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Herein, we report visible-light induced C–O bond cleavage of vinyl-appended cyclic synthons via a Co(II)-photoredox dual catalytic approach operating at room temperature. This methodology exhibits a broad scope and is capable of accessing linear as well as branched allyl arenes simply by tuning the ring size of the cyclic motifs, in a mild and environmentally friendly protocol. Mechanistic studies unveil an interesting aspect of the reaction pathway involving a challenging homolytic cleavage of the Co(III)–O bond, 1,5-HAT of an unstable Co(II)-organometallic intermediate, and the key roles of O2 and the photocatalyst. The successful removal of the directing group further adds an important dimension to the methodology. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of the synthesis and modification of organic fluorophores, which are organic compounds that emit light when excited. It discusses various synthetic reactions used to create these fluorescent molecules, with a focus on transition-metal-catalyzed C–H activation reactions. The article categorizes recent C–H activation reactions and evaluates their advantages and limitations. This information is valuable for researchers and readers interested in the field of organic fluorophores. The document also includes biographical information about the authors, Dr. Tapasi Chand and Dr. Manmohan Kapur. [Extracted from the article]

Reported herein is an efficient and eco-friendly peri-selective monohydroxylation of naphthalene monoimides (NMIs) to access 4-hydroxy NMIs, which possess multidisciplinary applications. The key aspect of this method is the utilization of cobalt(II)-catalysis via a single electron transfer mechanism to achieve site-selective C(sp2)-hydroxylation. Transformation of the hydroxyl group into pseudohalides reveals its applications towards cross-coupling reactions. [ABSTRACT FROM AUTHOR]

Herein, we report an efficient synthetic strategy for an Fe(ii)-catalyzed site-selective ring opening of bicyclo[n.1.0]alkanols and their concomitant 1,6-conjugate addition to p-quinone methides. Access to tertiary carbon centers with appendaged carbocycles of distinct sizes and functional groups are achieved, under a substrate-controlled bond scission of the fused cyclopropanols. Synthetic derivatizations further enhance the utility of the protocol. [ABSTRACT FROM AUTHOR]

A site‐selective C(3)/C(4)‐alkylation of N‐pyridylisoquinolones is achieved by employing C−C bond activation of cyclopropanols under Ru(II)‐catalyzed/Cu(II)‐mediated conditions. The regioisomeric ratios of the products follow directly from the electronic nature of the cyclopropanols and isoquinolones used, with electron‐withdrawing groups yielding predominantly the C(3)‐alkylated products, whereas the electron‐donating groups primarily generate the C(4)‐alkylated isomers. Density functional theory calculations and detailed mechanistic investigations suggest the simultaneous existence of the singlet and triplet pathways for the C(3)‐ and C(4)‐product formation. Further transformations of the products evolve the utility of the methodology thereby yielding scaffolds of synthetic relevance. [ABSTRACT FROM AUTHOR]

The third position of cyclopentadienyl ring of a monosubstituted ferrocene has remained as an inaccessible chemical space for direct functionalization. Until recently, functionalizing the C(3)‐position while bypassing the predominantly active C(2)‐position is the most challenging task. Herein, we report a distal C−H functionalization of monosubstituted ferrocenes using an easily removable directing group with precise site‐selectivity, under a PdII/ mono‐N‐protected amino‐acid ligand catalytic system. The robust synthetic protocol leads to the synthesis of ferrocene 1,3‐derivatives with broad scope in olefins while functionalizing ferrocenyl methylamine in moderate to good yields via a highly strained ferrocene appended 12‐membered palladacycle intermediate. [ABSTRACT FROM AUTHOR]

We report herein, a modular, regioselective 1,3-oxyarylation of vinyl diazo esters via a Co-catalyzed C–H activation/carbene migratory insertion cascade. The transformation involves the formation of C–C and C–O bonds in a one-pot fashion and displays a broad substrate scope with respect to both, vinyl diazo esters as well as benzamides. The coupled products were subjected to hydrogenation to access elusive allyl alcohol scaffolds. Mechanistic investigations reveal interesting insights on the mode of transformation, involving C–H activation, carbene migratory insertion of the diazo compound followed by a radical addition as the key steps of the transformation. [ABSTRACT FROM AUTHOR]

Reported herein is a reactivity of propargyl alcohols as "Three‐Carbon Synthons" in a Rh(III)‐catalyzed C−H functionalization of acetanilides, leading to the synthesis of core structures of isocryptolepine, γ‐carbolines, dihydrochromeno[2,3‐b]indoles, and diindolylmethanes (DIM) derivatives. The transformation involves a rhodium(III)‐catalyzed C−H functionalization and heteroannulation to yield indoles followed by a cascade cyclization with both external and internal nucleophiles to afford diverse products. The role of the hydroxy group, the key function of the silver additive, the origin of the reverse regioselectivity and the rate‐determining step, are rationalized in conformity with the combination of experimental, noncovalent interaction analysis and DFT studies. This protocol is endowed with several salient features, including one‐pot multistep cascade approach, exclusive regioselectivity, good functional group tolerance and synthesis of variety of molecular frameworks. [ABSTRACT FROM AUTHOR]

The total synthesis of the 14‐membered resorcylic acid lactone neocosmosin A is described. The key step in the synthesis is the palladium‐catalyzed α‐arylation of TES‐enol ethers of enones. The employment of the α‐arylation approach to this class of resorcylic acid lactones is a new approach, which has the scope of being generalized into a unified approach for the synthesis of this class of natural products. [ABSTRACT FROM AUTHOR]

Herein, a de novo vinylogous reactivity of vinyl diazo esters in the C–H bond allylation of benzamides has been developed by coalescing cobalt and photoredox catalysis via C–H activation/allyl carbene migratory insertion. A close relationship between the high valent cobalt catalyst and the photocatalyst has been found to be crucial for this reactivity. The reaction uses oxygen as the sole oxidant and produces benign nitrogen as the only by-product. The reaction shows a good substrate scope with respect to both vinyl diazo esters and benzamides. The utility of the protocol is demonstrated through the late-stage functionalization of several bioactive molecules. [ABSTRACT FROM AUTHOR]

A one‐step Rh‐catalyzed site‐selective ortho‐C−H alkynylation of perylene as well as naphthalene mono‐ and diimides is reported. A single step regioselective access to ortho‐C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho‐functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization. [ABSTRACT FROM AUTHOR]

The dominant fungal-growth-promoting substance produced by the mycorrhiza helper bacterium Streptomyces strain AcH 505, auxofuran, is isolated and its effect on the levels of gene expression of Amanita muscaria is investigated. The characterization has provided the foundation for molecular analysis of the fungus-bacterium interaction in the ectomycorrhizal symbiosis between fly agaric and spruce.

A ruthenium-catalyzed oxidative coupling of vinylene carbonate with isoxazoles has been developed to achieve the direct C–H formylmethylation of a diverse array of arylisoxazoles utilizing the isoxazole ring as the directing group. A simple manipulation of the established reaction conditions leads to the formation of fused-anthranils. Importantly, the vinylene carbonate functions as both a formylmethyl cation equivalent through a decarboxylation process and an acetylene equivalent. Control experiments were conducted to elucidate a plausible mechanism. This methodology is expected to provide a facile and expeditious approach for the synthesis of formylmethyl isoxazoles and fused-anthranils. [ABSTRACT FROM AUTHOR]

The past decade has witnessed tremendous developments in transition‐metal‐catalyzed C−H bond activation and subsequent carbene migratory insertion reactions, thus assisting in the construction of diverse arene/heteroarene scaffolds. Various transition‐metal catalysts serve this purpose and provide efficient pathways for an easy access to substituted heterocycles. A brief introduction to metal‐carbenes has been provided along with key mechanistic pathways underlying the coupling reactions. The purpose of this review is to provide a concise knowledge about diverse directing group‐assisted coupling of varied arenes/heteroarenes and acceptor‐acceptor/donor‐acceptor diazo compounds. The review also highlights the synthesis of various carbocycles and fused heterocycles through diazo insertion pathways, via C−C, C−N and C−O bond forming reactions. The mechanism usually involves a C−H activation process, followed by diazo insertion leading to subsequent coupling. [ABSTRACT FROM AUTHOR]

Isoxazoles are an important class of heterocycles with nitrogen and oxygen in a 1,2‐relationship. They find wide applications in synthetic organic chemistry and are part of several drug molecules. Since the last two decades, great progress has been achieved in the synthesis and functionalization of isoxazoles, in which transition metal catalysis played a pivotal role towards achieving this goal. In particular, the transition metal (TM)‐mediated site‐selective functionalizations of isoxazoles which retain the pharmacologically and synthetically valuable isoxazole skeleton, are highly appealing. This comprehensive review is solely dedicated to the TM‐mediated functionalization of isoxazoles, wherein we have included isoxazoles as directing groups (DG) for TM‐catalyzed C−H functionalization reactions, TM‐catalyzed direct C−H functionalization, along with cross‐coupling reactions of isoxazoles, TM‐catalyzed annulation reactions of isoxazoles and finally ring‐opening reactions of isoxazoles under TM‐catalysis are also discussed. Also, incorporated are discussions on reaction designs, their advantages and limitations, mechanistic details and challenges that need to be addressed to inspire synthetic organic and medicinal chemists to explore new reaction arenas and make use of this key scaffold. [ABSTRACT FROM AUTHOR]

Over the last two decades, transition-metal catalyzed C–H functionalization of indoles has emerged as an area of extensive research and tremendous progress has been made in this regard. Early developments led to the positional-selective C–H functionalization at the C3 and C2-positions of indoles, based on the inherent reactivity of indoles and the application of Lewis-basic directing groups. Despite the challenges associated with lower accessibility of the C–H bonds on the benzenoid ring, considerable efforts have also been made in the development of elegant methodologies to enable site-selective C–H functionalization on the benzenoid moiety, at C4–C7 positions. This review summarises a wide range of useful transformations, including C–H arylation, alkenylation, alkynylation, acylation, nitration, borylation, annulations, and amidation with the aid of various transition-metal catalysts. [ABSTRACT FROM AUTHOR]

A tremendous upsurge has been seen in the recent decade for the proximal and remote functionalization of activated and unactivated substrates via palladium redox pathways. This feature article discusses some of the recent reports on direct as well as indirect C(sp3)–H functionalization via cross-coupling reactions under palladium catalysis. Activated substrates (possessing acidic C(sp3)–H) including enones, ketones, aldehydes, silylenol ethers, esters, silyl ketene acetals, amides, cyano, α-amino esters, and O-carbamates, capable of undergoing cross-coupling reactions at the α-, β-, γ-, δ- and ε-positions, will be discussed. To overcome the challenging task of achieving regioselectivity, a variety of innovative modifications have been reported. The reports of C–H activations based on directing group, and as native functionality have been illustrated at the β-, γ- and δ-positions. Substrates such as α-amino esters, carbonyls, carboxylic acids and their derivatives, afford site-selective C(sp3)–H functionalization via varied-sized reactive metallacycles and are a unique class of substrates whose C(sp3)–H functionalizations were earlier considered as very difficult. [ABSTRACT FROM AUTHOR]

An efficient ruthenium(II)‐ and copper(II)‐mediated, "one‐pot" synthesis of pyrroles has been reported. The reaction most probably proceeds via a reductive cleavage of isoxazoles. This protocol results in the synergistic formation of new C−C, C−N bonds, which leads to a simple and an efficient method for the synthesis of highly functionalized pyrroles from isoxazoles and acrylate esters. [ABSTRACT FROM AUTHOR]

A unique approach to achieve site‐selective C−H olefinations exclusively at the C‐3‐ or C‐8‐positions in the quinoline framework has been developed by catalyst control. Distal C(3)−H functionalization is achieved by using palladium catalysis, whereas proximal C(8)−H functionalization is obtained by employing ruthenium catalysis. Switching the site selectivity within a single substrate directly indicates two diverse pathways, which are operating under the palladium‐ and ruthenium‐catalyzed reaction conditions. [ABSTRACT FROM AUTHOR]

A simple and effective Pd(II)-catalyzed regioselective C(2)–H arylation of 6,5-fused heterocycles with dioxazolones as a masked ester surrogate under mild conditions is reported. The significance of the arylation is highlighted by the new reactivity demonstrated in dioxazolones via proximal C–H activation of the cyclic carbonate of the hydroxamic acid functionality under protic conditions. [ABSTRACT FROM AUTHOR]

A unique approach to achieve regioselective C(3)–H olefination of isoquinolines under ruthenium-catalyzed conditions has been developed. The acetyl group of N -acetyl-1,2-dihydroisoquinoline acts as a directing group for this C–H olefination strategy. Removal of the acetyl directing group by a simple method leads to a quick access to C-3 olefinated isoquinolines. The methodology is a very good alternative to the traditional Heck reaction and substrates with halogen substituents are very good candidates for the transformation. [ABSTRACT FROM AUTHOR]

A rare, ruthenium‐catalyzed, oxazolinlyl assisted C−H functionalization and three‐component cascade cyclization for the synthesis of isoquinolinones via a metal‐carbene migratory insertion is reported. The transformation is unique since it involves the formation of multiple bonds in one pot via C−H functionalization and ring opening of oxazolines. Detailed mechanistic investigations reveal interesting insights on the mode of transformation, involving reversible C−H activation, migratory insertion of the diazo compound and cascade cyclization as the key step of the transformation. [ABSTRACT FROM AUTHOR]

Abstract: Aryl halides are an indispensably important class of compounds owing to their role as precursors in the synthesis of organometallic reagents and nucleophilic substitution reactions. In addition, with the advent of cross‐coupling chemistry, the importance of aryl halides has increased tremendously, and they are therefore classified as the core building blocks in organic synthesis. With the recent advances in the area of transition‐metal‐catalyzed C−H functionalization, metal‐catalyzed C−H halogenation has emerged as a modern tool in organic synthesis. This focus review highlights the significant developments in the area of directed C−H halogenation reactions, particularly in the last two years. [ABSTRACT FROM AUTHOR]

Abstract: Electron‐deficient aromatic heterocycles, such as pyridine, quinoline, and isoquinoline, occupy a vast and rapidly expanding area of chemistry because of the obvious application of their derivatives in medicine, agriculture, polymers, and other fields. These heterocycles are rather poorly reactive towards electrophilic metalation by C−H activation and oxidative C−H activation mechanisms. The catalytic C−H functionalization of electron‐ deficient heterocycles remains a challenge for the synthetic chemistry community. This Focus Review highlights significant developments made in the area of transition‐metal‐catalyzed C−H functionalization of π‐deficient heterocycles. [ABSTRACT FROM AUTHOR]

Abstract: A mild and efficient C(sp2)−H nitration of 3‐substituted indoles, by using the economical and non‐toxic cobalt nitrate hexahydrate [Co(NO3)2⋅6 H2O] as a catalyst and tert‐butyl nitrite (TBN) as the nitro source, is reported. This approach provides a unique methodology involving a site‐selective C−N bond formation for preparation of C‐2 substituted nitro indoles. Utilization of the tBoc as the removable directing group enhances the synthetic utility of the method. [ABSTRACT FROM AUTHOR]

Site selectivity is an inherent challenge in C-H functionalization reactions. The most intensively sought-after approaches have involved the employment of Lewis-basic coordinating groups to direct a metal to a proximal site, in the process generating a metallacycle capable of further organometallic reactivity. In the recent years considerable effort has been directed towards the development of new transformations involving transition-metal-mediated C-H functionalization directed by weakly coordinating groups. This microreview focuses on the role and utility of amides and anilides in directed, proximal C-H bond functionalization reactions. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed, ortho-selective C-H halogenation methodology is reported herein. The highlight of the work is the highly selective C(sp²)-H functionalization of benzyl nitriles in the presence of activated C(sp³)-H bond, which results in good yields of the halogenated products with excellent regioselectivity. Along with benzyl nitriles, aryl Weinreb amides and anilides have been evaluated for the transformation using aprotic conditions. Mechanistic studies yield interesting aspects with respect to the pathway of the reaction and the directing group abilities. [ABSTRACT FROM AUTHOR]

A new class of Weinreb amides has been developed as directing groups for the ruthenium-catalysed regioselective oxidative C−H olefination. The new Weinreb amides successfully inhibit the N−O bond reductive cleavage usually associated with the cationic ruthenium system, thereby keeping intact the synthetic utility of Weinreb amides. Mechanistic studies reveal interesting aspects of the directing group capabilities of Weinreb amides when compared to simple amides of similar structures. [ABSTRACT FROM AUTHOR]

A new ruthenium-catalyzed, heteroatom-directed strategy for C-H allylation of indoles is described. The use of allyl alcohols as coupling partners as well as pyridine as the removable directing group is highlighted. This methodology provides access to C2-allylated indoles by utilizing a strategy that does not require prefunctionalization of either of the coupling partners. [ABSTRACT FROM AUTHOR]

The ruthenium-catalyzed Fujiwara-Moritani reaction (oxidative-Heck reaction) of Weinreb amides is reported herein. The reaction affords exclusively ortho-C−H olefination products, has excellent substrate scope and tolerates halogen functionalities, which increase the synthetic utility of the method. A variety of activated olefins as well as styrenes can be employed as coupling partners. [ABSTRACT FROM AUTHOR]