Chiral tertiary alcohols are ubiquitous in medicinally relevant agents and biologically active natural products. Although some catalytic asymmetric approaches for the synthesis of chiral tertiary alcohols have been reported, the development of efficient methods for enantioselective construction of tertiary alcohols is still highly appealing. Most recently, we have developed Pd-catalyzed asymmetric decarboxylative cycloaddition of vinylethylene carbonates (VECs) with formaldehyde to construct tertiary alcohol derivatives. The reaction was catalyzed by the chiral palladium complex with a chiral phosphoramidite to afford methylene acetal protected tertiary vinylglycols in high efficiency. Since the pioneer works by Gong and Takemoto respectively for the allylic substitution under cooperative catalysis of palladium complex and chiral phase-transfer catalyst, the asymmetric allylic substitution synergistically catalyzed by transition metal and organocatalyst has recently attracted a great deal of attention. However, there have been no reports on the combination of transition-metal and squaramide for the allylic alkylation. In this communication, we will report the asymmetric decarboxylative cycloaddition of VECs with formaldehyde under cooperative catalytic system of achiral palladium complex and chiral squaramide. With combination of palladium complex in situ generated from Pd₂(dba)₃·CHCl₃ (2.5 mol%) and achiral phosphine ligand L4 (10 mol%) and chiral squaramide OC2 (25 mol%) as cooperative catalysts, the reaction of VECs with paraformaldehyde (10 equiv.) proceeded smoothly to give desired tertiary alcohol derivatives in good yields (51%~65%) with moderate enantioselectivities (62%~79% ee). The reaction conditions are also suitable for the reaction of VEC with electronic deficient arylaldehydes to afford desired products in high yields with good enantioselectivities, although the catalytic system is less effective for the control of the diastereoselectivities. Although the enantioselectivity of the reaction is not significantly high, we firstly demonstrated that the chiral induction for the cycloaddition reaction could be achieved under the cooperative catalytic system of achiral palladium complex and chiral squaramide. The detail reaction mechanism and stereochemical outcome are currently underway, and will be reported in due course.

Enantioenriched pyrrolidines bearing a β-aryl group and an α-quaternary carbon stereocenter are important structural motifs in many natural products and pharmaceuticals, and their enantioselective synthesis has thus received extensive attention over the last several decades. Nonetheless, so far as we know, asymmetric aminoarylation of alkenes to access such targets has only been independently reported by Wolfe and Liu using palladium catalysis involving a key aminopalladation step, and thus, general and practical methodologies towards a variety of chiral pyrrolidines are still in demand and highly desirable. As part of our ongoing interest in radical-initiated difunctionalization reactions of alkenes based on Cu(I)/chiral phosphoric acid (CPA) catalysis, we sought to develop a mechanistically distinct and complementary approach for this asymmetric palladium(Ⅱ)-catalyzed aminoarylation of alkenes. Herein we describe our efforts toward the development of the efficient asymmetric radical-initiated aminoarylation of alkenes with aryldiazonium salts enabled by Cu(I)/CPA catalysis. A general procedure for the aminoarylation of alkenes with aryldiazonium salts is as follows:under argon, an oven-dried resealable Schlenk tube equipped with a magnetic stir bar was charged with urea substrate 1 (0.1 mmol, 1.0 equiv.), CuI (1.9 mg, 0.01 mmol, 10 mol%), CPA[(S)-A1 (9.3 mg, 0.015 mmol, 15 mol%], aryldiazonium salts 2 (0.12 mmol, 1.2 equiv.), Na₃PO₄ (19.7 mg, 0.12 mmol, 1.2 equiv.) and isopropyl acetate(1.0 mL) at 32℃ and the sealed tube was then stirred under the same conditions. Upon completion (monitored by thin-layer chromatography), the reaction mixture was directly purified by silica gel chromatography[eluent:V(petroleum ether):V(EtOAc)=100:0 to 3:1] to afford the desired product 3. The enantiometric excess of product was determined by chiral high-performance liquid chromatography (HPLC) analysis. A broad scope of substrates worked well under this standard conditions to afford enantioenriched pyrrolidines in good yield with good to excellent enantioselectivity. A series of control experiments were conducted to determine the reaction mechanism as a radical process and a possible mechanism was proposed.

A pharmaceutical intermediate, 3-pyridyl benzoxazole derivatives (DIHY), was designed and synthesized as the guest molecule. The self-assembly binding models of tetramethyl cucurbit[6] uril (TMeQ[6]), cucurbit[7] uril (Q[7]) and cucurbit[8] uril (Q[8]) with DIHY were investigated by ¹H NMR, MS, isothermal titration calorimetry and UV-Vis spectrum. The results showed that there are different modes of interaction between these three different cucurbit[n] uril and DIHY. For the TMeQ[6]-DIHY system, the guest molecule is located at the port of the TMeQ[6], while for the Q[7]-DIHY system, the 4,5-dihydro-2H-benzoxazole moiety of the guest molecule reside within the cavity of Q[7] host, whereas the pyridyl group of DIHY guest remains outside of the portal to form the 1:1 inclusion complexes of pseudorotaxane structure. Nevertheless, the 4,5-dihydro-2H-benzoxazole moiety of two guest molecule is included in the cavity of Q[8] host in a "face to face" stacking way, while the pyridine group of DIHY is located at the port of Q[8] to form a 1:2 supramolecular structure.

Sulfonamide is a key structural unit of several groups of vitally synthetic drugs that have been extensively used as antimicrobials, antiretroviral drugs and anticancer agents. In particular, enantiomerically pure sulfonamides represent a rapidly-increasing important substance in new drug discovery due to their unique pharmacological properties. Thus, developing asymmetric synthetic methods involving rapid and highly efficient construction of these compounds is extremely important and highly demanded for medicinal chemists. In our laboratory, we have reported a serial of asymmetric multicomponent reactions via trapping reactive ammonium ylides generated from amines and diazo compounds in the presence of transition metal complexes and chiral phosphoric acids. In this work, an asymmetric three-component reaction of sulfonamides, diazo compounds and imines cooperatively catalyzed by Rh₂(OAc)₄ and chiral phosphoric acids was reported. This Rh₂(OAc)₄ and chiral phosphoric acids cooperatively catalyzed three-component reaction of sulfonamides, diazo compounds and imines accomplished with satisfying yields (up to 85%), high diastereoselectivity (>20:1) and excellent enantioselectivity (up to 99% ee), thus providing a rapid access to synthesize enantiomerically enriched sulfonamides bearing two adjacent chiral carbons. Furthermore, this newly developed three-component reaction was carried out on a gram-scale with a lower catalyst loading and without impacting the yield, diastereoselectivity and enantioselectivity. Finally, we explored the further transformation of obtained three-component reaction products:1) treatment of 5aaa with LiAlH₄ under 0℃ in THF for 8.0 h gave the corresponding alcohol derivative 6 in 82% yield without changing the diastereoselectivity and enantioselectivity (0.20 mmol scale); 2) treatment of 5aaa with triphosgene and triethylamine under 0℃ in DCM for 1.0 h, gave five-membered heterocyclic sulfoximine derivative 7 bearing three adjacent chiral atoms (2 carbons and 1 sulfur) in 80% yield with perfect diastereoselectivity (>20:1) and remained enantioselectivity (0.20 mmol scale).

Recent developments in the field of asymmetric α-functionalization of arylacetic acids and derivatives by combining chiral Lewis base and transition-metal catalyst are summarized. The unique character of Lewis bases, specifically, chiral benzotetramisole derivatives, plays a crucial role in these innovative strategies.

The combination of N-heterocyclic carbenes (NHCs) and Lewis acids (LA) have been occasionally employed in asymmetric annulation reactions. However, synergistic effect of LA on NHC-mediated reactions remains scarce. Herein, we demonstrate that by switching LA co-catalysts, two distinct active species, homoenolate and acyl azolium, can be accessed from the same set of substrates. NHC-catalyzed enantioselective hydroesterification is one of the most straightforward strategies to prepare β-chiral esters. Despite recent advances for this redox-neutral transformation, obtaining high enantioselectivity and yield remains challenging. We recently reported synergistic catalysis, combining an achiral NHC and a chiral phosphoric acid, enables highly enantioselective hydrothioesterification and hydroesterification of enals. However, both stereoselectivity and yield for hydroesterification are far from ideal. Specifically, sluggish reactions, accompanied with ee's in mid-80% are often obtained. Additionally, competing pathways for E/Z isomerization and oxidative esterification of enal are serious for a number of substrates. In order to address this issue, we propose a new cooperative catalytic system, consisting of a NHC, a LA and a proton-shuttling agent, might accelerate the pivotal asymmetric β-protonation process. We suspect that the choice of LA might provide complementary reaction pathways from the same enal substrates. Starting from β-alkyl cinnamaldehydes, highly enantioselective hydroesterification is accomplished via asymmetric β-protonation enabled by a magnesium co-catalyst. In sharp contrast, the same homoenolate intermediate can undergo aerobic oxidation, via single electron transfer (SET), in the presence of a ruthenium co-catalyst. Control experiments show distinct rate difference between the E-and Z-isomers of enal. Substrates with Z-configuration react significantly slower under the standard reactions. E/Z isomerization is also slow. Photoirradiation was applied to address the challenging issue of isomeric enals and both high yield and ee are obtained using start materials as E/Z mixtures. General procedure for the asymmetric β-protonation is as following:NHC pre-catalyst (0.01 mmol), MgCl₂ (0.01 mmol), DABCO (0.12 mmol), 4 ? MS (100 mg), alcohol (0.6 mmol) and enal substrate (0.1 mmol) were dissolved in toluene (1.0 mL). The resulted mixture was stirred at room temperature under Ar atmosphere for 15 h. Upon complete consumption of the enal, the mixture was concentrated and purified by flash column chromatography. For the aerobic oxidation, the reaction proceeded with RuCl₃ (0.01 mmol) under O₂ atmosphere.

Allylic alkylation first pioneered by Tsuji in 1965 and, later adapted by Trost in 1973 with the introduction of phosphine ligands represents one of the straightforward and powerful synthetic tool for new carbon-carbon formation, especially the direct asymmetric allylic alkylation (AAA) has been widely utilized in the synthesis of natural products and pharmaceutical molecules. Conventionally, AAA reactions involve activated allylic alcohol derivatives, such as carbonates, amines, acetates, and halides, which require an equivalent strong base to react with the acidic by-product and inevitably results in stoichiometric waste. From the viewpoint of environmental and atom economy, the direct use of allylic alcohol instead its derivatives is much more practical by virtue of only water being formed as a byproduct. However, one of the challenges existed in such transformations is the poor reactivity of allylic alcohol. In 2006, a breakthrough was first made by Trost group, by using stoichiometric amounts of borane as the critical promoter in the direct AAA reaction of indoles with allylic alcohols. Afterwards, List, Gong, and Zhang reported independently the significant achievements applying aldehyde, pyrazol-5-ones, and ketones as nucleophiles, respectively. In 2004, our group enclosed the Brønsted acid accelerated Pd-catalyzed direct asymmetric allylic alkylation of azlactones with simple allylic alcohols. On the other hand, triphenylamine (TPA) as a strong electron-donating and oxidative stable molecule has been extensively utilized in the new organic electroluminescent materials, special dye synthesis and organic solar cells. Considering the impressive fluorescence emission ability of TPA and basing on these pioneering works, we reasoned that the direct connection of the TPA substructure with amino acid molecules could give rise to the fluorescence emission compounds. Thus, we report here the first installation of the non-natural amino acid derivatives bearing TPA core skeleton via Pd-catalyzed direct AAA reaction and the desired products were obtained with excellent yields (68%~95%) and enantioselectivities (90%~97% ee). The optimized reaction condition is as following:To a dried Schlenk tube were added activated 5 Å MS (100 mg), Pd₂(dba)₃ (4.0 mol%), L3 (10.0 mol%), solvent toluene (1.0 mL), and was stirred at 60℃ for 20 min. Then the reaction mixture was cooled down to room temperature, azlactones 1 (0.2 mmol), allylic alcohol 2 (0.3 mmol) and benzoic acid (10.0 mol%) in toluene (1.0 mL) was added and continue to stir at 60℃ for 20 h until the reaction was complete (monitored by TLC). The solvent was then removed under vacuum and the residue was purified by flash chromatography on silica gel to afford the desired product.

Transition-metal-catalyzed asymmetric insertion of carbene into O-H bonds is a straightforward method for the synthesis of chiral alcohols and their derivatives. In recent years, a variety of chiral catalysts have been developed to achieve high enantioselective insertions of metal carbenes derived from α-diazoesters into O-H bonds of alcohols, phenols, carboxylic acids, and even water. However, there are few successful examples of the asymmetric O-H bond insertion using α-diazoketones as carbene precursors. In this paper, we report the first asymmetric O-H insertion of α-diazoketones with alcohols co-catalyzed by achiral dirhodium complexes and chiral spiro phosphoric acids. The reaction has high yields and high enantioselectivity (up to 95% ee). The present O-H bond insertion reaction provides an efficient method for the synthesis of very useful chiral α-alkoxy ketones, which are easily transformed to corresponding 1,2-diol derivatives with excellent diastereoselectivity. The density functional theory (DFT) calculation was performed to study the mechanism of the reaction. It is found that the chiral spiro phosphoric acid can promote the proton transfer process of enol intermediates generated from rhodium carbene and alcohol like chiral proton-transfer shuttle and realize enantioselectivity control accordingly. Water are likely to participate in this proton transfer step and has a remarkable effect on the enantiocontrol of the reaction. A typical procedure for the enantioselective O-H bond insertion of α-diazoketones is as follows. Powered Rh₂(TPA)₄ (2.9 mg, 0.002 mmol, 1 mol%) and chiral spiro phosphoric acid (R)-1k (3.3 mg, 0.004 mmol, 2 mol%) were introduced into an oven-dried Schlenk tube in an argon-filled glovebox. After CHCl₃ (2 mL) was injected into the Schlenk tube, the solution was stirred at 25℃ under the argon atmosphere. A solution of benzyl alcohol (21.6 mg, 0.2 mmol) and 1-diazo-1-phenylpropan-2-one (2a, 33.8 mg, 0.21 mmol) in 1 mL of CHCl₃ were then introduced into the Schlenk tube containing catalysts. The resulting mixture was stirred at 25℃ until the diazo compound 2a disappeared. After concentration in vacuo, the residue was purified by flash chromatography on silica gel (petroleum ether/ethyl acetate, V:V=15:1) to give (-)-1-(benzyloxy)-1-phenyl-propan-2-one (4a, 43.2 mg, 0.18 mmol, 90% yield) as a colorless oil.

Transition metal catalysis is one of the most important tools to accurately forge chemical bonds in modern organic synthesis. Organocatalysis, a biomimetic catalysis usually with metal-free small organic molecules, is a relatively young research area that started to flourish at the beginning of this century. Catalytic allylic substitutions are a kind of versatile reactions in organic chemistry; the combination of transition metal catalysis and organocatalysis in these reactions not only significantly expands the scope of nucleophiles, but also helps to resolve the stereocontrol issues. This paper will summarize the advance in the field of catalytic asymmetric allylic substitutions through synergetic transition metal-and organocatalysis. According to the source of chirality, these advances will be classified to three types. The first type is the catalytic asymmetric allylic substitutions induced by chiral transition metal catalysts. For these reactions, chiral ligands, including phosphine ligands and hybrid P, N ligands, have been used to achieve the high enantioselectivity. The non-chiral organocatalysts, such as pyrrolidine, Brønsted acids and boron reagents, were only used to activate the nucleophile or assist the generation of π-allyl metal intermediates. The second type is the catalytic asymmetric allylic substitutions induced by chiral organocatalysts. For the reaction of this type, various chiral organocatalysts, including chiral amines, chiral ureas and others, not only activate the substrates, but also control the enantioselectivity of allylic substitutions well through covalent and non-covalent bonds. Non-chiral ligands were only used to improve the catalytic capacity of transition metals. The last type is the catalytic asymmetric allylic substitutions induced by both of chiral transition metal catalysts and chiral organocatalyst. This strategy can not only realize the excellent stereo-control, but also achieve the challenging diastereo-diversity, if there exist continuous chiral centers. Overall, the joint utilization of transition metals and organocatalysts can achieve many significant asymmetric allylic substitutions that were previously difficult to realize through single transition metal catalysis. Meanwhile, the mechanism of representative transformations will be briefly introduced and at last, the prospective in this area will be given, such as simpler allylic sources and greener catalyst system.

Compared with indium(Ⅲ), indium(I) has both vacant p-orbitals and an electron lone pair, showing distinctive catalytic behaviors. However, chiral indium(I) catalysis has been rarely reported. Previously, we have developed asymmetric binary acid catalysis with indium(Ⅲ) and chiral phosphoric acid for a number of enantioselective transformations. Asymmetric binary-acid catalysis in[4+2] cycloaddition of β,γ-unsaturated α-keto esters with different olefins have been reported by our groups over the past five years. In 2013, we developed exo-selective and enantioselective[4+2] cycloaddition of simple industrial feedstock olefins, such as propene and isobutene, styrene and so on, catalyzed by In(BArF)₃/1a. However, the reaction with electron-rich olefins, such as 4-methoxylstyrene did not work very well by indium(Ⅲ) catalysis due to uncontrolled polymerization side pathway. Very recently, we developed a new binary acid system InCl/1a, which could catalyze enantioselective[4+2] annulation of β,γ-unsaturated α-keto esters with much more electron-rich alkoxyallenes. In this study, we reported that the binary acid InCl and 1a was an effective and exo-selective catalyst for the[4+2] cycloaddition of simple olefins. In the presence of InCl (10 mol%) and chiral phosphoric acid 1a (10 mol%), the reaction occurred smoothly to afford the desired cycloadducts in moderate to good yields (20%~93%), with excellent diastereoselectivity (>95:5, exo/endo) and enantioselectivity (up to 99% ee) under the room temperature in CHCl₃. Different olefins, such as styrenes 2, ring-strained norbornene 5a, norbornadiene 5b, and cyclopentadiene dimer 5c all worked well with excellent stereoselectivity under the optimal reaction conditions. More importantly, when 4-methoxylstyrene is used, the reaction can proceeded smoothly to afford[4+2] adduct 4k in 70% yield and good stereoselectivity (>95:5 dr, and 88% ee). The typical procedure for asymmetric[4+2] cycloaddition is as follows:To a dry reaction tube was added chiral phosphoric acid 1a (0.005 mmol, 5 mol%), InCl (0.005 mmol, 5 mol%), 4 Å MS (10 mg), 3 (0.1 mmol), then CHCl₃ (0.5 mL) and 2 or 5 (0.5 mmol) was added to the mixture. The mixture was stirred for 24 h at room temperature. The mixture was purified by column chromatography to give the desired cycloaddition products 4 or 6.

L-Cys-β-CD@AuNPs nanoparticles were synthesized by a simple method of the reduction of HAuCl₄ with NaBH₄and L-Cys-CD. The catalytic activity of L-Cys-β-CD@AuNPs nanoparticles for the catalytic reductions of 4-nitrophenol and 4-nitro-1-naphthol was researched in detail. Because of the selective binding of β-cyclodextrin (β-CD) to different guest molecules, L-Cys-β-CD@AuNPs exhibits diverse catalytic activities for different substrates. The experimental results prove that L-Cys-β-CD@AuNPs shows better catalytic efficiency for the reduction of 4-nitro-1-naphthol than p-nitrophenol.

Pyropheophorbide-a methyl ester and its derivatives acidylated and alkenylated along the N²¹-N²³ axis were used as starting materials. The 1,3-dipolar cyclocaddition, Michael addition and Tiffeneau-Demjanov rearrangement reaction can smoothly occur with diazoalkane through the carbon-oxygen or carbon-carbon double bonds attached to the periphery to generate new heterocyclic and carbonylic structures in different positions. The synthesis of a series of unreported chlorins related to chlorophyll was accomplished and their chemical structures were characterized by elemental analysis, UV-Vis, IR, MS and ¹H NMR spectra. Meanwhile, the region-and stereo-selectivities of rearrangement processes were discussed based on relevant reaction mechanism.

In the presence of copper acetate, ten 5-(1-phenyl-3-phenylprop-2-ynyl)-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives were synthesized via the three component one-pot reaction of aldehydes with 2,2-dimethyl-1,3-dioxane-4,6-dione and phenylacetylene by using Na-ascorbate as a reductant. The reaction has the advantages of high yields (65%~86%), mild conditions, simple operation and environmental friendliness. It provides an effective method for the synthesis of 5-(1-phenyl-3-phenylprop-2-ynyl)-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives.

Heterocyclic compounds are not only important intermediates in organic synthesis and medicine synthesis, but also the basic building framework of biologically active natural products. In recent years, Pd-catalyzed C(sp³)-H bonds activation has been demonstrated as one of the hot topics in the field of heterocyclic compound synthesis because of its high atomic economic characteristics. Herein, the recent research progress in the construction of heterocyclic compounds via Pd-catalyzed C(sp³)-H bond activation is summarized according to the classification of the ring number of heterocyclic compounds (mainly including N, O heterocycles). The reaction selectivity, substrate compatibility, reaction mechanism, advantages and disadvantages as well as an outlook in this field are also discussed.

Ketones are ubiquitous chemical entries in natural products, biologically active molecules, and functional materials. As such, developing operationally simple and general methods for the synthesis of these scaffolds is highly desiable. Recently, oxidative radical addition to aldehydes has emerged as a highly efficient strategy for the direct access of ketones. The strategy features a formal 1,2-hydrogen atom transfer of resulting alkoxy radicals, followed by single electron transfer oxidation and deprotonation to give various cyclic or acyclic ketones in promising yields with a broad substrate scope. Recent advances in this area, including both intramolecular and intermolecular versions, are discussed herein.

Pyrrolo[1,2-a] quinoxalines are a kind of important nitrogen-containing heterocycles which are widely existed in the natural products and bio-active molecules. Therefore, the synthesis of such motifs, especially those with substituted pyrrolo[1,2-a] quinoxalines, is of great significance in theory and reality. This review focuses on the research process towards the synthesis of pyrrolo[1,2-a] quinoxalines and 4,5-dihydropyrrolo[1,2-a] quinoxalines, including the advantages and disadvantages as well as an outlook in this field.

Isobenzofuranone derivatives are widely found in nature and have shown diverse biological activities. In this work, the aniline-promoted synthesis of isobenzofuranone derivatives starting from 2-carboxybenzaldehyde and substituted acetophenones under mild reaction conditions is reported. This method has broad substrate scope, high yields, and is operationally convenient, and therefore could serve as an attractive strategy for practical synthesis of isobenzofuranone derivatives.

We report an asymmetric tandem reaction realized by sequential Au(I)/chiral bifunctional tertiary amine catalysis. A tandem olefination/asymmetric cyclization reaction is developed, allowing facile synthesis of quaternary spirocyclic oxindoles in good yields and stereoselectivities from N-Ac protected diazooxindoles 1, monofluorinated enol silyl ethers 2 and 2-tosylaminochalcone 4. The initial cross coupling reaction of diazooxindole and fluorinated enol silyl ethers, catalyzed by 3.0 mol% IPrAuBF₄, readily afforded 3-alkenyloxindoles for the subsequent Michael/Michael addition of 2-tosylaminochalcone catalyzed by 5.0~10.0 mol% chiral bifunctional tertiary amine-squaramide C1. The tandem reaction was performed by the following general procedure. Under an atmosphere of N₂, to an oven-dried Schlenk tube were added IPrAuCl (6.0 mg, 0.0099 mmol, 3.3 mol%) and AgBF₄ (1.8 mg, 0.0090 mmol, 3.0 mol%), followed by anhydrous CH₂Cl₂ (1.0 mL). The resulting mixture was stirred at 25℃ for 0.5 h and then cooled down to 0℃. After ethers 2 (1.5 equiv.) was added in one-portion, a solution of diazooxindoles 1 in 1.5 mL of CH₂Cl₂ was added slowly by a syringe pump in 20 minutes. The reaction was stirred at 0℃ till full consumption of 1 by TLC analysis. After the successive addition of C1 and 4 (1.1 equiv.), the reaction was warmed to 25℃ and stirred till full consumption of 3, and the mixture was directly subjected to the column chromatography by using petroleum ether/dichloromethane (1/2.5, V/V) as the eluent to give the desired spirocyclic oxindoles 5. The diastereoselectivities of 5 (>20:1) were determined by ¹H NMR analysis of the crude reaction mixture. The key step of this tandem sequence is the cross coupling reaction of monofluorinated enol silyl ethers and donor-acceptor diazo reagents. We further examined the substrates scope of acyclic aryl diazoacetates and fluorinated enol silyl ethers by using 1.0 mol% IPrAuSbF₆ as catalyst, providing a new method for the efficient synthesis of trisubstituted alkenes.

Recently, N-heterocyclic carbene (NHC) catalysis has achieved significant achievement in the field of cooperative catalysis. With the combination of other established catalysis modes (e.g., Lewis acid, Brønsted acid/base, hydrogen-bond donor), great improvement has been made in the enhancement of reactivity and stereoselectivity, and this strategy has emerged as a powerful instrument in organic synthesis to construct complex molecules. However, owing to the strong propensity of NHCs to bind to transition metals, the development of cooperative catalysis of NHCs and transition metals remains a longstanding and challenging work. At present, some important progress has been made in the combination of NHCs with palladium, copper and ruthenium, and the coordination of NHCs and transition metals can be controlled by the modulation of ligand and alkalinity in reaction system, which not only avoiding the deactivation of the catalysts, but also improving the reaction activity efficiently. This strategy has also been used in the asymmetric construction of bioactive molecular scaffolds. In this perspective, the achievements on NHC and transition metals cooperative catalysis will be discussed.

In the recent decade, the palladium-catalyzed allylic C-H alkylation reaction of simple alkenes has been well-established as an efficient and atom-economical synthetic alternative for the fine chemical synthesis without the requirement of any prefunctionalization, in comparison with the conventional procedures. We recently established a highly enantioselective α-allylation reaction of enolizable aldehydes with terminal alkenes by using a ternary catalyst system, including palladium, amine, and chiral Brønsted acid, wherein the chiral anion controls the enantioselectivity. Although this protocol provides allylic alkylation products with high levels of enantioselectivity of up to 90% ee, the extension of the optimal conditions to a 1,4-diene led to a very low regioslectivity. In the presence of a palladium complex, an oxidant and a chiral phosphoric acid, the 1,4-diene could be smoothly oxidized and principally generated two regiomeric π-vinylallyl-palladium phosphate intermediates, either of which led to different products. Therefore, the simultaneous control of regio-and stereoselectivities in the allylic C-H alkylation reaction of aldehydes with 1,4-dienes would pose additional challenge in comparison with a similar reaction of allylarenes. Herein, we will report an asymmetric α-allylation of enolizable aldehydes with a wide range of 1,4-dienes enabled by cooperative catalysis of a palladium complex, amine, and a chiral Brønsted acid. The presence of 6 mol% Pd(OAc)₂, 24 mol% P(4-MeOC₆H₄)₃, 6 mol% chiral phosphoric acid (R)-TRIP, 80 mol% cumylamine and 1.50 equivalents of 2,6-dimethylbenzoquinone enabled (E)-penta-1,4-dien-1-ylbenzene (1a) to smoothly undergo the asymmetric allylic C-H alkylation reaction with 2-phenylpropanal (2a), giving rise to the desired α-allylated aldehyde 3a in a 77% isolated yield, 11:1 regioselectivity, 20:1 E/Z and 93% ee. Under the optimal conditions, the generality for enolizable aldehydes was investigated and revealed that 2-aryl propinonaldehydes bearing either electron-donating or electron-withdrawing substituent at the para-(3b~3f) or meta-(3g~3i) position of the phenyl moiety were nicely tolerated, giving rise to the desired allylation products in moderate to good yields with excellent regio-, E/Z-and enantioselectivities. Moreover, 2-naphthyl propinonaldehyde was also able to participate in the asymmetric allylic C-H alkylation reaction, providing the allylation product (3j) with 73% yield, 10:1 regioselectivity, 12:1 E/Z and 91% ee. The examination of 1,4-dienes found that this protocol tolerated a wide scope of aryl and alkyl substituted 1,4-dienes, which showed broad adaptability for the facile construction of a broad spectrum of chiral α-quaternary carbonyl compounds. In addition to the terminal aryl-substituted 1,4-dienes (3k~3q), different substitution patterns were allowed to offer excellent enantioselectivities ranging from 92% ee to 95% ee. Interestingly, this protocol was also amenable to a long chain aliphatic substituent. Although a terminal phenyl (3r) group showed detrimental effect on the regio-and E/Z-selectivities, while the ester (3s), chloride (3t), ether (3u) and cyclohexyl (3v) groups were nicely compatible with the protocol, affording the products with satisfactory results in terms of yields, regio-and stereoselectivities.

An efficient method for carbon-carbon bond formation via desulfurative coupling of pyrimidine thioethers/4-phenylquinoline thioethers with alkynes or arylboronic acids is described. The reaction was promoted by a cheap and stable copper salt[copper(I) acetate] and catalyzed by palladium with good yields and wild substrate scope.

In this study, a controlled synthesis of hyper-crosslinked monodisperse microsphere with homogeneous mesoporous aperture about 6 nm is presented. After supported with palladium, the catalyst was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption and desorption surface area analyses. The results showed that HCP-(PS-DVB)-Pd(0) possessed high catalytic activity for Suzuki-Miyaura cross-coupling reaction at room temperature, and the catalyst also show excellent reusability. After recycled for 10 times, the yield can maintain above 95% and the surface areas can still reach 480.5 m²·g^-1. These results suggest that the HCP-(PS-DVB)-Pd(0) catalyst has potential applications in synthetic and industrial chemistry.

A novel carbazole-based Schiff base derivative L was synthesized and evaluated for the property of selective detection of HSO₄^- ion in aqueous medium. N-(9-Ethyl-carbazol-3-yl)-1-methyl-1-(4-nitrophenyl)-methanimine (L) selectively recognized HSO₄^- ion in CH₃CN-H₂O (V:V=9:1) via the hydrolysis reaction of Schiff bases to elicit a distinct visual colour change from orange to colorless with a significant blue fluorescence under the UV lamp. The fluorescence enhancement phenomenon caused by HSO₄^- ion did not change in the presence of other anions. The sensing mechanism of probe L for HSO₄^- had been investigated by Job's plot, ¹H NMR titration spectra and HRMS spectrum. The detection limit for the HSO₄^- ion was determined as 1.91×10^-8mol·L^-1. The compound L can be used as a highly selective and sensitive colorimetric, and fluorescent turn-on probe for HSO₄^-.

Transition-metal-catalyzed decarboxylative cross-coupling reactions have been well developed as efficient synthetic methods in organic synthesis. Herein the new application of silver-catalyzed decarboxylation in Hunsdiecker-type halogenation, carbon-carbon bond formation, carbon-heteratom bond formation and C-H bond functionalization reaction is discussed. The recent progress in silver-catalyzed decarboxylative coupling reaction with aliphatic carboxylic acids, α-keto acids and aryl carboxylic acid is reviewed. With the assistance of peroxides, selective decarboxylative coupling reaction could be proceeded via free-radical process by silver catalysis. The controlled free-radical transformation is operational simplification without the exclusion of water and oxygen under mild conditions.

A series of natural product-like terphenyls were synthesized, and their biological activities were evaluated. 4"-Amino-[1,1':4',1"-terphenyl]-3,4-diol (17) has the most potent cytotoxic activity against the MDA-MB-435 cell line, and the IC₅₀ value is (0.20±1.12) μmol/L, which is more potent than compounds X1 and X2 obtained in our previous studies. DNA relaxation test showed that compound 17 had a strong inhibitory effect on topoisomerase Ⅱα (TOP2α), but not on topoisomerase I (TOP1), which was consistent with the docking analysis results. Our studies demonstrate that N contained substitutes on ring C are important for producing terphenyls with more efficacious activity against TOP2α, which provide insight into the development of novel terphenyl topoisomerase Ⅱα inhibitors.

Oxime organic dyes, acting as photoredox catalysts, are widely used in visible-light-induced organic synthesis due to their advantages of low cost, good water solubility, high reactivity and so on. The type of organic dyes-catalyzed organic reactions is continuously expanding, and there is a tendency that organic dyes are gradually replacing some of transition metal catalysts. Classified by the type of reactions, the research progress of several common organic dyes in visible-light-induced organic synthesis in recent years is reviewed, and their future outlook is also discussed.