Highly convergent total synthesis of (+)-lithospermic acid via a late-stage intermolecular C-H olefination

Base-Mediated Annulation of ortho-Iminophenols and ortho-Vinylphenols with MBH Carbonates of Isatins: Straightforward Access to Dihydrobenzofuran and Benzofuran Derivatives

We have developed a convenient synthetic protocol for efficient construction of significant dihydrobenzofuran and benzofuran scaffolds by Lewis base-mediated annulation reaction ortho-iminophenols and ortho-vinylphenols with MBH carbonates of isatins under mild and metal-free conditions. The selective generation of different kinds of dihydrobenzofuran and benzofuran derivatives was successfully achieved by employing different substituted isatin-derived MBH carbonates with ortho-N-tosyliminophenols and ortho-vinylphenols. The features included broad substrate scopes, excellent functional group compatibility, high molecular diversity, and atomic economy.

Development of novel transition metal-catalyzed synthetic approaches for the synthesis of a dihydrobenzofuran nucleus: a review

The synthesis of dihydrobenzofuran scaffolds bears pivotal significance in the field of medicinal chemistry and organic synthesis. These heterocyclic scaffolds hold immense prospects owing to their significant pharmaceutical applications as they are extensively employed as essential precursors for constructing complex organic frameworks. Their versatility and importance make them an interesting subject of study for researchers in the scientific community. While exploring their synthesis, researchers have unveiled various novel and efficient pathways for assembling the dihydrobenzofuran core. In the wake of extensive data being continuously reported each year, we have outlined the recent updates (post 2020) on novel methodological accomplishments employing the efficient catalytic role of several transition metals to forge dihydrobenzofuran functionalities.

Catalytic asymmetric carbenoid α-C-H insertion of ether

Significant advancements have been made in catalytic asymmetric α-C-H bond functionalization of ethers via carbenoid insertion over the past decade. Effective asymmetric catalytic systems, featuring a range of chiral metal catalysts, have been established for the enantioselective synthesis of diverse ether substrates. This has led to the generation of various enantioenriched, highly functionalized oxygen-containing structural motifs, facilitating their application in the asymmetric synthesis of bioactive natural products.

Cobalt-Catalyzed Enantioselective C-H Annulation of Benzylamines with Alkynes: Application to the Modular and Asymmetric Syntheses of Bioactive Molecules

The transition metal-catalyzed enantioselective C-H functionalization strategy has revolutionized the logic of natural product synthesis. However, previous applications have heavily relied on the use of noble metal catalysts such as rhodium and palladium. Herein, we report the efficient synthesis of C1-chiral 1,2-dihydroisoquinolines (DHIQs) via enantioselective C-H/N-H annulation of picolinamides with alkynes catalyzed by a more sustainable and cheaper 3d metal catalyst, cobalt(II) acetate tetrahydrate. A wide range of enantiomerically enriched DHIQs were obtained in good yields with excellent enantioselectivities (up to 98% yield and >99% ee). The robustness and synthetic potential of this method were demonstrated by the modular and asymmetric syntheses of several tetrahydroisoquinoline alkaloids, including (S)-norlaudanosine, (S)-laudanosine, (S)-xylopinine, (S)-sebiferine, and (S)-cryptostyline II, and the asymmetric syntheses of key intermediates of (+)-solifenacin, FR115427, and (+)-NPS R-568.

Transition-metal catalyzed C-H activation as a means of synthesizing complex natural products

Over the past few decades, the advent of C-H activation has led to a rethink among chemists about the synthetic strategies employed for multi-step transformations. Indeed, deploying innovative and masterful tricks against the numerous classical organic transformations has been the need of the hour. Despite this, the immense importance of C-H activation remains unfulfilled unless the methodology can be deployed for large-scale industrial processes and towards the concise, step-economic synthesis of prodigious natural products and pharmaceutical drugs. Lately, the growing potential of C-H activation methodology has indeed driven the pioneers of synthetic organic chemists into finding more efficient methods to accelerate the synthesis of such complex molecular scaffolds. This review aims to draw a general overview of the various C-H activation procedures that have been adopted for synthesizing these vast majority of structurally complicated natural products. Our objective lies in drawing a complete picture and taking the readers through the synthesis of a series of such complex organic compounds by simplified techniques, making it step-economic on a larger scale and thus instigating the readers to trigger the use of such methodology and uncover new, unique patterns for future synthesis of such natural products.

Kinetic Resolution of β-Alkyl Phenylethylamine Derivatives through Palladium-Catalyzed, Nosylamide-Directed C-H Olefination

Palladium-catalyzed C-H activation reactions have attracted the attention of organic researchers due to their unique high selectivity, broad functional group tolerance, and high efficiency, and they are widely used in natural products and asymmetric synthesis. Here, we report an example of enantioselective C-H alkenylation between β-alkyl phenylethylamine compounds and styrenes with Boc-L-lle-OH as the ligand and nosylamide as the directing group. This reaction is applicable to styrene containing various electron-deficient and electron-donating substitutions and may be utilized for the synthesis of benzoazepine compounds.

An Access to Highly Functionalized Dihydrobenzofuran Spirooxindole Scaffolds

We have developed an efficient protocol for the construction of polycyclic dihydrobenzofuran spirooxindole scaffolds via base promoted cascade annulation of Morita-Baylis-Hillman (MBH) carbonates of isatins with ortho-hydroxychalcones or ortho-hydroxy-β-nitrostyrenes. The complex polycyclic compounds were conveniently synthesized in satisfactory yields and with high diastereoselectivity. This protocol provides a swift and convenient approach for the assembly of diverse highly functionalized dihydrobenzofuran spirooxindoles and also features broad substrate scope, high molecular convergence, and excellent atomic economy.

Non-directed Pd-catalysed electrooxidative olefination of arenes

The Fujiwara-Moritani reaction is a powerful tool for the olefination of arenes by Pd-catalysed C-H activation. However, the need for superstoichiometric amounts of toxic chemical oxidants makes the reaction unattractive from an environmental and atom-economical view. Herein, we report the first non-directed and regioselective olefination of simple arenes via an electrooxidative Fujiwara-Moritani reaction. The versatility of this operator-friendly approach was demonstrated by a broad substrate scope which includes arenes, heteroarenes and a variety of olefins. Electroanalytical studies suggest the involvement of a Pd(ii)/Pd(iv) catalytic cycle via a Pd(iii) intermediate.

Bioinspired Palladium-Catalyzed Intramolecular C(sp3 )-H Activation for the Collective Synthesis of Proline Natural Products

Bioinspired palladium-catalyzed intramolecular cyclization of amino acid derivatives containing a vinyl iodide moiety by C-H activation enabled rapid access to a wide range of functionalized proline derivatives with an exocyclic olefin. To demonstrate the practicality of this methodology, the functionalized prolines were used as intermediates for the synthesis of several natural products: lucentamycin A, oxotomaymycin, oxoprothracarcin, and barmumycin.

Recent advances in transition-metal-catalyzed carbene insertion to C-H bonds

C-H functionalization has been emerging as a powerful method to establish carbon-carbon and carbon-heteroatom bonds. Many efforts have been devoted to transition-metal-catalyzed direct transformations of C-H bonds. Metal carbenes generated in situ from transition-metal compounds and diazo or its equivalents are usually applied as the transient reactive intermediates to furnish a catalytic cycle for new C-C and C-X bond formation. Using this strategy compounds from unactivated simple alkanes to complex molecules can be further functionalized or transformed to multi-functionalized compounds. In this area, transition-metal-catalyzed carbene insertion to C-H bonds has been paid continuous attention. Diverse catalyst design strategies, synthetic methods, and potential applications have been developed. This critical review will summarize the advance in transition-metal-catalyzed carbene insertion to C-H bonds dated up to July 2021, by the categories of C-H bonds from aliphatic C(sp³)-H, aryl (aromatic) C(sp²)-H, heteroaryl (heteroaromatic) C(sp²)-H bonds, alkenyl C(sp²)-H, and alkynyl C(sp)-H, as well as asymmetric carbene insertion to C-H bonds, and more coverage will be given to the recent work. Due to the rapid development of the C-H functionalization area, future directions in this topic are also discussed. This review will give the authors an overview of carbene insertion chemistry in C-H functionalization with focus on the catalytic systems and synthetic applications in C-C bond formation.

Pd-catalysed C-H functionalisation of free carboxylic acids

Pd-catalysed C-H functionalisation of free carboxylic acids has drawn significant attention over the last few years due to the predominance of carboxylic acid moieties in pharmaceuticals and agrochemicals. But their coordinating ability was overlooked and masked by exogenous directing groups for a long time. Even other crucial roles of carboxylic acids as additives and steric inducers that directly influence the mode of a reaction have been widely neglected. This review aims to embrace all of the diverse aspects of carboxylic acids except additive and steric effects by concisely and systematically describing their versatile role in Pd-catalysed proximal and distal C-H activation reactions that could be implemented in the pharmaceutical and agrochemical industries. In addition, the mechanistic perspectives along with several recent strategies developed in the last few years discussed here will serve as educational resources for future research.

The emergence of the C-H functionalization strategy in medicinal chemistry and drug discovery

Owing to the market competitiveness and urgent societal need, an optimum speed of drug discovery is an important criterion for successful implementation. Despite the rapid ascent of artificial intelligence and computational and bioanalytical techniques to accelerate drug discovery in big pharma, organic synthesis of privileged scaffolds predicted in silico for in vitro and in vivo studies is still considered as the rate-limiting step. C-H activation is the latest technology added into an organic chemist's toolbox for the rapid construction and late-stage modification of functional molecules to achieve the desired chemical and physical properties. Particularly, elimination of prefunctionalization steps, exceptional functional group tolerance, complexity-to-diversity oriented synthesis, and late-stage functionalization of privileged medicinal scaffolds expand the chemical space. It has immense potential for the rapid synthesis of a library of molecules, structural modification to achieve the required pharmacological properties such as absorption, distribution, metabolism, excretion, toxicology (ADMET) and attachment of chemical reporters for proteome profiling, metabolite synthesis, etc. for preclinical studies. Although heterocycle synthesis, late-stage drug modification, ¹⁸F labelling, methylation, etc. via C-H functionalization have been reviewed from the synthetic standpoint, a general overview of these protocols from medicinal and drug discovery aspects has not been reviewed. In this feature article, we will discuss the recent trends of C-H activation methodologies such as synthesis of medicinal scaffolds through C-H activation/annulation cascade; C-H arylation for sp²-sp² and sp²-sp³ cross-coupling; C-H borylation/silylation to introduce a functional linchpin for further manipulation; C-H amination for N-heterocycles and hydrogen bond acceptors; C-H fluorination/fluoroalkylation to tune polarity and lipophilicity; C-H methylation: methyl magic in drug discovery; peptide modification and macrocyclization for therapeutics and biologics; fluorescent labelling and radiolabelling for bioimaging; bioconjugation for chemical biology studies; drug-metabolite synthesis for biodistribution and excretion studies; late-stage diversification of drug-molecules to increase efficacy and safety; cutting-edge DNA encoded library synthesis and improved synthesis of drug molecules via C-H activation in medicinal chemistry and drug discovery.

Advancing the Logic of Chemical Synthesis: C-H Activation as Strategic and Tactical Disconnections for C-C Bond Construction

The design of synthetic routes by retrosynthetic logic is decisively influenced by the transformations available. Transition-metal-catalyzed C-H activation has emerged as a powerful strategy for C-C bond formation, with myriad methods developed for diverse substrates and coupling partners. However, its uptake in total synthesis has been tepid, partially due to their apparent synthetic intractability, as well as a lack of comprehensive guidelines for implementation. This Review addresses these issues and offers a guide to identify retrosynthetic opportunities to generate C-C bonds by C-H activation processes. By comparing total syntheses accomplished using traditional approaches and recent C-H activation methods, this Review demonstrates how C-H activation enabled C-C bond construction has led to more efficient retrosynthetic strategies, as well as the execution of previously unattainable tactical maneuvers. Finally, shortcomings of existing processes are highlighted; this Review illustrates how some highlighted total syntheses can be further economized by adopting next-generation ligand-enabled approaches.

TfOH-Catalyzed [4 + 1] Annulation of p-Quinone Methides with α-Aryl Diazoacetates: Straightforward Access to Highly Functionalized 2,3-Dihydrobenzofurans

We have developed a methodology for the greatly efficient construction of significant 2,3-dihydrobenzofuran scaffolds bearing a quaternary carbon center at the C2 position by means of [4 + 1] annulation reactions between p-quinone methides and α-aryl diazoacetates as C1 synthons through organocatalysis by readily accessible TfOH catalyst under mild and transition metal-free conditions. This metal-free protocol furnishes an operationally simple and swift process for the free assembly of diverse highly functionalized 2,3-dihydrobenzofurans and also features broad substrate scope, excellent functional group compatibility, and environmental friendliness. Mechanistic investigation suggested that the reaction undergoes a rapid cascade protonation/intermolecular Michael addition/intramolecular substitution process.

Rapid Construction of Tetralin, Chromane, and Indane Motifs via Cyclative C-H/C-H Coupling: Four-Step Total Synthesis of (±)-Russujaponol F

The development of practical C-H/C-H coupling reactions remains a challenging yet appealing synthetic venture because it circumvents the need to prefunctionalize both coupling partners for the generation of C-C bonds. Herein we report a cyclative C(sp³)-H/C(sp²)-H coupling reaction of free aliphatic acids enabled by a cyclopentane-based mono-N-protected β-amino acid ligand. This reaction uses inexpensive sodium percarbonate (Na₂CO₃·1.5H₂O₂) as the sole oxidant and generates water as the only byproduct. A range of biologically important scaffolds, including tetralins, chromanes, and indanes, can be easily prepared by this protocol. Finally, the synthetic application of this methodology is demonstrated by the concise total synthesis of (±)-russujaponol F in a four-step sequence starting from readily available phenylacetic acid and pivalic acid through sequential functionalizations of four C-H bonds.

Visible Light-Induced Radical Addition/Annulation to Construct Phenylsulfonyl-Functionalized Dihydrobenzofurans Involving an Intramolecular 1,5-Hydrogen Atom Transfer Process

A visible light-induced radical cascade reaction of 2-alkynylarylethers with sodium sulfinates was established for the synthesis of sulfonyl-functionalized dihydrobenzofurans, and an intramolecular 1,5-hydrogen atom transfer was involved in this transformation. This process provided an efficient and convenient C-C formation protocol for the construction of a dihydrobenzofuran ring. Various substituents on 2-alkynylarylethers and sodium sulfinates were tolerated in the reaction, and the corresponding products were obtained in moderate to good yields.

Synthesis of γ-Lactams via Pd(II)-Catalyzed C(sp3)-H Olefination Using a Self-Cleaving Polyfluoroethylsulfinyl Directing Group

A monodentate directing group, 2-chlorotetrafluoroethylsulfinylmide (-NHSOCF₂CF₂Cl), for inert C(sp³)-H bond activation is reported. This directing group shows efficient ability in Pd(II)-catalyzed C(sp³)-H olefination. The desired olefination products undergo subsequent Michael addition and in situ expulsion of the auxiliary to provide the free NH γ-lactam products. Preliminary mechanistic studies reveal that the auxiliary group is crucial for C(sp³)-H activation.

Multiple Catalytic C-H Bond Functionalization for Natural Product Synthesis

In the past decade, multiple catalytic C-H bond functionalization has been successfully applied in natural product synthesis as a strategy to reduce the number of steps, increase overall yield and employ more easily available starting materials. This minireview presents selected examples making use of multiple C-H bond functionalization in conceptually different ways. First, linear syntheses are discussed, wherein multiple C-H functionalization is employed either from simple (hetero)cyclic cores, at a late stage, or to build polycyclic systems. Second, the use of multiple C-H functionalization as a strategic tool in convergent synthesis to access and couple complex fragments is discussed. Information on the scalability of the employed methods is provided when available. The presented cases indicate that multiple C-H functionalization strategies should play a great role to shape the future synthesis of functional complex molecules with improved sustainability.

Chrysomycin A Derivatives for the Treatment of Multi-Drug-Resistant Tuberculosis

Tuberculosis (TB) is a life-threatening disease resulting in an estimated 10 million new infections and 1.8 million deaths annually, primarily in underdeveloped countries. The economic burden of TB has been estimated as approximately 12 billion USD annually in direct and indirect costs. Additionally, multi-drug-resistant (MDR) and extreme-drug-resistant (XTR) TB strains resulting in about 250 000 deaths annually are now widespread, increasing pressure on the identification of new anti-TB agents that operate by a novel mechanism of action. Chrysomycin A is a rare C-aryl glycoside first discovered over 60 years ago. In a recent high-throughput screen, we found that chrysomycin A has potent anti-TB activity, with minimum inhibitory concentration (MIC) = 0.4 μg/mL against MDR-TB strains. However, chrysomycin A is obtained in low yields from fermentation of Streptomyces, and the mechanism of action of this compound is unknown. To facilitate the mechanism of action and preclinical studies of chrysomycin A, we developed a 10-step, scalable synthesis of the isolate and its two natural congeners polycarcin V and gilvocarcin V. The synthetic sequence was enabled by the implementation of two sequential C-H functionalization steps as well as a late-stage C-glycosylation. In addition, >10 g of the advanced synthetic intermediate has been prepared, which greatly facilitated the synthesis of 33 new analogues to date. The structure-activity relationship was subsequently delineated, leading to the identification of derivatives with superior potency against MDR-TB (MIC = 0.08 μg/mL). The more potent derivatives contained a modified carbohydrate residue which suggests that further optimization is additionally possible. The chemistry we report here establishes a platform for the development of a novel class of anti-TB agents active against drug-resistant pathogens.

From Pd(OAc)2 to Chiral Catalysts: The Discovery and Development of Bifunctional Mono-N-Protected Amino Acid Ligands for Diverse C-H Functionalization Reactions

The functionalization of unactivated carbon-hydrogen bonds is a transformative strategy for the rapid construction of molecular complexity given the ubiquitous presence of C-H bonds in organic molecules. It represents a powerful tool for accelerating the synthesis of natural products and bioactive compounds while reducing the environmental and economic costs of synthesis. At the same time, the ubiquity and strength of C-H bonds also present major challenges toward the realization of transformations that are both highly selective and efficient. The development of practical C-H functionalization reactions has thus remained a compelling yet elusive goal in organic chemistry for over a century.Specifically, the capability to form useful new C-C, C-N, C-O, and C-X bonds via direct C-H functionalization would have wide-ranging impacts in organic synthesis. Palladium is especially attractive as a catalyst for such C-H functionalizations because of the diverse reactivity of intermediate palladium-carbon bonds. Early efforts using cyclopalladation with Pd(OAc)₂ and related salts led to the development of many Pd-catalyzed C-H functionalization reactions. However, Pd(OAc)₂ and other simple Pd salts perform only racemic transformations, which prompted a long search for effective chiral catalysts dating back to the 1970s. Pd salts also have low reactivity with synthetically useful substrates. To address these issues, effective and reliable ligands capable of accelerating and improving the selectivity of Pd-catalyzed C-H functionalizations are needed.In this Account, we highlight the discovery and development of bifunctional mono-N-protected amino acid (MPAA) ligands, which make great strides toward addressing these two challenges. MPAAs enable numerous Pd(II)-catalyzed C(sp²)-H and C(sp³)-H functionalization reactions of synthetically relevant substrates under operationally practical conditions with excellent stereoselectivity when applicable. Mechanistic studies indicate that MPAAs operate as unique bifunctional ligands for C-H activation in which both the carboxylate and amide are coordinated to Pd. The N-acyl group plays an active role in the C-H cleavage step, greatly accelerating C-H activation. The rigid MPAA chelation also results in a predictable transfer of chiral information from a single chiral center on the ligand to the substrate and permits the development of a rational stereomodel to predict the stereochemical outcome of enantioselective reactions.We also describe the application of MPAA-enabled C-H functionalization in total synthesis and provide an outlook for future development in this area. We anticipate that MPAAs and related next-generation ligands will continue to stimulate development in the field of Pd-catalyzed C-H functionalization.

Radical α-addition involved electrooxidative [3 + 2] annulation of phenols and electron-deficient alkenes

An electrooxidative [3 + 2] annulation of phenols and electron-deficient alkenes for the synthesis of C3-functionalized 2-aryl-2,3-dihydrobenzofuran derivatives was achieved. The ring construction starts by a unique α-addition of carbon radicals derived from anodic oxidation of phenols to electron-deficient alkenes. The subsequent anodic oxidation of the resulting alkyl radical intermediates followed by trapping with the phenolic hydroxy group assembles the 2,3-dihydrobenzofuran core. Such a pathway enables the installation of various electrophilic functionalities including alkoxycarbonyl, alkylaminocarbonyl, trifluoromethyl, and cyano groups at the C-3 of the 2,3-dihydrobenzofuran framework, which is unattainable by other intermolecular reactions. The application of this method for a rapid synthesis of a bioactive natural product is demonstrated.

An electrooxidative [3 + 2] annulation between phenols and electron-deficient alkenes for the synthesis of C3-functionalized 2-aryl-2,3-dihydrobenzofuran derivatives is described.

Rh(III)-Catalyzed C–H Bond Activation for the Construction of Heterocycles with sp3-Carbon Centers

Rh(III)-catalyzed C–H activation features mild reaction conditions, good functional group tolerance, high reaction efficiency, and regioselectivity. Recently, it has attracted tremendous attention and has been employed to synthesize various heterocycles, such as indoles, isoquinolines, isoquinolones, pyrroles, pyridines, and polyheterocycles, which are important privileged structures in biological molecules, natural products, and agrochemicals. In this short review, we attempt to present an overview of recent advances in Rh(III)-mediated C–H bond activation to generate diverse heterocyclic scaffolds with sp3 carbon centers.

Total Synthesis of (-)-Salinosporamide A via a Late Stage C-H Insertion

The synthesis of (-)-salinosporamide A, a proteasome inhibitor, is described. The synthesis highlights the assembly of a densely decorated pyrrolidinone core via an aza-Payne/hydroamination sequence. Central to the success of the synthesis is a late-stage C-H insertion reaction to functionalize a sterically encumbered secondary carbon. The latter functionalization leads to an enabling transformation where most of the prototypical strategies failed.

Dialkyl Carbonates in the Green Synthesis of Heterocycles

This review focuses on the use of dialkyl carbonates (DACs) as green reagents and solvents for the synthesis of several 5- and 6-membered heterocycles including: tetrahydrofuran and furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines, and cyclic carbamates. Depending on the heterocycle investigated, the synthetic approach used was different. Tetrahydrofuran systems, pyrrolidines, indolines, isoindoline, and 1,4-dioxanes were synthesized using dimethyl carbonate (DMC) as sacrificial molecule (BAc2/BAl2 mechanism). Cyclic carbamates, namely 1,3-oxazin-2-ones, were prepared employing DACs as carbonylating agents, either by BAc2/BAl2 mechanism or through a double BAc2 mechanism. Piperidines were synthetized taking advantage of the anchimeric effect of a new family of dialkyl carbonates, i.e., mustard carbonates. Finally, in the case 5-hydroxymethylfurfural (HMF), DMC has been employed as efficient extracting solvent of this extensively investigated bio-based platform chemical from the reaction mixture. These synthetic approaches demonstrate, once again, the great versatility of DACs and their-yet to be fully explored-potential as green reagents and solvents in the synthesis of heterocycles.

Synthetic approaches to natural products containing 2,3-dihydrobenzofuran skeleton

This review describes the synthetic approaches to natural products containing the 2,3-dihydrobenzofuran (2,3-DHB) skeleton.

Recent applications of C-H functionalization in complex natural product synthesis

In this review, recent examples featuring C-H functionalization in the synthesis of complex natural products are discussed. A focus is given to the way in which C-H functionalization can influence the logical process of retrosynthesis, and the review is organized by the type and method of C-H functionalization.

Dynamic Kinetic Resolution for Construction of Three Transannular Stereocenters of Dihydrobenzofuranols

A handy and effective method was established to obtain the cis-2,3-dihydrobenzofuranols having three stereocenters, involving asymmetric transfer hydrogenation of benzofuranones via dynamic kinetic resolution. The general applicability of this method was examined with different benzofuran-3-(2 H)-ones, and stereoselectivities of 85-99% ee and up to 98/2 dr were obtained.

Nitrate-promoted Selective C-H Fluorination of Benzamides and Benzeneacetamides

A versatile and site-selective nitrate-promoted C-H bond fluorination using various weak coordinating amides as intrinsic directing groups was developed. Diverse tertiary and secondary amides underwent selective aromatic C-H bond fluorination, which features broad substrate scope, good regioselectivity, and mild conditions. Moreover, the late-stage C-H bond fluorination of the challenging benzeneacetamides via distal directing was reported for the first time.

Palladium(II)-Catalyzed Mono- and Bis-alkenylation of N-Acetyl-2-aminobiaryls through Regioselective C-H Bond Activation

We developed palladium-catalyzed oxidative coupling of olefins with N-acyl 2-aminobiaryls through a sequence of ortho C-H bond activation/alkene insertion/reductive elimination. Furthermore, we controlled the selectivity of mono- and bis-alkenylation products with the solvent effect. The developed protocol was promising for a broad substrate scope ranging from activated olefins with a wide variety of functional groups to unactivated olefins.

Formal total synthesis of salvianolic acid N

Salvianolic acid N was synthesized starting from 3,4-dimethoxybenzaldehyde in 11 steps and with an overall yield of 11%. The key reaction steps were the Wittig reaction for Z-stereoselectivity, the copper catalyzed intramolecular cyclization for seven membered ring skeleton, and the deprotected allylic group with Pd catalysis.

Synthesis of trans-disubstituted-2,3-dihydrobenzofurans by a formal [4 + 1] annulation between para-quinone methides and sulfonium salts

An efficient protocol for the synthesis of trans-disubstituted-2,3-dihydrobenzofurans through [4 + 1] annulation of para-quinone methides with sulfonium salts has been developed.

2-(1-Methylhydrazinyl)pyridine as a reductively removable directing group in a cobalt-catalyzed C(sp2)–H bond alkenylation/annulation cascade

A new application of 2-(1-methylhydrazinyl)pyridine as a reductively bidentate directing group to directing cobalt-catalyzed C(sp²)–H alkenylation/annulation to form isoquinoline backbones.