acetoxy allenoates with either 3-oxo-nitriles or pyrazolones have been realized by using 6'-deoxy-6'-[(l)-N,N-(2,2'-oxidiethyl)-valine amido]quinine (6h) as the catalyst. The three functions of catalyst 6h, including Lewis base (quinuclidine N), H-bond donor (amide NH), and Brønsted base (morpholine N), cooperatively take crucial roles on the chemo- and enantioselectivity, allowing for the construction of 4H-pyran and 4H-pyrano[2,3-c]pyrazole in high yields and enantioselectivity.

The π-acid-catalyzed cyclizations of 1,n-enynes by carbophilic activation have been extensively studied and appear as highly attractive processes, yet the cases within a catalytic cycle based on redox principle are rare. Herein, we report the cyclizative addition reactions of 1,6-enynes and sulfonyl chlorides by using a [Rh(cod)Cl/dppf] (dppf=1,1'-bis(diphenylphosphino)ferrocene) catalyst system. The process features the involvement of oxidative addition of sulfonyl chloride to Rh(I) catalyst, which generates [(dppf)(RSO2 )RhCl2 ] as a π-acid species to trigger cyclizative addition in a 6-endo-dig manner by carbophilic activation. Moreover, the catalytic protocol is also applicable to 1,6-diene analogues., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A rhodium(III)-catalyzed cascade cyclization/electrophilic amidation using N-pivaloyloxylamides as the electrophilic nitrogen source has been developed. This protocol provides an efficient route for the synthesis of 3-amidoindoles and 3-amidofurans under mild conditions with good functional group tolerance. The synthetic utility of this reaction has been demonstrated through the derivatization of the 3-amidoindoles to several heterocycle-fused indoles.

The amine-catalyzed cascade (3 + 2) annulation and aromatization sequence between β'-acetoxy allenoates and 1,2-bisnucleophiles has been developed. When 1,4-dithane-2,5-diol is used as the bisnucleophile partner, the corresponding reaction affords fully substituted thiophene-2-carbaldehyde, which might proceed via the amine-catalyzed (3 + 2) annulation and subsequent oxidative aromatization. The reaction protocol is also applicable to a 2-tosylamino-carbonyl bisnucleophile, wherein the (3 + 2) annulation is followed by 1,2-elimination of a tosyl group and isomerization to give a 1H-pyrrole product.

N-Alkoxyacrylamides are coupled with N-phenoxyacetamides by Rh(III) catalysis through C-H functionalization and amido group transfer under external oxidant-free conditions, which affords acyclic alkene carboamination products in an atom-economical way. Mechanistic insight into this transformation indicates the amide group in N-alkoxyacrylamide plays a critical role in this C-C/C-N bond formation reaction. This methodology provides a highly efficient way to construct o-tyrosine derivatives under mild conditions.

In this paper, a reagent-controlled [3+2] annulation of γ-functionalized butynoates 1 and 1C,3O-bisnucleophiles 2 is reported, which leads to three distinct furan skeletons 3-5. A PPh(3) catalyst preferentially attached the β-position of 1a, facilitating α-addition to furnish Type I annulations. With the assistance of Ag(2)O, Type II annulations were achieved via selective γ-substitution. In the absence of the PPh(3) catalyst, the reagent Cs(2)CO(3) promoted β-addition to realize Type III annulations., (© 2011 American Chemical Society)

A RhCl(PPh(3))(3)-catalyzed halogen-exchange reaction between allyl and alkyl halides with β-H atoms was observed. The possible mechanism of the reaction involves oxidative addition and reductive elimination of the C(sp(3))-X bonds, which is not common in organometallic chemistry.

A new PPh(3)-catalyzed synthesis of alkyl 2-[aryl(tosylimino)methyl]acrylates from propiolate and N-tosylimine has been developed. Deuterium-labelling experiments show that the reaction mechanism involves several hydrogen-transfer processes, which are not the turnover-limiting step and strongly rely on the nature of the reaction media. The stable phosphonium-enamine zwitterion, which was proven to play an important role in the catalytic cycle, has been isolated and characterised by X-ray analysis.

A palldium(0)-catalyzed tandem cyclization/Suzuki coupling reaction of various 1,6-enyne substrates was developed. This Pd-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined alpha-arylmethylene-gamma-butyrolactones, lactams, multifunctional tetrahydrofurans, pyrrolidines, and cyclopentanes. The mechanism of the reaction was studied by the employment of different enyne isomers and boronic acids; a pi-allyl palladium intermediate was suggested to explain the formation of the cyclic products. The stereochemistry of this reaction can be well explained by a chairlike transition state.

The palladium-catalyzed tandem reactions of yne-propargylic carbonates with aryl boronic acids, 2-furyl boronic acid, and 2-thiopheneboronic acid, followed by 6pi-electrocyclization to give fused ring aromatic products such as naphthalene, benzofuran, and benzothiophene derivatives are realized. Screening of the reaction conditions revealed that the combination of [Pd(PPh3)4] in THF gave the best results in terms of reactivity and product yields in the reaction of yne-propargylic carbonates with phenylboronic acid. The reaction is sensitive toward steric hindrance when substituted phenylboronic acids are employed. However, when we take 2-furyl boronic acid as the organometallic reagent, most substrates perform very well to give benzofuran derivatives. In addition, 2-thiopheneboronic acid is also a very effective coupling reagent to give bezothiophenes in high yields. A mechanism is proposed that involves the formation of an allenylpalladium complex from Pd0 and propargylic carbonate, followed by insertion of an intramolecular triple bond and the Suzuki coupling reaction, and then electrocyclization.

A new Rh-catalyzed 1,6-enyne cycloisomerization process with a pi-allyl rhodium species as the key intermediate is investigated. A halogen shift happened in this novel process. The synthesis of stereodefined alpha-halomethylene gamma-butyrolactones has been achieved using the readily accessible Rh catalysts.