Nickel: The “Spirited Horse” of Transition Metal Catalysis

A Nickel(II)-Mediated Thiocarbonylation Strategy for Carbon Isotope Labeling of Aliphatic Carboxamides

A series of pharmaceutically relevant small molecules and biopharmaceuticals bearing aliphatic carboxamides have been successfully labeled with carbon-13. Key to the success of this novel carbon isotope labeling technique is the observation that ¹³ C-labeled Ni^II -acyl complexes, formed from a ¹³ CO insertion step with Ni^II -alkyl intermediates, rapidly react in less than one minute with 2,2'-dipyridyl disulfide to quantitatively form the corresponding 2-pyridyl thioesters. Either the use of ¹³ C-SilaCOgen or ¹³ C-COgen allows for the stoichiometric addition of isotopically labeled carbon monoxide. Subsequent one-pot acylation of a series of structurally diverse amines provides the desired ¹³ C-labeled carboxamides in good yields. A single electron transfer pathway is proposed between the Ni^II -acyl complexes and the disulfide providing a reactive Ni^III -acyl sulfide intermediate, which rapidly undergoes reductive elimination to the desired thioester. By further optimization of the reaction parameters, reaction times down to only 11 min were identified, opening up the possibility of exploring this chemistry for carbon-11 isotope labeling. Finally, this isotope labeling strategy could be adapted to the synthesis of ¹³ C-labeled liraglutide and insulin degludec, representing two antidiabetic drugs.

Nickel-Fe3O4 Magnetic Nanoparticles Supported on Multiwalled Carbon Nanotubes: Effective Catalyst in Suzuki Cross Coupling Reactions

Nickel-Fe3O4 nanoparticles supported on multi-walled carbon nanotubes (Ni-Fe3O4/MWCNTs) were synthesized by mechanical grinding of a sample of nickel salt, Fe3O4 and MWCNTs using a ball-mill mixer. The preparation method allows for bulk production of Ni-Fe3O4 nanoparticles at room temperature without the necessity of any solvent or chemical reagent. The nanoparticles prepared by this method exhibit small particles size of 5–8 nm with uniform dispersion of nickel nanoparticles on the surface of multi-walled carbon nanotubes. The Ni-Fe3O4/MWCNTs demonstrated remarkable catalytic activity for Suzuki cross coupling reactions of functionalized aryl halides and phenylboronic acids with excellent turnover number and turnover frequency (e.g., 76,000 h−1) using Monowave 50 conventional heating reactor at 120 °C within a very short reaction time of 15 min. The catalyst is air-stable and exhibits easy removal from the reaction mixture due to its magnetic properties, recyclability with no loss of activity, and significantly better performance than the other well-known commercial nickel catalyst. The Ni-Fe3O4/MWCNTs nanoparticles were fully characterized by a variety of spectroscopic techniques including X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Since nickel offers similar properties to other more expensive transition metals including the most widely used palladium counterpart in cross coupling catalysis, this work demonstrates a promising lower-cost, air-moisture stable and efficient alternative catalyst based on nickel nanoparticles for cross coupling reactions.

Organosolv Fractionation of Walnut Shell Biomass to Isolate Lignocellulosic Components for Chemical Upgrading of Lignin to Aromatics

Renewable carbon sources are a rapidly growing field of research because of the finite supply of fossil carbon. The lignocellulosic biomass walnut shell (WS) is an attractive renewable feedstock because it has a high lignin content (38-44 wt %) and is an agricultural waste stream. Lignin, a major component of lignocellulosic biomass that is currently a waste stream in pulping processes, has unique potential for chemical upgrading because its subunits are aromatic. In the interest of improving the sustainability and reducing the environmental impact of biomass processing, valorization of agricultural waste streams is important. Herein, three lab-scale, batch organosolv procedures are explored in the interest of optimal isolation of protected WS lignin (WSL). One system uses acetic acid, one MeOH, and the final EtOH as the primary solvent. The optimal condition for protected WSL isolation, which resulted in a 64% yield, was methanol and dilute sulfuric acid with formaldehyde to act as a protecting group at 170 °C. Select samples were upgraded by hydrogenolysis over a nickel catalyst. Protected lignin recovered from the optimal condition showed 77% by weight conversion to monomeric phenols, demonstrating that the protected WSL can selectively afford high value products. One key finding from this study was that MeOH is a superior solvent for isolating WSL versus EtOH because the latter exhibited lignin recondensation. The second was that the Ni/C-catalyzed reductive catalytic fractionation (RCF) directly of WS biomass was not selective relative to RCF of isolated WSL; conversion of raw WS to monomers produced significantly more side products.

Zero-valent ML2 complexes of group 10 metals supported by terphenyl phosphanes

Bulky terphenyl phosphane ligands PMe₂Ar' (Ar' = terphenyl group) facilitate the isolation of zero-valent bis-phosphane complexes of nickel, palladium and platinum. The former show coordination numbers greater than two in the solid state due to the existence of Ni-C_arene interactions with the terphenyl fragment.

BIAN-NHC Ligands in Transition-Metal-Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N-Heterocyclic Carbenes?

The discovery of NHCs (NHC = N-heterocyclic carbenes) as ancillary ligands in transition-metal-catalysis ranks as one of the most important developments in synthesis and catalysis. It is now well-recognized that the strong σ-donating properties of NHCs along with the ease of scaffold modification and a steric shielding of the N-wingtip substituents around the metal center enable dramatic improvements in catalytic processes, including the discovery of reactions that are not possible using other ancillary ligands. In this context, although the classical NHCs based on imidazolylidene and imidazolinylidene ring systems are now well-established, recently tremendous progress has been made in the development and catalytic applications of BIAN-NHC (BIAN = bis(imino)acenaphthene) class of ligands. The enhanced reactivity of BIAN-NHCs is a direct result of the combination of electronic and steric properties that collectively allow for a major expansion of the scope of catalytic processes that can be accomplished using NHCs. BIAN-NHC ligands take advantage of (1) the stronger σ-donation, (2) lower lying LUMO orbitals, (3) the presence of an extended π-system, (4) the rigid backbone that pushes the N-wingtip substituents closer to the metal center by buttressing effect, thus resulting in a significantly improved control of the catalytic center and enhanced air-stability of BIAN-NHC-metal complexes at low oxidation state. Acenaphthoquinone as a precursor enables facile scaffold modification, including for the first time the high yielding synthesis of unsymmetrical NHCs with unique catalytic properties. Overall, this results in a highly attractive, easily accessible class of ligands that bring major advances and emerge as a leading practical alternative to classical NHCs in various aspects of catalysis, cross-coupling and C-H activation endeavors.

Dehydrogenative Pd and Ni Catalysis for Total Synthesis

The development of novel synthetic methods remains a cornerstone in simplifying complex molecule synthesis. Progress in the field of transition metal catalysis has enabled new mechanistic strategies to achieve difficult chemical transformations, increased the value of abundant chemical building blocks, and pushed the boundaries of creative and strategic route design to improve step economy in multistep synthesis. Methodologies to introduce an olefin into saturated molecules continue to be essential transformations because of the plethora of reactions available for alkene functionalization. Of particular importance are dehydrogenation reactions adjacent to electron-withdrawing groups such as carbonyls, which advantageously provide activated olefins that can be regioselectively manipulated. Palladium catalysis occupies a central role in the most widely adopted carbonyl dehydrogenation reactions, but limits to the scope of these protocols persist.In this Account, we describe our group's contributions to the area of transition-metal-catalyzed dehydrogenation using palladium catalysis and more sustainable and economical nickel catalysis. These metals are used in conjunction with allyl and aryl halides or pseudohalides that serve as oxidants to access a unique mechanistic approach for one-step α,β-dehydrogenation of various electron-withdrawing groups, including ketones, esters, nitriles, amides, carboxylic acids, and electron-deficient heteroarenes. The pivotal reaction parameters that can be modified to influence reaction efficiency are highlighted, including base and oxidant structure as well as ligand and salt additive effects. This discussion is expected to serve as a guide for troubleshooting challenging dehydrogenation reactions and provide insight for future reaction development in this area.In addition to enabling dehydrogenation reactions, our group's allyl-Pd and -Ni chemistry can be used for C-C and C-X bond-forming reactions, providing novel disconnections with practical applications for expediting multistep synthesis. These transformations include a telescoped process for ketone α,β-vicinal difunctionalization; an oxidative enone β-functionalization, including β-stannylation, β-silylation, and β-alkylation; and an oxidative cycloalkenylation between unstabilized ketone enolates and unactivated alkenes. These bond-forming methodologies broaden the range of transformations accessible from abundant ketone, enone, and alkene moieties. Both the dehydrogenation and C-C and C-X bond-forming methodologies have been implemented in our group's total synthesis campaigns to provide step-efficient synthetic routes toward diverse natural products.Through the lens of multistep synthesis, the utility and robustness of our dehydrogenation and dehydrogenative functionalization methodologies can be better appreciated, and we hope that this Account will inspire practitioners to apply our methodologies to their own synthetic challenges.

Transition metal-catalyzed synthesis of spirooxindoles

Spirooxindole is a principal bioactive agent and is observed in several natural products including alkaloids. They are broadly studied in the pharmaceutical field and have a significant role in the evolution of drugs such as anti-viral, anti-cancer, anti-microbial etc. In organic chemistry, an indispensable role is presented by transition metal catalysts. An effective synthetic perspective to spirooxindoles is the use of transition metals as the catalyst. This review discusses the synthesis of spirooxindoles catalyzed by transition metals and covers literature up to 2020.

Transamidation of Amides and Amidation of Esters by Selective N-C(O)/O-C(O) Cleavage Mediated by Air- and Moisture-Stable Half-Sandwich Nickel(II)-NHC Complexes

The formation of amide bonds represents one of the most fundamental processes in organic synthesis. Transition-metal-catalyzed activation of acyclic twisted amides has emerged as an increasingly powerful platform in synthesis. Herein, we report the transamidation of N-activated twisted amides by selective N-C(O) cleavage mediated by air- and moisture-stable half-sandwich Ni(II)-NHC (NHC = N-heterocyclic carbenes) complexes. We demonstrate that the readily available cyclopentadienyl complex, [CpNi(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), promotes highly selective transamidation of the N-C(O) bond in twisted N-Boc amides with non-nucleophilic anilines. The reaction provides access to secondary anilides via the non-conventional amide bond-forming pathway. Furthermore, the amidation of activated phenolic and unactivated methyl esters mediated by [CpNi(IPr)Cl] is reported. This study sets the stage for the broad utilization of well-defined, air- and moisture-stable Ni(II)-NHC complexes in catalytic amide bond-forming protocols by unconventional C(acyl)-N and C(acyl)-O bond cleavage reactions.

Constructing Ni-based confinement catalysts with advanced performances toward the CO2 reforming of CH4: state-of-the-art review and perspectives

The concept of Ni-based confinement catalysts has been proposed and developed to address the challenge of the thermal sintering of metallic Ni active sites during CRM by the space and/or lattice confinement effects.

Origins of Lewis acid acceleration in nickel-catalysed C–H, C–C and C–O bond cleavage

The effects of charge transfer, Pauli repulsion and electrostatics/polarization are identified as dominant factors for Lewis acid accelerations in Ni-catalyzed C–X (X = H, C and O) bond cleavages.

Recent advances in pincer-nickel catalyzed reactions

Organometallic catalysts have played a key role in accomplishing numerous synthetically valuable organic transformations that are either otherwise not possible or inefficient. The use of precious, sparse and toxic 4d and 5d metals are an apparent downside of several such catalytic systems despite their immense success over the last several decades. The use of complexes containing Earth-abundant, inexpensive and less hazardous 3d metals, such as nickel, as catalysts for organic transformations has been an emerging field in recent times. In particular, the versatile nature of the corresponding pincer-metal complexes, which offers great control of their reactivity via countless variations, has garnered great interest among organometallic chemists who are looking for greener and cheaper alternatives. In this context, the current review attempts to provide a glimpse of recent developments in the chemistry of pincer-nickel catalyzed reactions. Notably, there have been examples of pincer-nickel catalyzed reactions involving two electron changes via purely organometallic mechanisms that are strikingly similar to those observed with heavier Pd and Pt analogues. On the other hand, there have been distinct differences where the pincer-nickel complexes catalyze single-electron radical reactions. The applicability of pincer-nickel complexes in catalyzing cross-coupling reactions, oxidation reactions, (de)hydrogenation reactions, dehydrogenative coupling, hydrosilylation, hydroboration, C-H activation and carbon dioxide functionalization has been reviewed here from synthesis and mechanistic points of view. The flurry of global pincer-nickel related activities offer promising avenues in catalyzing synthetically valuable organic transformations.

Nickel-catalyzed cross-electrophile coupling of aryl bromides and cyclic secondary alkyl bromides with spiro-bidentate-pyox ligands

The cross-electrophile coupling catalyzed by nickel/spiro-bidentate-pyox ligands with lithium chloride as the additive was reported, which has good functional group tolerance (19 examples).

Fundamentals and applications of photo-thermal catalysis

Photo-thermal catalysis has recently emerged as an alternative route to drive chemical reactions using light as an energy source.

Directed design of hydrogenation Ziegler systems

We reported the concept of a directed design of multicomponent catalytic systems of the hydrogenation of unsaturated hydrocarbons.

Different effects of metal-NHC bond cleavage on the Pd/NHC and Ni/NHC catalyzed α-arylation of ketones with aryl halides

Fundamental differences in the behavior of Pd/NHC and Ni/NHC catalytic systems in ketones α-arylation were elucidated and exploited.

Ni/NHC catalysis in C–H functionalization using air-tolerant nickelocene and sodium formate for in situ catalyst generation

A facile method for Ni/NHC catalyzed C–H alkylation and alkenylation of heteroarenes with alkenes and internal alkynes using air-tolerant nickelocene, sodium formate and NHC·HCl salts for in situ catalyst generation has been developed.

Mechanisms and origins of regioselectivities of nickel-catalyzed β,δ-vinylarylation of alkenyl esters with vinyl triflates and arylzinc reagents

DFT calculations were performed to explore the mechanisms, origins of regioselectivity and substituent-controlled reactivity in the β,δ-vinylarylation of alkenyl esters catalyzed by nickel catalysts.

Reactions of nickel(0) with organochlorides, organobromides, and organoiodides: mechanisms and structure/reactivity relationships

The reactions of nickel(0) complexes with phosphine, bipyridine-type, and N-heterocyclic carbene ligands with aryl, vinyl, and alkyl halides is reviewed.

Ranking Ligands by Their Ability to Ease (C6F5)2NiIIL → Ni0L + (C6F5)2 Coupling versus Hydrolysis: Outstanding Activity of PEWO Ligands

The Ni^II literature complex cis-[Ni(C₆F₅)₂(THF)₂] is a synthon of cis-Ni(C₆F₅)₂ that allows us to establish a protocol to measure and compare the ligand effect on the Ni^II → Ni⁰ reductive elimination step (coupling), often critical in catalytic processes. Several ligands of different types were submitted to this Ni-meter comparison: bipyridines, chelating diphosphines, monodentate phosphines, PR₂(biaryl) phosphines, and PEWO ligands (phosphines with one potentially chelate electron-withdrawing olefin). Extremely different C₆F₅-C₆F₅ coupling rates, ranging from totally inactive (producing stable complexes at room temperature) to those inducing almost instantaneous coupling at 25 °C, were found for the different ligands tested. The PR₂(biaryl) ligands, very efficient for coupling in Pd, are slow and inefficient in Ni, and the reason for this difference is examined. In contrast, PEWO type ligands are amazingly efficient and provide the lowest coupling barriers ever observed for Ni^II complexes; they yield up to 96% C₆F₅-C₆F₅ coupling in 5 min at 25 °C (the rest is C₆F₅H) and 100% coupling with no hydrolysis in 8 h at -22 to -53 °C.

Nickel-catalysed chemoselective C-3 alkylation of indoles with alcohols through a borrowing hydrogen method

An inexpensive, air-stable, isolable nickel catalyst is reported that can perform chemoselective C3-alkylation of indoles with a variety of alcohols following "borrowing hydrogen". A one-pot, cascade C3-alkylation starting from 2-aminophenyl ethyl alcohols, and thus obviating the need for pre-synthesized indoles, further adds to the broad scope of this method. The reaction is radical-mediated, and is significantly different from other examples, often dictated by metal-ligand bifunctionality.

General Method for Enantioselective Three-Component Carboarylation of Alkenes Enabled by Visible-Light Dual Photoredox/Nickel Catalysis

A visible-light-promoted photoredox/nickel protocol for the enantioselective three-component carboarylation of alkenes with tertiary and secondary alkyltrifluoroborates and aryl bromides is described. This redox-neutral protocol allows for facile and divergent access to a wide array of enantioenriched β-alkyl-α-arylated carbonyls, phosphonates, and sulfones in high yields and excellent enantioselectivities from readily available starting materials. We also report a modular and enantioselective synthesis of flurbiprofen analogs and piragliatin lead compound to demonstrate synthetic utility. Experimental and computational mechanistic studies were performed to gain insights into the mechanism and origin of chemo- and enantioselectivity.

C–O Bond Activation as a Strategy in Palladium-Catalyzed Cross-Coupling

The activation of strong C–O bonds in cross-coupling catalysis can open up new oxygenate-based feedstocks and building blocks for complex-molecule synthesis. Although Ni catalysis has been the major focus for cross-coupling of carboxylate-based electrophiles, we recently demonstrated that palladium catalyzes not only difficult C–O oxidative additions but also Suzuki-type cross-couplings of alkenyl carboxylates under mild conditions. We propose that, depending on the reaction conditions, either a typical Pd(0)/(II) mechanism or a redox-neutral Pd(II)-only mechanism can operate. In the latter pathway, C–C bond formation occurs through carbopalladation of the alkene, and C–O cleavage by β-carboxyl elimination.

1 Introduction

2 A Mechanistic Challenge: Activating Strong C–O Bonds

3 Exploiting Vinylogy for C–Cl and C–O Oxidative Additions

4 An Alternative Mechanism for Efficient Cross-Coupling Catalysis

5 Conclusions and Outlook

Understanding the unique reactivity patterns of nickel/JoSPOphos manifold in the nickel-catalyzed enantioselective C-H cyclization of imidazoles

The 3d transition metal-catalyzed enantioselective C–H functionalization provides a sustainable strategy for the construction of chiral molecules. A better understanding of the catalytic nature of the reactions and the factors controlling the enantioselectivity is important for rational design of more efficient systems. Herein, the mechanisms of Ni-catalyzed enantioselective C–H cyclization of imidazoles are investigated by density functional theory (DFT) calculations. Both the π-allyl nickel(ii)-promoted σ-complex-assisted metathesis (σ-CAM) and the nickel(0)-catalyzed oxidative addition (OA) mechanisms are disfavored. In addition to the typically proposed ligand-to-ligand hydrogen transfer (LLHT) mechanism, the reaction can also proceed via an unconventional σ-CAM mechanism that involves hydrogen transfer from the JoSPOphos ligand to the alkene through P–H oxidative addition/migratory insertion, C(sp²)–H activation via σ-CAM, and C–C reductive elimination. Importantly, computational results based on this new mechanism can indeed reproduce the experimentally observed enantioselectivities. Further, the catalytic activity of the π-allyl nickel(ii) complex can be rationalized by the regeneration of the active nickel(0) catalyst via a stepwise hydrogen transfer, which was confirmed by experimental studies. The calculations reveal several significant roles of the secondary phosphine oxide (SPO) unit in JoSPOphos during the reaction. The improved mechanistic understanding will enable design of novel enantioselective C–H transformations.

Several unique reactivity patterns of the Ni/JoSPOphos manifold, including facile hydrogen transfer via the two-step oxidative addition/migratory insertion and C(sp²)–H activation via an unconventional σ-CAM mechanism, were disclosed in this work.

Reductive transformation of perfluorooctanesulfonate by nNiFe0-Activated carbon

Degradation of linear (L) and branched (Br) perfluorooctanesulfonate (PFOS) using nNiFe° particles supported on activated carbon (AC) and heat is demonstrated for the first time and with several lines of evidence. At 60 °C, PFOS degradation plateaued at 50 ± 6%, while at 50 °C, 94 ± 4.1 % PFOS transformed. The accelerated iron corrosion at the higher temperature is attributed to the lower PFOS transformation at 60 °C. However, at both temperatures, ≥ 97 % of the PFOS transformed was accounted for by the moles of fluoride generated. At 60 °C, PFOS degradation rates were estimated at 0.028 ± 0.003 h^-1 and fluoride and sulfite generation rates of 0.70 ± 0.165 h^-1 and 0.62 ± 0.157 h^-1, respectively, with no differences between L-PFOS and total Br-PFOS. Using time-of-flight mass spectrometry, some organic products were identified in the particle extracts from the 60 °C reaction. Products included single-bonded C8 polyfluoroalkyl sulfonates (F₁₆ to F₇) and alkyl acids (PFCAs, C₄-C₈) and one perfluorinated C₈ desulfonated product supporting both defluorination and desulfonation pathways. Most of the organic products were gone after the first 25 h. High PFOS mineralization using nNiFe°-AC technology warrants further investigation for its use in permeable reactive barriers.

Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)

The mechanism of the reactions between dppf-Ni0 complexes and alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(κ2-dppf)(κ1-dppf)], which undergoes a halide abstraction reaction with alkyl halides and rapidly captures the alkyl radical that is formed. The rates of the reactions of [Ni(COD)(dppf)] with alkyl halides and the yields of prototypical nickel-catalyzed Kumada cross-coupling reactions of alkyl halides are shown to be significantly improved by the addition of free dppf ligand.

Ni-Catalyzed Direct Carboxylation of an Unactivated C-H Bond with CO2

The transition-metal-catalyzed direct carboxylation of an unactivated C-H bond is rarely reported, and no example of catalysis using abundant and cheap nickel has been reported. In this work, the first Ni-catalyzed direct carboxylation of an unactivated C-H bond under an atmospheric pressure of CO₂ is reported. This method affords moderate to high carboxylation yields of various methyl carboxylates under mild conditions. Preliminary mechanistic studies reveal that a Ni(0)-Ni(II)-Ni(I) catalytic cycle may be involved in this reaction.

Ru and Ni—Privileged Metal Combination for Environmental Nanocatalysis

Privileged structures is a term that is used in drug design to indicate a fragment that is popular in the population of drugs or drug candidates that are in the application or investigation phases, respectively. Privileged structures are popular motifs because they generate efficient drugs. Similarly, some elements appear to be more efficient and more popular in catalyst design and development. To indicate this fact, we use here a term privileged metal combination. In particular, Ru-based catalysts have paved a bumpy road in a variety of commercial applications from ammonia synthesis to carbon (di)oxide methanation. Here, we review Ru/Ni combinations in order to specifically find applications in environmental nanocatalysis and more specifically in carbon (di)oxide methanation. Synergy, ensemble and the ligand effect are theoretical foundations that are used to explain the advantages of multicomponent catalysis. The economic effect is another important issue in blending metal combinations. Low temperature and photocatalytic processes can be indicated as new tendencies in carbon (di)oxide methanation. However, due to economics, future industrial developments of this reaction are still questionable.

Nickel-Catalyzed Mono-Selective α-Arylation of Acetone with Aryl Chlorides and Phenol Derivatives

The challenging nickel-catalyzed mono-α-arylation of acetone with aryl chlorides, pivalates, and carbamates has been achieved for the first time. A nickel/Josiphos-based catalytic system is shown to feature unique catalytic behavior, allowing the highly selective formation of the desired mono-α-arylated acetone. The developed methodology was applied to a variety of (hetero)aryl chlorides including biologically relevant derivatives. The methodology has been extended to the unprecedented coupling of acetone with phenol derivatives. Mechanistic studies allowed the isolation and characterization of key Ni⁰ and Ni^II catalytic intermediates. The Josiphos ligand is shown to play a key role in the stabilization of Ni^II intermediates to allow a Ni⁰ /Ni^II catalytic pathway. Mechanistic understanding was then leveraged to improve the protocol using an air-stable Ni^II pre-catalyst.

Asymmetric Synthesis of C1-Chiral THIQs with Imines in Isoquinoline Rings

Tetrahydroisoquinoline (THIQ) scaffolds are important structural units that widely exist in a variety of natural alkaloids and synthetic analogues. Asymmetric synthesis of C1-chiral THIQ is of particular importance due to its significant pharmaceutical, agrochemical, and other biological activities, and the usually distinct bioactivities exhibited by the two enantiomers. In this review, we highlight the significant advances achieved in this field, present recent asymmetric synthesis with imines in isoquinoline rings ordered according to the sequence of various substrate types. New strategies could be inspired and more types of substrates need further development.

1 Introduction

2 Catalytic Asymmetric Reaction of Dihydroisoquinolines

2.1 Asymmetric Reactions of 3,4-Dihydroisoquinolines

2.2 Asymmetric Reactions of Dihydroisoquinolinium Salts

2.3 Asymmetric Reactions of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.1 NED [3+2] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.2 IED [3+2] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.3 [3+3] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.4 [4+3] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.5 Asymmetric Addition Reactions to C,N-Cyclic N′-Acyl Azomethine Imines

2.4 Asymmetric Reactions of C,N-Cyclic Nitrones

3 Catalytic Asymmetric Mannich Reactions of Isoquinolines

4 Conclusions and Perspectives