Enantioselective Total Synthesis of (+)-Hinckdentine A via a Catalytic Dearomatization Approach

Palladium-Catalyzed Domino Heck/Cross-Coupling Cyclization Reaction: Diastereoselective Synthesis of Furan-Containing Indolines

Herein, a palladium-catalyzed diastereoselective dearomatization/cross-coupling cyclization reaction between N-arylacyl indoles and (E)-β-chlorovinyl ketones is reported. Through this cyclization/cycloisomerization cascade, a series of furan-containing indolines were obtained in yields up to 95%. The reaction features readily accessible starting materials, benzyl Pd(II)-catalyzed cycloisomerization of (E)-β-chlorovinyl ketones, the sequential formation of three bonds and bis-heterocycles, and excellent diastereoselectivity. More importantly, the carbene-secondary benzyl migratory insertion is proven to be a critical process in the sequential cyclizations.

Green synthesis for diverse bioactive benzo-fused spiroindolines through DBU-catalysed post-Ugi double cyclization

A metal-free protocol utilizing DBU catalysis for post-Ugi amide-ester exchange and Conia-ene double cyclization has been successfully developed, allowing the synthesis of diverse highly functionalized benzo-fused spiroindolines with anti-cancer activities under mild conditions. Remarkably, this methodology demonstrates promising prospects for green chemistry, as it allows for the preparation of the spiroindolines in water. Control experiments indicate that a crucial role of the cyclic imide, specifically ring rigidification, facilitates the subsequent Conia-ene cyclization.

Pd-Catalyzed Asymmetric Intramolecular Dearomatizing Reductive Heck Reaction of Indoles

An enantioselective Pd-catalyzed intramolecular dearomative reductive Heck reaction of N-(o-bromoaryl) indole-3-carboxamide is developed. By employing Pd(dba)2/SPINOL-based phosphoramidite as the chiral catalyst and HCO2Na as the hydride source, a series of enantioenriched spiro indolines bearing vicinal stereocenters were afforded in moderate to good yields with excellent enantioselectivities. The reductive Heck reaction of formal tetrasubstituted alkene bearing β-hydrogens is therefore realized by inhibiting β-H elimination.

On Demand Synthesis of C3-N1' Bisindoles by a Formal Umpolung Strategy: First Total Synthesis of (±)-Rivularin A

In this work, a straightforward synthesis of C3-N1' bisindolines is achieved by a formal umpolung strategy. The protocols were tolerant of a wide variety of substituents on the indole and indoline ring. In addition, the C3-N1' bisindolines could be converted to C3-N1' indole-indolines and C3-N1'-bisindoles. Also, we have successfully synthesized (±)-rivularin A through a biomimetic late-stage tribromination as a key step.

Enantioselective Synthesis of Isoindolinone by Palladium-Catalyzed Aminoalkynylation of O-Phenyl Hydroxamic Ethers with Alkynes

A highly efficient palladium-catalyzed asymmetric tandem aza-Heck/Sonogashira coupling reaction of O-phenyl hydroxamic ethers with terminal alkynes is described. This protocol enables versatile access to challenging chiral isoindolinone derivatives bearing a quaternary stereogenic center. The palladium-catalyzed aminoalkynylation reaction shows broad functional group tolerance and allows the straightforward preparation of isoindolinones with high efficiency and excellent enantioselectivity under mild conditions. DFT calculations were performed to disclose the reaction mechanism and the origins of the enantioselectivity.

Recent advances in Pd-catalyzed asymmetric cyclization reactions

Over the past few decades, there have been major developments in transition metal-catalyzed asymmetric cyclization reactions, enabling the convenient access to a wide spectrum of structurally diverse chiral carbo- and hetero-cycles, common skeletons found in fine chemicals, natural products, pharmaceuticals, agrochemicals, and materials. In particular, a plethora of enantioselective cyclization reactions have been promoted by chiral palladium catalysts owing to their outstanding features. This review aims to collect the latest advancements in enantioselective palladium-catalyzed cyclization reactions over the past eleven years, and it is organized into thirteen sections depending on the different types of transformations involved.

Palladium-Catalyzed Enantioselective Intramolecular Heck Dearomative Annulation of Indoles with N-Tosylhydrazones

An elegant Pd(dba)2-catalyzed enantioselective Heck dearomative annulation of indoles and N-tosylhydrazones for the straightforward assembly of structurally diverse optically active indoline scaffolds containing the quaternary carbon centers at the C2 position has been developed. The tandem protocol, which utilized a Pd(dba)2/BINOL-based phosphoramidite ligand as the catalytic system, proceeded smoothly through successive oxidative addition, intramolecular carbon palladation, migratory insertion, and β-elimination sequences, leading to the chiral indoline derivatives in moderate to excellent yields, with excellent enantioselectivities and diastereoselectivities. In addition, the synthetic practicability of the catalytic system was underlined by a scaled-up experiment and the late-stage derivatization of the products, thus highlighting the potential applications in synthetic chemistry, medicinal chemistry, and material science.

Nickel-Catalyzed Enantioselective Dearomative Heck-Reductive Allylic Defluorination Reaction of Indoles

Herein, we describe a nickel-catalyzed asymmetric dearomative aryl-difluoroallylation reaction of indoles with α-trifluoromethyl alkenes as an electrophilic coupling partner. The reaction proceeds via a cascade sequence involving dearomative Heck cyclization and reductive allylic defluorination. A series of gem-difluoroallyl substituted indolines are obtained in moderate to good yields (36-77% yield) with excellent enantioselectivity (up to 99% ee). The reaction features broad functional group tolerance, scaled-up synthesis, and late-stage diversification.

Rapid Access to 2,2-Disubstituted Indolines via Dearomative Indolic-Claisen Rearrangement: Concise, Enantioselective Total Synthesis of (+)-Hinckdentine A

The construction of 2,2-disubstituted indolines has long presented a synthetic challenge without any general solutions. Herein, we report a robust protocol for the dearomative Meerwein-Eschenmoser-Claisen rearrangement of 3-indolyl alcohols that provides efficient access to 2-substituted and 2,2-disubstituted indolines. These versatile subunits are useful for natural product synthesis and medicinal chemistry. The title [3,3] sigmatropic rearrangement proceeds in generally excellent yield and transfers the C3-indolic alcohol chirality to the C2 position with high fidelity, thus providing a reliable method for the construction of enantioenriched 2,2-disubstituted indolines. The power of this methodology is demonstrated through the concise and strategically unique total synthesis of the marine natural product hinckdentine A, which features a dearomative Claisen rearrangement, a diastereocontrolled hydrogenation of the alkene product, a one-pot amide-to-oxime conversion using Vaska's complex, and a regioselective late-stage tribromination.

Dearomatizing [2+2+1] Spiroannulation of Indoles with Alkynes

A palladium-catalyzed dearomatizing [2+2+1] spiroannulation of indoles with two molecular internal alkynes is developed in the presence of Cu(OAc)₂/O₂ as the oxidant, in which a domino sequence including C-H activation of indole followed by consecutive Heck reactions is involved. A range of 3,3'-spiroindolines bearing tetrasubstituted cyclopentadiene moieties and exocyclic C═C bonds at C2 are obtained in moderate to excellent yields.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Dearomative logic in natural product total synthesis

Covering: 2011 to 2022The natural world is a prolific source of some of the most interesting, rare, and complex molecules known, harnessing sophisticated biosynthetic machinery evolved over billions of years for their production. Many of these natural products represent high-value targets of total synthesis, either for their desirable biological activities or for their beautiful structures outright; yet, the high sp³-character often present in nature's molecules imparts significant topological complexity that pushes the limits of contemporary synthetic technology. Dearomatization is a foundational strategy for generating such intricacy from simple materials that has undergone considerable maturation in recent years. This review highlights the recent achievements in the field of dearomative methodology, with a focus on natural product total synthesis and retrosynthetic analysis. Disconnection guidelines and a three-phase dearomative logic are described, and a spotlight is given to nature's use of dearomatization in the biosynthesis of various classes of natural products. Synthetic studies from 2011 to 2021 are reviewed, and 425 references are cited.

Palladium-Catalyzed Intramolecular Heck Dearomative Alkenylation of Indoles with N-Tosylhydrazones

An elegant Pd-catalyzed intramolecular Heck dearomative alkenylation of aryl iodides with functionalized N-tosylhydrazones proceeded through a sequential dearomative carbopalladation, migratory insertion, and β-hydride elimination in the presence of Pd(CF₃COO)₂ (10 mol %), PPh₃ (30 mol %), and Cs₂CO₃ (2.0 equiv) in 1,4-dioxane (2.0 mL) at 120 °C for 14 h under an argon atmosphere. This cascade cycloaddition protocol provided a reliable and versatile approach to a sequence of structurally diverse indolines in moderate to good yields with good functional group compatibility. In addition, the synthetic robustness of the methodology is highlighted by a scaled-up experiment and derivatization of products via epoxidation and reduction reactions.

Condition-Dependent Selective Synthesis of Indolo[1,2-c]quinazolines and Indolo[3,2-c]quinolines from 2-(1H-Indol-2-yl)anilines and Sulfoxonium Ylides

In this paper, a selective synthesis of indolo[1,2-c]quinazolines and indolo[3,2-c]quinolines through the cascade reactions of 2-(1H-indol-2-yl)anilines with sulfoxonium ylides is presented. The formation of products involves the generation of a carbene species from sulfoxonium ylide and its N-H bond insertion reaction with 2-(1H-indol-2-yl)aniline followed by deoxygenative imine formation, intramolecular N- or C- nucleophilic addition and deoxygenative aromatization. This switchable synthesis was condition-dependent. In the presence of K₂CO₃ in CH₃CN, the reaction mainly furnished indolo[1,2-c]quinazolines. In the presence of HOAc in dioxane, it selectively afforded indolo[3,2-c]quinolines. In addition, direct C-H/N-H functionalization of the products obtained provides a convenient and direct access to polycyclic heteroaromatic compounds. These novel protocols have advantages such as readily accessible substrates, easily tunable selectivity, good compatibility with diverse functional groups, and the use of air as a cost-free and sustainable oxidant.

Indole Editing Enabled by HFIP-Mediated Ring-Switch Reactions of 3-Amino-2-Hydroxyindolines

This work reports the novel reactivity of hemiaminal as a precursor for indole editing at the multi-site. The HFIP-promoted indole editing of indoline hemiaminals affords 2-arylindoles through a ring-switch sequence. The key to success of this transformation is to use a cyclic hemiaminal as an α-amino aldehyde surrogate under transient tautomeric control. This transformation features mild reaction conditions and good yields with broad functional group tolerance. The utility of this transformation is presented through the one-pot protocol and the synthesis of isocryptolepine.

Enantioselective Pd-catalyzed dearomative reductive Heck and domino Heck-Suzuki reactions of 2-CF3-indoles

Highly enantioselective palladium-catalyzed dearomative reductive Heck reaction and domino Heck-Suzuki reaction of 2-CF₃-indoles have been developed. Using Pd(OAc)₂/(R)-Synphos as the catalyst and Et₃SiH as a hydride source, a variety of indolines bearing a 2-trifluoromethyl quaternary stereocenter were obtained via a dearomative reductive Heck reaction. Alternatively, using Pd(dba)₂/phosphoramidite as the catalyst and Ar₄BNa as a coupling partner, structurally diverse indolines containing two vicinal carbon stereocenters were afforded through the domino dearomative Heck-Suzuki reaction.

Dearomative Iodocyclization of N-(o-Alkynyl)aryl Isoindole

We present a dearomative iodocyclization of N-(o-alkynyl)aryl isoindole here, which affords various biologically active benzoindoleazine skeletons containing alkenyl iodine. The products can further undergo cycloaddition or coupling reactions to afford a series of highly functionalized N-fused polycyclic scaffolds.

Total Synthesis of (+)-Hinckdentine A: Harnessing Noncovalent Interactions for Organocatalytic Bromination

Hinckdentine A, a marine-sponge-derived tribrominated indole alkaloid bearing a unique indolo[1,2-c]quinazoline skeleton, was completed in 12 steps featuring the construction of the Nα-quaternary carbon center by asymmetric azo-ene cyclization. A novel organocatalyst was developed to promote high-yielding tribromination, which represents a challenging process encountered in previous syntheses. Density functional theory calculations scrutinized viable substrates and deciphered the origin of the enhancement of C8 electrophilic bromination with a bifunctional organocatalyst. Moreover, the application of organocatalyst-enabled bromination on various substrates was demonstrated to highlight future late functionalizations of biologically intriguing targets.

Palladium-Catalyzed Asymmetric Dearomative Carbonylation of Indoles

Herein, we disclose a strategy for the asymmetric dearomatization of N-arylacyl indoles via a palladium-catalyzed tandem Heck/carbonylation, leading to an array of indoline-3-carboxylates bearing vicinal C2-aza-quaternary and C3 tertiary stereocenters in high yields and excellent enantio- and diastereoselectivities. This study is an important advance in the field of asymmetric carbonylation and enantioselective dearomatization reactions.

Aromatic π-Components for Enantioselective Heck Reactions and Heck/Anion-Capture Domino Sequences

Olefin functionalization represents one of the most important synthetic transformations in organic synthesis. Over the past decades, palladium-catalyzed enantioselective Heck reactions, and Heck/anion-capture domino sequences through olefin carbopalladation followed by termination of the resulting alkyl-Pd species have been extensively developed. Extension of the coupling partners from classical olefins to other π-components would enable further advances and open new space in this field. Aromatics are important and easily available bulk chemicals. Dearomative transformation of endocyclic aromatic π-bonds via the Heck reaction pathway provides an efficient and straightforward route to structurally diverse alicyclic compounds. Nevertheless, major challenges for this transformation include aromaticity breaking and reactivity and selectivity issues.Recently, we have engaged in developing catalytic enantioselective dearomative Heck reactions and related domino reactions. A range of heteroarenes and naphthalenes have been employed as novel π-coupling partners in these reactions. Through dearomative migratory insertion of endocyclic aromatic C-C π-bonds followed by interception of the transient alkyl-Pd species, enantioselective Heck reactions, reductive Heck reactions, Heck/anion-capture difunctionalization reactions, and heteroarenyne cycloisomerization reactions have been established. Relying on β-H elimination of the alkyl-Pd intermediate, we realized enantioselective dearomative Heck reactions with a range of aromatic partners, including heterocyclic indoles, pyrroles, furans, benzofurans, and more challenging carbocyclic naphthalenes. In order to avoid the utilization of organohalide electrophiles, heteroarenyne cycloisomerization reaction was developed by merging intermolecular alkyne hydropalladation with intramolecular dearomative Heck reaction. Cycloisomerization of alkyne-tethered indoles delivered chiral indolines in excellent enantioselectivities with 100% atom economy. On the other hand, Heck/anion-capture domino sequences were established through nucleophilic trapping of the alkyl-Pd intermediate. When HCO₂Na was employed as a capturing reagent, the enantioselective dearomative reductive Heck reaction of indoles was realized. By employing other nucleophiles, including alkynes, N-sulfonylhydrazones, and organoboron reagents, we developed a series of dearomative difunctionalization reactions. Two vicinal stereocenters with excellent enantio- and diastereoselectivities were constructed in the corresponding Heck/Sonogashira, Heck/vinylation, and Heck/borylation reactions. Moreover, dearomative 1,4-diarylation of naphthalenes was developed through Heck/Suzuki domino reactions, in which competitive C-H arylation and the direct Suzuki reaction were almost fully inhibited in the presence of a spiro-phosphoramidite ligand.In this Account, we provide a panoramic view of our results since 2015 on enantioselective Heck reactions and related domino sequences by extending the coupling partners from classical olefins to aromatic systems. Investigations outlined in this Account established straightforward and efficient access to a variety of structurally diverse chiral heteropolycyclic molecules starting from simple and planar aromatic compounds.

Synthesis of pyrimidine-containing alkaloids

This review deals with the synthesis of naturally occurring alkaloids containing partially or completely saturated pyrimidine nuclei. The interest in these compounds is associated with their structural diversity, high biological activity and toxicity. The review is divided into four parts, each of which describes a number of synthetic methodologies toward structurally different naturally occurring alkaloids containing saturated cyclic six-membered amidine, guanidine, aminal and urea (thiourea) moieties, respectively. The development of various synthetic strategies for the preparation of these compounds has remarkably increased during the past few decades. This is primarily due to the fact that some of these compounds are isolated only in limited quantities, which makes it practically impossible to study their full structural characteristics and biological activity.

Visible-Light-Driven Palladium-Catalyzed Radical Tandem Dearomatization of Indoles with Unactivated Alkenes

A mild visible-light-driven palladium-catalyzed radical tandem dearomatization of indoles with unactivated alkenes is described with moderate to good yields and good to excellent diastereoselectivities. Under visible-light irradiation, the photoexcited state of the palladium complex was formed, which could transfer a single electron to N-(2-bromobenzoyl)indoles, leading to a hybrid palladium radical chemistry. This provides efficient and atom-economical access to diverse 2,3-disubstituted indoline derivatives.

Enantioselective Dearomative [3 + 2] Umpolung Annulation of N-Heteroarenes with Alkynes

Enantioselective [3 + 2] annulation of N-heteroarenes with alkynes has been developed via a cobalt-catalyzed dearomative umpolung strategy in the presence of chiral ligand and reducing reagent. A variety of electron-deficient N-heteroarenes, including quinolines, isoquinolines, quinoxaline, and pyridines, and internal or terminal alkynes are employed in this reaction, showing a broad substrate scope and good functionality tolerance. Annulation of electron-rich indoles with alkynes is also developed. This protocol provides a straightforward access to a variety of N-spiroheterocyclic molecules in excellent enantioselectivities (76 examples, up to 99% ee).

Palladium-catalyzed intramolecular Heck dearomative gem-difluorovinylation of indoles

A palladium-catalyzed dearomative reaction of indoles has been developed through a domino Heck/gem-difluorovinylation sequence. By taking advantage of a difluorocarbene precursor (ClCF₂COONa), the palladium difluorocarbene ([Pd] Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CF₂) species was formed smoothly. Then, a migratory insertion/β-H elimination process enabled access to polycyclic indolines containing 1,1-difluoroethylene units in acceptable yields with a broad substrate scope, which also showed dearomative gem-difluorovinylation for the first time. Remarkably, the superb diversified transformations allowed the product to install various functional groups.

Dearomative gem-difluorovinylation was reported for the first time and provided a new way to construct complex organofluorine compounds rapidly.

Enantioselective Total Synthesis of Cepharatines via Bioinspired Ring Reconstruction

We describe enantioselective total syntheses of cepharatines A-D, members of the hasubanan alkaloid family, which feature an unusual tetracyclic skeleton including an azabicyclo[3.3.1]nonane motif. A key reaction is a regio-divergent oxidative phenolic coupling reaction that affords the tricyclic core structure of hasubanan with different substitution patterns on the A-ring, including the all-carbon quaternary stereogenic center at C13, in a single step. The characteristic tetracyclic azabicyclo[3.3.1]nonane motif was constructed by means of a bioinspired cascade reaction involving the retro-aza-Michael reaction/hemiaminal formation.

Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds

The photo-induced cleavage of C(sp2)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence. The photochemical reaction tolerates a panel of functional groups including esters, alcohols, amides, cyano and alkenes (27 examples, 50-88% yields), and can be used to prepare polycyclic compounds and perform the functionalization of natural product analogues in moderate to good yields. Mechanistic experiments, including time-resolved absorption spectroscopy, are supportive of photo-induced electron transfer between the indole substrate and DIPEA, with the formation of radical intermediates in the photo-induced dearomatization reaction.

Acyclic Twisted Amides

In this contribution, we provide a comprehensive overview of acyclic twisted amides, covering the literature since 1993 (the year of the first recognized report on acyclic twisted amides) through June 2020. The review focuses on classes of acyclic twisted amides and their key structural properties, such as amide bond twist and nitrogen pyramidalization, which are primarily responsible for disrupting n_N to π*_C═O conjugation. Through discussing acyclic twisted amides in comparison with the classic bridged lactams and conformationally restricted cyclic fused amides, the reader is provided with an overview of amidic distortion that results in novel conformational features of acyclic amides that can be exploited in various fields of chemistry ranging from organic synthesis and polymers to biochemistry and structural chemistry and the current position of acyclic twisted amides in modern chemistry.

Recent advances in the synthesis of pyrrolo[1,2-a]indoles and their derivatives

The pyrrolo[1,2-a]indole unit is a privileged heterocycle found in numerous natural products and has been shown to exhibit diverse pharmacological properties. Thus, recent years have witnessed immense interest from the synthesis community on the synthesis of this scaffold. In light of the ever-increasing demand for pyrrolo[1,2-a]indoles in drug discovery, this review provides an overview of recent synthesis methods for the preparation of pyrrolo[1,2-a]indoles and their derivatives. The mechanistic pathway and stereo-electronic factors affecting the yield and selectivity of the product are briefly explained. Furthermore, we have attempted to demonstrate the utility of the developed methods in the synthesis of bioactive molecules and natural products, wherever offered.

Enolate-Based Regioselective Anti-Beckmann C-C Bond Cleavage of Ketones

The Baeyer-Villiger or Beckmann rearrangements are established methods for the cleavage of ketone derivatives under acidic conditions, proceeding for unsymmetrical precursors selectively at the more substituted site. However, the fragmentation regioselectivity cannot be switched and fragmentation at the less-substituted terminus is so far not possible. We report here that the reaction of ketone enolates with commercial alkyl nitrites provides a direct and regioselective way of fragmenting ketones into esters and oximes or ω-hydroxyimino esters, respectively. A comprehensive study of the scope of this reaction with respect to ketone classes and alkyl nitrites is presented. Control over the site of cleavage is gained through regioselective enolate formation by various bases. Oxidation of kinetic enolates of unsymmetrical ketones leads to the otherwise unavailable "anti-Beckmann" cleavage at the less-substituted side chain, while cleavage of thermodynamic enolates of the same ketones represents an alternative to the Baeyer-Villiger oxidation or the Beckmann rearrangement under basic conditions. The method is suited for the transformation of natural products and enables access to orthogonally reactive dicarbonyl compounds.

Dearomatization through Photoredox Hydroarylation: Discovery of a Radical-Polar Crossover Strategy

Indole dearomatization has been achieved via radical hydroarylation. Under mild photoredox conditions, a range of indole derivatives undergo hydroarylation to form 2-arylindoline products. Mechanistically, radical termination occurs primarily via stepwise reduction/protonation, with a small contribution from concerted hydrogen atom transfer. This mechanistic understanding prompted the extension of this reactivity to benzenoid dearomatization. This work formed the foundation of our program, which utilizes reductive radical-polar crossover to drive highly selective dearomatization pathways.

Diastereoselective Access to Tetracyclic Eight-Membered Lactams through a Dearomative Heck Reaction and an Alkylative Ring-Opening Driven by Photoexcited Spiroindolines

An external-photocatalyst-free, light-driven alkylative ring-opening of stable spiroindolines was developed to construct indolo- and benzoannulated eight-membered lactams. The spiroindolines were prepared from tetrahydro-β-carbolines by a dearomative Heck reaction. Mechanistic experimental studies on the alkylative ring opening suggested that a photoredox pathway was involved, in which the spiroindoline performed as both reagent and photosensitizer. DFT calculations showed that the radical addition toward a cyclic alkene was the key to the diastereoselective formation of tetracyclic medium-sized lactams.

Construction of Indoline/Indolenine Ring Systems by a Palladium-Catalyzed Intramolecular Dearomative Heck Reaction and the Subsequent Aza-semipinacol Rearrangement

The palladium-catalyzed intramolecular dearomative Heck reaction of 2,3-disubstituted indoles serves as an access to spiro-indoline products. Herein, we report an efficient construction of indoline/indolenine core stuctures via a dearomative Heck reaction of simple 2,3-disubstituted indoles with all-carbon tethers and the subsequent aza-semipinacol rearrangement. The Heck reaction features a high C2-selectivity, and the stereospecific aryl/alkyl migration selectivity has been investigated by DFT calculations. Using this method, we accomplished the formal total synthesis of akuammiline alkaloids vincorine.

Isoindolinone Synthesis via One-Pot Type Transition Metal Catalyzed C-C Bond Forming Reactions

Isoindolinone structure is an important privileged scaffold found in a large variety of naturally occurring as well as synthetic, biologically and pharmaceutically active compounds. Owing to its crucial role in a number of applications, the synthetic methodologies for accessing this heterocyclic skeleton have received significant attention during the past decade. In general, the synthetic strategies can be divided into two categories: First, direct utilization of phthalimides or phthalimidines as starting materials for the synthesis of isoindolinones; and second, construction of the lactam and/or aromatic rings by different catalytic methods, including C-H activation, cross-coupling, carbonylation, condensation, addition and formal cycloaddition reactions. Especially in the last mentioned, utilization of transition metal catalysts provides access to a broad range of substituted isoindolinones. Herein, the recent advances (2010-2020) in transition metal catalyzed synthetic methodologies via formation of new C-C bonds for isoindolinones are reviewed.

Total Synthesis of Hinckdentine A

The total synthesis of (±)-hinckdentine A is described herein. A cyanide-catalyzed imino-Stetter reaction of the aldimine derived from ethyl 2-amino-3,5-dibromocinnamate and 5-bromo-2-nitrobenzaldehyde followed by oxidative rearrangement afforded a 2,2-disubstituted 3-indolinone derivative containing the carbon skeleton and all of the functional groups present in the natural product correctly positioned, including three bromine atoms. Subsequent D-ring formation and seven-membered C-ring construction completed the total synthesis of hinckdentine A.

Recent advances in total syntheses of natural products containing the benzocycloheptane motif

Covering: 2010 to 2020Benzocycloheptane is a fundamental and unique structural motif found in pharmaceuticals and natural products. The total syntheses of natural products bearing the benzocycloheptane subunit are challenging and there are only a few efficient approaches to access benzocycloheptane. Thus, new methods and innovative strategies for preparing such natural products need to be developed. In this review, recent progress in the total syntheses of natural products bearing the benzocycloheptane motif is presented, and key transformations for the construction of benzocycloheptane are highlighted. This review provides a useful guide for those engaged in the syntheses of natural products containing the benzocycloheptane motif.

Pd-Catalyzed Asymmetric Dearomatization of Indoles via Decarbonylative Heck-Type Reaction of Thioesters

We report herein a palladium-catalyzed ligand-promoted asymmetric dearomatization of indoles via the decarbonylation of thioesters and the subsequent reductive Heck reaction. This protocol provides a facile and efficient way to construct an aza-quaternary stereocenter at the C2 position of indolines. A variety of functional groups and substitutions could be well tolerated, affording the substituted indolines with high enantioselectivities.