Rh(III)-catalyzed selective mono- and dual-functionalization/cyclization of 1-aryl-5-aminopyrazoles with iodonium ylides

An efficient Rh(III)-catalyzed selective mono- and dual-C-H bond functionalization/cyclization with iodonium ylide as a single coupling partner was demonstrated, in which fused benzodiazepine skeletons were obtained in excellent yields. This method greatly improved an effective approach to dual C-H unsymmetrical functionalization.

Palladium-catalyzed interannular C-H amination of biaryl amines

A palladium-catalyzed interannular C-H amination of biaryl amines with O-benzoylhydroxylamines is reported. This reaction undergoes smoothly with operational practicality and good tolerance of functional groups, thereby providing a concise synthesis of 2,2'-diaminobiaryls. Moreover, the readily accessible scale-up synthesis and the ability to transform the products into structurally diverse N-containing heterocycles demonstrate the synthetic potential of this catalytic protocol.

Palladium-Catalyzed Sequential Three-Component Cross-Coupling to 1,3-Dienes: Employing Alkenes as Hydride and Alkenyl Donors

This report discloses a novel Pd-catalyzed sequential three-component multiple reaction of alkenes, bromoalkynes, and boronic acids using alkenes as hydride and alkenyl donors, leading to highly stereoselective assembly of (Z,E)-1,3-diene derivatives. Mechanistic studies demonstrate that the generation and reutilization of palladium hydride species are critical to the success of this transformation. In addition, the good functional group compatibility, late-stage modification, and investigation of photophysical properties of 1,3-diene products illustrate the synthetic value of this strategy.

Pro-oxidant response and accelerated ferroptosis caused by synergetic Au(I) release in hypercarbon-centered gold(I) cluster prodrugs

Medicinal applications of gold complexes have recently attracted attention due to their innovative antitumor mechanisms. In this work, two hypercoordinated carbon-centered gold clusters PAA4 and PAA5 are quantitatively synthesized by an intramolecular 6-exo-dig cyclization of polymetalated precursors. The on-bench and in vitro experimental studies demonstrate that the characteristic hypercarbon-tetragold(I) multi-center bonding in PAA4 and PAA5 not only guarantees their stability under common physiological conditions, but also facilitates a glutathione (GSH)-triggered prompt and synergetic release of active Au(I) ions in the GSH-overexpressed and acidic microenvironment of human bladder cancer EJ cells. The instantly massive release of coordination unsaturated Au(I) ions causes the efficient inhibition of thioredoxin reductases and then induces a rapid pro-oxidant response, consequently causing the occurrence of accelerated ferroptosis of EJ cells. As a result, these hypercarbon-centered gold(I) cluster prodrugs show high cytotoxicity to bladder cancer cell lines and thus exhibit a significant inhibition effect towards bladder tumors in vivo. Correlation of the synergetic domino dissociation of carbon-polymetal multi-center bonding in metal clusters with the accelerated ferroptosis of cancer cells provides a strategy for metallo-prodrugs and opens a broader prospect for the biological application of metal cluster compounds.

Construction of 2-Amino-2'-ketonyl Biaryls via Acid-Mediated Ring Opening of 9H-Fluoren-9-ols with Organic Azides

A direct cross-coupling between 9H-fluoren-9-ols and organic azides for the synthesis of steric hindered 2-amino-2'-ketonyl biaryls was reported. The reaction featured an acid-mediated azidation/ring-expansion/hydrolysis cascade, which formally realized the C-N bond coupling reaction via cleavage of a C-C single bond. This method was applicable to chiral helical structure to give bulky axially chiral biaryls with full stereospecificity.

Transition Metal Catalyzed Free-Amine (-NH2 ) Directed C-H Bond Activation and Functionalization for Biaryl Frameworks

Transition-metal-catalyzed direct transformation of inert C-H bond has revolutionized the arsenal of main-stream organic synthesis, providing a new upfront to forge structurally enriched and biologically relevant scaffolds in a step- and atom-economical way. Past decades have accounted for the major developments in this realm, proclaiming excellent site-selectivity by exploiting a variety of coordinating directing groups (DGs). Consideration of versatile, abundant, sp³ -hybridized free-amine (-NH₂ ) functionality for the same purpose has always been a formidable task owing to its innate reactivity. In recent years, free-amine functionality has emerged as a potent DG for a wide range of C-C and C-heteroatom bonds formations and annulation cascades. In this review article, we have discussed the advancements of free-amine directed C-H activation/functionalization reactions towards biaryl frameworks made within a decade (2012 to 2021).

Combined Dynamic Kinetic Resolution and C-H Functionalization for Facile Synthesis of Non-Biaryl-Atropisomer-Type Axially Chiral Organosilanes

Although asymmetric C-H functionalization has been available for the synthesis of structurally diverse molecules, catalytic dynamic kinetic resolution (DKR) approaches to change racemic stereogenic axes remain synthetic challenges in this field. Here, a concise palladium-catalyzed DKR was combined with C-H functionalization involving olefination and alkynylation for the highly efficient synthesis of non-biaryl-atropisomer-type (NBA) axially chiral oragnosilanes. The chemistry proceeded through two different and distinct DKR: first, an atroposelective C-H olefination or alkynylation produced axially chiral vinylsilanes or alkynylsilanes as a new family of non-biaryl atropisomers (NBA), and second, the extension of this DKR strategy to twofold o,o'-C-H functionalization led to the multifunctional axially chiral organosilicon compounds with up to >99 % ee.

Palladium-catalyzed sequential acylation/annulation of indoles with acyl chlorides using primary amine as the directing group

An efficient, palladium(ii)-catalyzed, C(sp²)–H acylation/annulation of indoles with acyl chlorides for the synthesis of substituted indolo[1,2-a]quinazolines is reported.

RhIII -Catalyzed Double Dehydrogenative Coupling of Free 1-Naphthylamines with α,β-Unsaturated Esters

The Rh^III -catalyzed, consecutive double C-H oxidative coupling of free 1-naphthylamine and α,β-unsaturated esters through C-H/C-H and C-H/N-H bonds is reported. The one step reaction leads to the formation of biologically important alkylidene-1,2-dihydrobenzo[cd]indoles scaffolds. This efficient process is much more synthetically convenient and useful than others because the starting materials, such as 1-naphthylamine derivatives are readily available and the free amine serves as a directing group.

Palladium catalysed C-H arylation of pyrenes: access to a new class of exfoliating agents for water-based graphene dispersions

A new and diverse family of pyrene derivatives was synthesised via palladium-catalysed C-H ortho-arylation of pyrene-1-carboxylic acid. The strategy affords easy access to a broad scope of 2-substituted and 1,2-disubstituted pyrenes. The C1-substituent can be easily transformed into carboxylic acid, iodide, alkynyl, aryl or alkyl functionalities. This approach gives access to arylated pyrene ammonium salts, which outperformed their non-arylated parent compound during aqueous Liquid Phase Exfoliation (LPE) of graphite and compare favourably to state-of-the-art sodium pyrene-1-sulfonate PS1. This allowed the production of concentrated and stable suspensions of graphene flakes in water.

Iridium-catalyzed, ligand-controlled directed alkynylation and alkenylation of arenes with terminal alkynes

We report iridium-catalyzed C–C formation between benzamides and terminal alkynes.

Ligand Promoted, Palladium-Catalyzed C(sp2)-H Arylation of Free Primary 2-Phenylethylamines

A mono- N-protected amino acid (MPAA) ligand promoted, Pd(II)-catalyzed C(sp²)-H arylation of free primary 2-phenylethylamines using the native NH₂ as the directing group has been achieved. This method is compatible with challenging simple primary 2-phenylethylamines bearing α-hydrogen atoms. Application of this protocol in the direct structure modification of the drug molecule amphetamine is also demonstrated.

Palladium-catalyzed regioselective C–H alkynylation of indoles with bromoalkynes in water

A palladium-catalyzed regioselective C(sp²)–H alkynylation between indoles and bromoalkynes in water has been developed, affording diverse functionalized 2-alkynylindoles in good yields.

Palladium-catalyzed regioselective C–H alkynylation of indoles with haloalkynes: access to functionalized 7-alkynylindoles

A palladium-catalyzed exclusively selective alkynylation of indoles has been reported, affording concise access to 7-alkynylindoles from readily available starting materials.

Pseudo-tetrahedral Rhodium and Iridium Complexes: Catalytic Synthesis of E-Enynes

The reactions of the rhodium(I) and iridium(I) complexes [M(PhBP₃ )(C₂ H₄ )(NCMe)] (PhBP₃ =PhB(CH₂ PPh₂ )₃ ^- ) with alkynes have resulted in the synthesis of a new family of pseudo-tetrahedral complexes, [M(PhBP₃ )(RC≡CR')] (M=Rh, Ir), which contain the alkyne as a four-electron donor. The reactions of these unusual compounds with two-electron donors (L=PMe₃ , CNtBu) produced a change in the "donicity" of the alkyne from a 4e^- to a 2e^- donor to give five-coordinate complexes. These were the final products with the iridium complexes, whereas further reactions took place with the rhodium complexes. In particular, C(sp)-H bond activation of the alkyne occurred leading to hydrido alkynyl complexes. This process is essential for the further reactivity of the alkynes, and if the alkyne itself was used as reagent, E-enyne complexes were obtained. As a consequence of this chemistry, we show that the complex [Rh(PhBP₃ )(C₂ H₄ )(NCMe)] is a very efficient pre-catalyst for the regioselective di- and trimerization of terminal alkynes to E-enynes and benzene derivatives, respectively. Interestingly, acetonitrile significantly enhanced the catalytic activity by facilitating the C(sp)-H bond activation step. A hydrometalation mechanism to account for these experimental observations is proposed.

Ruthenium nanoparticle catalyzed selective reductive amination of imine with aldehyde to access tertiary amines

Reductive amination is one of the most frequently used transformations in organic synthesis. Herein, we developed a novel ruthenium nanoparticle embedded ordered mesoporous carbon catalyst (Ru-OMC) and a new hydrosilylation process for the synthesis of tertiary amines. We present a direct reductive amination of imines (C[double bond, length as m-dash]N bond) with aldehydes (C[double bond, length as m-dash]O bond) using hydrosilane as the reducing reagent under mild conditions. Moreover, the Ru-OMC catalysts can be reused for up to 14 runs without noticeably losing activity.

Pd(ii)-Catalyzed gamma-C(sp3)–H alkynylation of amides: selective functionalization of R chains of amides R1C(O)NHR

The first example of palladium(ii)-catalyzed alkynylation of an unactivated gamma C(sp³)–H bond of alkyl amides (cyclic, linear, and amino acids) is reported.