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The directed oxidative Heck coupling of Weinreb amides is studied in the presence of Ru/Ag-catalyst system. [ABSTRACT FROM AUTHOR]

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 O 2 and the photocatalyst. The successful removal of the directing group further adds an important dimension to the methodology.

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(sp 2 )-hydroxylation. Transformation of the hydroxyl group into pseudohalides reveals its applications towards cross-coupling reactions.

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., (© 2023 Wiley-VCH GmbH.)

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 Pd II / 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., (© 2023 Wiley-VCH Verlag GmbH.)

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., (© 2022 Wiley-VCH GmbH.)

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., (© 2022 Wiley-VCH GmbH.)

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., (© 2021 The Chemical Society of Japan & Wiley-VCH GmbH.)

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.

A mild and efficient C(sp 2 )-H nitration of 3-substituted indoles, by using the economical and non-toxic cobalt nitrate hexahydrate [Co(NO 3 ) 2 ⋅6 H 2 O] 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., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

[reaction: see text] A new approach to complex chiral diols and polyols is described utilizing a tandem hydroboration/Suzuki cross-coupling reaction. This method utilizes the versatility of a glycolate-derived chiral template.