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Organoborons have emerged as versatile building blocks in organic synthesis to achieve molecular diversity and as carboxylic acid bioisosteres with broad applicability in drug discovery. Traditionally, these compounds are prepared by the substitution of Grignard/lithium reagents with electrophilic boron species and Brown hydroboration. Recent developments have provided new routes for the efficient preparation of organoborons by applying reactions using chemical feedstocks with leaving groups. As compared to the previous methods that used organic halides (I, Br, and Cl), the direct borylation of less reactive C-Het and C-C bonds has become highly important to get efficiency and functional-group compatibility. This Review aims to provide a comprehensive overview of this topic, including (1) C-F bond borylation,(2) C-O bond borylation, (3) C-S bond borylation, (4) C-N bond borylation, and (5) C-C bond borylation. Considerable attention is given to the strategies and mechanisms involved. We expect that this Review will inspire chemists to discover more efficient transformations to expand this field. [ABSTRACT FROM AUTHOR]

The Rh-catalyzed, remote terminal hydroarylation of active olefins at the C7-position of indoles and the ortho-position of indolines and anilines with the appropriate choice of a N-PtBu2 directing group through long-range deconjugative isomerization has been reported. This transformation not only overcomes the conjugate rule of Michael acceptors but also controls the positional selectivity of indoles, representing a significant advancement in both alkene isomerization and the C-H alkylation of indoles. [ABSTRACT FROM AUTHOR]

Recent advances in transition metal-catalyzed selective C–H functionalization of indoles have garnered tremendous attention. Great efforts have been devoted to C2 and C3 arylation because of the inherent reactivity of the pyrrole ring. Until recently, elegant methods have been developed to enable selective direct arylation on the benzenoid moiety at C4, C5, C6, and C7. This review highlights the contributions made in benzenoid direct arylation of indoles and presents their potential in organic synthesis. [ABSTRACT FROM AUTHOR]

The first example of intermolecular olefination of cyclobutanone oximes with alkenes via selective C−C bond cleavage leading to the synthesis of nitriles in the presence of a cheap copper catalyst is reported. The procedure is distinguished by mild and safe reaction conditions that avoid ligand, oxidant, base, or toxic cyanide salt. A wide scope of cyclobutanones and olefin coupling components can be used without compromising efficiency and scalability. The alternative visible-light-driven photoredox process for this coupling reaction was also uncovered. [ABSTRACT FROM AUTHOR]

The first example of intermolecular olefination of cyclobutanone oximes with alkenes via selective C−C bond cleavage leading to the synthesis of nitriles in the presence of a cheap copper catalyst is reported. The procedure is distinguished by mild and safe reaction conditions that avoid ligand, oxidant, base, or toxic cyanide salt. A wide scope of cyclobutanones and olefin coupling components can be used without compromising efficiency and scalability. The alternative visible-light-driven photoredox process for this coupling reaction was also uncovered. [ABSTRACT FROM AUTHOR]

An exclusive catalytic C4-selective fluoroalkylation of indoles with highly active (1H, 1H-perfluoroalkyl)mesityliodonium triflate has been described. The key to its high regioselectivity is the appropriate choice of an easily accessible, cheap and removable directing group at the C3 position in the presence of a Pd(OAc)2 catalyst. Besides indole fluoroalkylation, the application of this strategy in other heteroarenes such as benzo[b]thiophene is also described. [ABSTRACT FROM AUTHOR]

In the past decade, transition-metal-catalyzed C-H activations have been very popular in the research field of organometallic chemistry, and have been considered as efficient and convenient strategies to afford complex natural products, functional advanced materials, fluorescent compounds, and pharmaceutical compounds. In this account, we begin with a brief introduction to the development of transition-metal-catalyzed C-H activation, especially the development of transition-metal-catalyzed chelation-assisted C-H activation. Then, a more detailed discussion is directed towards our recent studies on the transition-metal-catalyzed chelation-assisted oxidative C-H/C-H functionalization of aromatic substrates bearing directing functional groups. [ABSTRACT FROM AUTHOR]

Fishing for complements! There is an alternative to the useful Fischer indole synthesis. The new method utilizes the same retrosynthetic disconnection but is based on a RhIII‐catalyzed directed CH activation step and a successive coupling with alkynes. [ABSTRACT FROM AUTHOR]

Fischen nach Komplementen! Eine Alternative zu der nützlichen Fischer ‐ Indolsynthese wird vorgestellt. Während die neue Methode die gleichen retrosynthetischen Schnitte nutzt, basiert sie auf einem RhIII ‐ katalysierten dirigierten C ‐ H ‐ Aktivierungsschritt und einer sukzessiven Kupplung mit Alkinen. [ABSTRACT FROM AUTHOR]

Abstract: A Pd(II)-catalyzed aerobic oxidative approach to 2,3-dihydro-1H-pyrrolo[1,2-a]indoles from simple N-alkynyl anilines through tandem intramolecular hydroamination and aryl C–H activation process has been developed. Molecular oxygen was used as the sole oxidant to recycle the Pd-catalysis. This protocol is attractive due to the available starting materials and the valuable products. [Copyright &y& Elsevier]

A rhodium(III)-catalyzed direct dehydrogenative annulation of benzamides with alkynes through chelating-assisted CH activation has been developed. Naphthylamide and isoquinolinone derivatives can be chemoselectively obtained by this protocol. [ABSTRACT FROM AUTHOR]

A new InCl3-catalyzed addition reaction of 1,3-dicarbonyl compounds to various alkenes proceeded in good yields and can be carried out in air, which provided an easy and practical procedure for carbon-carbon bond formation. [ABSTRACT FROM AUTHOR]

Efficient Rh(iii)-catalyzed C–H activation of different classes of (hetero)arenes such as 2-phenylpyridine, indoles, aryl ketones and acetanilide and their dehydrogenative cross-coupling with allylic alcohols are described. Several important skeletons such as β-aryl aldehydes and ketones, 2-acetylindenes, 3,4-dihydro-1H-quinolin-2-one and quinoline could be produced using this protocol. [ABSTRACT FROM AUTHOR]

The article presents a scientific method to obtain synthesis of fluorenones through quaternary ammonium salt promoted intramolecular dehydrogenative arylation of aldehydes. Chemical equations and reactions for gram-scale synthesis, xanthone synthesis, and bianthronyl synthesis are given in the article.

Chiral organoboronates have played a critical role in organic chemistry and in the development of materials science and pharmaceuticals. Much effort has been devoted to exploring synthetic methodologies for the preparation of these compounds during the past few decades. Among the known methods, asymmetric catalysis has emerged as a practical and highly efficient strategy for their straightforward preparation, and recent years have witnessed remarkable advances in this respect. Approaches such as asymmetric borylative addition, asymmetric allylic borylation and stereospecific cross-coupling borylation, have been extensively explored and well established employing transition-metal catalysis with a chiral ligand. This review provides a comprehensive overview of transition metal-catalysed asymmetric borylation processes to construct carbon–boron, carbon–carbon, and other carbon–heteroatom bonds. It summarises a range of recent achievements in this area of research, with considerable attention devoted to the reaction modes and the mechanisms involved. [ABSTRACT FROM AUTHOR]

Atropisomeric phosphines hold considerable significance in asymmetric catalysis, yet their synthesis presents a formidable challenge owing to intricate multistep procedures. In this context, a groundbreaking methodology has been presented for their preparation. This innovative approach entails an atroposelective rhodium‐catalyzed C−H activation employing aryl and heteroaryl halides, chelated by a P(III) center. The essence of this strategy lies in its ability to directly construct chiral phosphine ligands in a single step, thereby exhibiting exceptional efficiency in terms of atom and redox economy. Illustrative examples serve to demonstrate the immense potential of in situ‐formed ligands in asymmetric catalysis. Mechanistic experiments have further provided invaluable insights into this transformation. [ABSTRACT FROM AUTHOR]

Atropisomeric phosphines hold considerable significance in asymmetric catalysis, yet their synthesis presents a formidable challenge owing to intricate multistep procedures. In this context, a groundbreaking methodology has been presented for their preparation. This innovative approach entails an atroposelective rhodium‐catalyzed C−H activation employing aryl and heteroaryl halides, chelated by a P(III) center. The essence of this strategy lies in its ability to directly construct chiral phosphine ligands in a single step, thereby exhibiting exceptional efficiency in terms of atom and redox economy. Illustrative examples serve to demonstrate the immense potential of in situ‐formed ligands in asymmetric catalysis. Mechanistic experiments have further provided invaluable insights into this transformation. [ABSTRACT FROM AUTHOR]

The site-selective C–H bond functionalization of heteroarenes can eventually provide chemists with great techniques for editing and building complex molecular scaffolds. During the past decade, benzo-fused N-heterocycles such as indoles and quinolines have been among the most widely investigated organic templates. Early developments have led to site-selective C–H bond functionalization on the pyrrole and pyridine cores of indoles and quinolines; however, C–H functionalization on the benzenoid ring has remained a great challenge in catalysis. In this review, we elaborate on recent developments in the highly challenging functionalization of C–H bonds on the less-reactive benzenoid core of indoles and quinolines. These findings are mainly described as selective directing group assisted strategies, remote C–H functionalization techniques and their reaction mechanisms. The underlying principle in each strategy is elucidated, which aims to facilitate the design of a more advanced structure of heterocycles based on bioactive molecules, synthetic drugs, and material aspects. Moreover, the challenges and perspectives for catalytic C–H functionalization to access the arene backbone of indoles and quinolines are also proposed in the conclusion section. [ABSTRACT FROM AUTHOR]

Performing asymmetric cross‐coupling reactions between propargylic electrophiles and aryl nucleophiles is a well‐established method to build enantioenriched benzylic alkynes. Here, a catalytic enantioselective propargyl‐aryl cross‐coupling between two electrophiles was achieved for the first time in a stereoconvergent manner. Propargylic chlorides were treated with aryl iodides as well as heteroaryl iodides in the presence of a chiral nickel complex, and manganese metal was used as a stoichiometric reductant, allowing for the construction of a propargyl C‐aryl bond under mild conditions. An alternative dual nickel/photoredox catalytic protocol was also developed for this cross‐electrophile coupling in the absence of a metal reductant. The potential utility of this conversion is demonstrated in the facile construction of stereoenriched bioactive molecule derivatives and medicinal compounds based on the diversity of acetylenic chemistry. Detailed experimental studies have revealed the key mechanistic features of this transformation. [ABSTRACT FROM AUTHOR]

Performing asymmetric cross‐coupling reactions between propargylic electrophiles and aryl nucleophiles is a well‐established method to build enantioenriched benzylic alkynes. Here, a catalytic enantioselective propargyl‐aryl cross‐coupling between two electrophiles was achieved for the first time in a stereoconvergent manner. Propargylic chlorides were treated with aryl iodides as well as heteroaryl iodides in the presence of a chiral nickel complex, and manganese metal was used as a stoichiometric reductant, allowing for the construction of a propargyl C‐aryl bond under mild conditions. An alternative dual nickel/photoredox catalytic protocol was also developed for this cross‐electrophile coupling in the absence of a metal reductant. The potential utility of this conversion is demonstrated in the facile construction of stereoenriched bioactive molecule derivatives and medicinal compounds based on the diversity of acetylenic chemistry. Detailed experimental studies have revealed the key mechanistic features of this transformation. [ABSTRACT FROM AUTHOR]

[17] In this context, the development of efficient and mild methods for indole borylation has attracted increasing attention for research on the preparation of complex indoles. Although the use of a 1-adamantanoyl group can provide the desired indole C-H borylation products with high reactivity and selectivity, removing the directing group requires additional steps (Figure 4). Keywords: C-H bond activation; borylation; indoles; BBr 3; site selectivity; metal-free reaction EN C-H bond activation borylation indoles BBr 3 site selectivity metal-free reaction 2220 2226 7 10/31/23 20231127 NES 231127 Graph The indole ring system is one the most common heterocycles, present in many natural products and pharmaceuticals. [22] C2-Borylated indoles are versatile synthetic intermediates used to build 2,3-disubstituted indole skeletons as key intermediates in total syntheses of natural products and pharmaceuticals (Figure 1 A). [Extracted from the article]

Metal‐catalyzed C−H activation strategies provide an efficient approach for synthesis by minimizing atom, step, and redox economy. Developing milder, greener, and more effective protocols for these strategies is always highly desirable to the scientific community. In this study, the utilization of a single rhodium complex enabled the visible‐light‐induced late‐stage C−H activation of biaryl‐type phosphines with alkynyl bromides, employing inherent phosphorus atoms as directing groups. This chemistry combines P(III)‐directed C−H activation with visible light photocatalysis, under exogenous photosensitizer‐free conditions, offering a unique platform for ligand design and preparation. Furthermore, this study also explores the asymmetric catalysis and coordination chemistry of the resulting P‐alkyne hybrid ligands with specific transition metals. Experimental results and density functional theory calculations demonstrate the mechanistic intricacies of this transformation. [ABSTRACT FROM AUTHOR]

Metal‐catalyzed C−H activation strategies provide an efficient approach for synthesis by minimizing atom, step, and redox economy. Developing milder, greener, and more effective protocols for these strategies is always highly desirable to the scientific community. In this study, the utilization of a single rhodium complex enabled the visible‐light‐induced late‐stage C−H activation of biaryl‐type phosphines with alkynyl bromides, employing inherent phosphorus atoms as directing groups. This chemistry combines P(III)‐directed C−H activation with visible light photocatalysis, under exogenous photosensitizer‐free conditions, offering a unique platform for ligand design and preparation. Furthermore, this study also explores the asymmetric catalysis and coordination chemistry of the resulting P‐alkyne hybrid ligands with specific transition metals. Experimental results and density functional theory calculations demonstrate the mechanistic intricacies of this transformation. [ABSTRACT FROM AUTHOR]

An efficient method for photocatalytic perfluoroalkylation of vinyl‐substituted all‐carbon quaternary centers involving 1,2‐aryl migration has been developed. The rearrangement reactions use fac‐Ir(ppy)3, visible light and commercially available fluoroalkyl halides and can generate valuable multisubstituted perfluoroalkylated compounds in a single step that would be challenging to prepare by other methods. Mechanistically, the photoinduced alkyl radical addition to an alkene leads to the migration of a vicinal aryl substituent from its adjacent all‐carbon quaternary center with the concomitant generation of a C‐radical bearing two electron‐withdrawing groups that is further reduced by a hydrogen donor to complete the domino sequence. [ABSTRACT FROM AUTHOR]

An efficient method for photocatalytic perfluoroalkylation of vinyl‐substituted all‐carbon quaternary centers involving 1,2‐aryl migration has been developed. The rearrangement reactions use fac‐Ir(ppy)3, visible light and commercially available fluoroalkyl halides and can generate valuable multisubstituted perfluoroalkylated compounds in a single step that would be challenging to prepare by other methods. Mechanistically, the photoinduced alkyl radical addition to an alkene leads to the migration of a vicinal aryl substituent from its adjacent all‐carbon quaternary center with the concomitant generation of a C‐radical bearing two electron‐withdrawing groups that is further reduced by a hydrogen donor to complete the domino sequence. [ABSTRACT FROM AUTHOR]

Enamides, functional derivatives of enamines, play a significant role as synthetic targets. However, the stereoselective synthesis of these molecules has posed a longstanding challenge in organic chemistry, particularly for acyclic enamides that are less thermodynamically stable. In this study, we present a general strategy for constructing β‐borylenamides by C−H borylation, which provides a versatile platform for generating the stereodefined enamides. Our approach involves the utilization of metalloid borenium cation, generated through the reaction of BBr3 and enamides in the presence of two different additives, avoiding any exogenous catalyst. Importantly, the stereoconvergent nature of this methodology allows for the use of starting materials with mixed E/Z configurations, thus highlighting the unique advantage of this chemistry. Mechanistic investigations have shed light on the pivotal roles played by the two additives, the reactive boron species, and the phenomenon of stereoconvergence. [ABSTRACT FROM AUTHOR]

Enamides, functional derivatives of enamines, play a significant role as synthetic targets. However, the stereoselective synthesis of these molecules has posed a longstanding challenge in organic chemistry, particularly for acyclic enamides that are less thermodynamically stable. In this study, we present a general strategy for constructing β‐borylenamides by C−H borylation, which provides a versatile platform for generating the stereodefined enamides. Our approach involves the utilization of metalloid borenium cation, generated through the reaction of BBr3 and enamides in the presence of two different additives, avoiding any exogenous catalyst. Importantly, the stereoconvergent nature of this methodology allows for the use of starting materials with mixed E/Z configurations, thus highlighting the unique advantage of this chemistry. Mechanistic investigations have shed light on the pivotal roles played by the two additives, the reactive boron species, and the phenomenon of stereoconvergence. [ABSTRACT FROM AUTHOR]

A novel structural reorganization of cycloketoxime esters beyond the traditional Beckmann rearrangement process has been established to build cyano‐containing ketones in the presence of photocatalyst. This novel transformation is remarkable with selective C—C bond cleavage and an oxidation process enabled by DMSO used as the solvent, oxidant, and oxygen source avoiding acid, base and toxic cyanide salts as the cyano source. Further applications in late‐stage modification of complex and chiral molecules have also been reported. A SET‐induced strategy has been established for C—C bond cleavage and oxidation sequence of cycloketoxime esters in the presence of photocatalyst. The protocol is distinguished by mild and safe reaction conditions that avoid peroxide, acid, base and toxic cyanide salts. [ABSTRACT FROM AUTHOR]

Review: [40 refs. [ABSTRACT FROM AUTHOR]

Transition‐metal‐catalyzed enantioselective addition of aryl organometallic reagents to imines has emerged as one of the most powerful tools for the formation of optically active diarylmethylamines. Here, we report the first asymmetric reductive (hetero)arylations of imines using aryl and heteroaryl halides enabled by a chiral cobalt‐bisphosphine catalyst. This approach shows good functional group compatibility and complements the reported strategy without use of organometallic reagents. Mechanistic investigations supported that aryl‐cobalt, instead of an arylzinc reagent, was formed in situ in this reductive aryl‐addition event. [ABSTRACT FROM AUTHOR]

Transition‐metal‐catalyzed enantioselective addition of aryl organometallic reagents to imines has emerged as one of the most powerful tools for the formation of optically active diarylmethylamines. Here, we report the first asymmetric reductive (hetero)arylations of imines using aryl and heteroaryl halides enabled by a chiral cobalt‐bisphosphine catalyst. This approach shows good functional group compatibility and complements the reported strategy without use of organometallic reagents. Mechanistic investigations supported that aryl‐cobalt, instead of an arylzinc reagent, was formed in situ in this reductive aryl‐addition event. [ABSTRACT FROM AUTHOR]

leading to a variety of fused multicyclic lactams of biological interest [ABSTRACT FROM AUTHOR]

This reaction yields unprotected indoles from 2-acetyl-1-arylhydrazines and alkynes without the need for an external oxidant. [ABSTRACT FROM AUTHOR]

This is the first Rh-catalyzed method for the synthesis of isoquinoline and pyridine N-oxides with an arylic or vinylic C-H activation as cyclization-initiating step. [ABSTRACT FROM AUTHOR]

The dehydrogenative cross-coupling of indoles (I) and 2-phenylpyridine (IV) with allylic alcohols (II) affords β-aryl carbonyl compounds as sole products. [ABSTRACT FROM AUTHOR]

A novel synthesis of azepinone derivatives by using a Rh-catalyzed intramolecular annulation reaction of N-substituted benzamides and α,β-unsaturated aldehydes and ketones is developed. [ABSTRACT FROM AUTHOR]

Optimized conditions allow the selective preparation of pyrroloindole derivatives (II) with the exception that halo-substituted substrates (III) give pyrroles (V) as side products. [ABSTRACT FROM AUTHOR]

The mild cyclization of imines to various pyrrole structures uses molecular oxygen as the sole stoichiometric oxidant. [ABSTRACT FROM AUTHOR]

With the aim to obtain biologically interesting substances, fluorenones (II), (IV), (VI)/(VII) and related compounds such as (IX), and (XI)/(XII) are prepared via an intramolecular oxidative acylation process. [ABSTRACT FROM AUTHOR]

Depending on the reaction conditions this method can be used to synthesize naphthalene derivatives (III) as well as benzo[h]isoquinoline derivatives (VI). [ABSTRACT FROM AUTHOR]

Review: 19 refs. [ABSTRACT FROM AUTHOR]

The title reaction complements the Heck reaction on carbonyl substrates and provides substrates like aurones, e.g. (III), flavone (XVI), flavanone (XVII), and 2′-hydroxychalcones, e.g. (XIV), from readily available starting materials. [ABSTRACT FROM AUTHOR]