Mizoroki-Heck Reaction of Unstrained Aryl Ketones via Ligand-Promoted C-C Bond Olefination

Ring expansion of 3-hydroxyoxindoles to 4-quinolones via palladium-catalyzed C-C(acyl) bond cleavage

We report herein the construction of 4-quinolones via palladium-catalyzed regioselective β-acyl elimination of 3-hydroxyoxindoles and a subsequent Camps cyclization process. This protocol is highly efficient and various 4-quinolone derivatives are obtained in high yields. The construction of the core skeleton of the 4-quinolone antibiotics demonstrated the synthetic utility of this method.

Light-Driven Photocatalyst-Free Synthesis of β, δ-Functionalized Ketones from Aldehydes

The synthesis of ketones has been a long focus of chemistry research, on account of its unique reactivity. Herein, we report a simple light-driven photocatalyst-free synthesis of β, δ-functionalized ketones from aldehydes, using inexpensive and commercially abundant feedstock chemicals. This reaction is enabled by the direct acyl radical generation via hydrogen atom transfer and the subsequent radical addition process, avoiding the need for prefunctionalized substrates and organometallic reagent.

Palladium-Catalyzed Deuteration of Arylketone Oxime Ethers

We report herein the development of palladium-catalyzed deacylative deuteration of arylketone oxime ethers. This protocol features excellent functional group tolerance, heterocyclic compatibility, and high deuterium incorporation levels. Regioselective deuteration of some biologically important drugs and natural products are showcased via Friedel-Crafts acylation and subsequent deacylative deuteration. Vicinal meta-C-H bond functionalization (including fluorination, arylation, and alkylation) and para-C-H bond deuteration of electro-rich arenes are realized by using the ketone as both directing group and leaving group, which is distinct from aryl halide in conventional dehalogenative deuteration.

Carbon-Carbon Bond Cleavage for Late-Stage Functionalization

Late-stage functionalization (LSF) introduces functional group or structural modification at the final stage of the synthesis of natural products, drugs, and complex compounds. It is anticipated that late-stage functionalization would improve drug discovery's effectiveness and efficiency and hasten the creation of various chemical libraries. Consequently, late-stage functionalization of natural products is a productive technique to produce natural product derivatives, which significantly impacts chemical biology and drug development. Carbon-carbon bonds make up the fundamental framework of organic molecules. Compared with the carbon-carbon bond construction, the carbon-carbon bond activation can directly enable molecular editing (deletion, insertion, or modification of atoms or groups of atoms) and provide a more efficient and accurate synthetic strategy. However, the efficient and selective activation of unstrained carbon-carbon bonds is still one of the most challenging projects in organic synthesis. This review encompasses the strategies employed in recent years for carbon-carbon bond cleavage by explicitly focusing on their applicability in late-stage functionalization. This review expands the current discourse on carbon-carbon bond cleavage in late-stage functionalization reactions by providing a comprehensive overview of the selective cleavage of various types of carbon-carbon bonds. This includes C-C(sp), C-C(sp2), and C-C(sp3) single bonds; carbon-carbon double bonds; and carbon-carbon triple bonds, with a focus on catalysis by transition metals or organocatalysts. Additionally, specific topics, such as ring-opening processes involving carbon-carbon bond cleavage in three-, four-, five-, and six-membered rings, are discussed, and exemplar applications of these techniques are showcased in the context of complex bioactive molecules or drug discovery. This review aims to shed light on recent advancements in the field and propose potential avenues for future research in the realm of late-stage carbon-carbon bond functionalization.

Immobilization of Trifluoromethyl-Substituted Pyridine-Oxazoline Ligand and Its Application in Asymmetric Continuous Flow Synthesis of Benzosultams

This study presents an improved synthetic route to ligand (S)-4-(tert-butyl)-2-(5-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole and its application as a highly active and enantioselective catalyst in the addition of arylboronic acids to cyclic N-sulfonylketimines. Immobilization of such a ligand was achieved using a commercially available starting material and a PS-PEG TentaGel S NH2 support, resulting in a stable heterogeneous catalyst. Although the anchored catalyst exhibited a slight reduction in enantioselectivity and a 4-fold decrease in reaction rate, it displayed remarkable stability, enabling 10 consecutive reaction cycles. Furthermore, the successful transition to a continuous flow system demonstrated even higher turnover numbers compared to batch arrangements. These findings provide valuable insights into the development of efficient flow reactors for continuous synthesis of benzosultams, further advancing the field of asymmetric catalysis.

A New Pathway for the Synthesis of Ketones from Aldehydes and Sulfonylhydrazones: Is Diazo the Key Intermediate?

A new pathway via a cyclic intermediate for the synthesis of ketones from aldehydes and sulfonylhydrazone derivatives under basic conditions is proposed. Several control experiments were performed along with analysis of the mass spectra and in-situ IR spectra of the reaction mixture. Inspired by the new mechanism, an efficient and scalable method for homologation of aldehydes to ketones was developed. A wide variety of target ketones were obtained in yields of 42-95 % by simply heating the 3-(trifluoromethyl)benzene sulfonylhydrazones (3-(Tfsyl)hydrazone) for 2 h at 110 °C with aldehydes and with K2 CO3 and DMSO as base and solvent, respectively.

Construction of polysubstituted pentafulvenes via palladium-catalyzed deacetylation of enones

Herein, we report an efficient synthetic method for polysubstituted pentafulvenes via palladium-catalyzed deacetylative [2+2+1] annulation of enones with alkynes. Aryl-, alkenyl-, and alkyl-substituted α,β-enones were suitable substrates, affording the pentafulvene products in moderate to good yields. This protocol shows excellent compatibility with sensitive halides, free hydroxyl groups, and heterocycles. One-pot gram-scale synthesis and further applications in the late-stage modification of natural products demonstrate the synthetic utility of this method.

Merging the Norrish type I reaction and transition metal catalysis: photo- and Rh-promoted borylation of C-C σ-bonds of aryl ketones

Synthesis of arylboronates via borylation of C-C σ-bonds of aryl ketones was achieved by the combined use of photoenergy and a Rh catalyst. The cooperative system enables α-cleavage of photoexcited ketones to generate aroyl radicals via the Norrish type I reaction, which are successively decarbonylated and borylated with the rhodium catalyst. This work establishes a new catalytic cycle merging the Norrish type I reaction and Rh catalysis and demonstrates the new synthetic utility of aryl ketones as aryl sources for intermolecular arylation reactions.

Rh(III)-catalyzed C-H/C-C bond annulation of enaminones with iodonium ylides to form isocoumarins

A straightforward approach to synthesise isocoumarins via Rh(III)-catalyzed C-H/C-C bond activation/annulation cascade of enaminones and iodonium ylides has been explored. The established protocol is characterized by an exceedingly simple reaction system, high regioselectivity and good functional group tolerance. Moreover, this strategy may provide a new route to cleavage of the C(sp²)-C(O) bond of unstrained ketones.

Construction of C(sp2)-Si Bonds via Ligand-Promoted C-C Bonds Cleavage of Unstrained Ketones

Herein, we report an efficient palladium-catalyzed silylation of aryl and alkenyl ketones via C-C bond cleavage and C-Si bond formation. This protocol features high efficiency and broad substrate scope. Further applications in the late-stage diversification of biologically important molecules demonstrate the synthetic utility of this method.

Homologation of aryl ketones to long-chain ketones and aldehydes via C-C bond cleavage

Transition metal-catalyzed C-C bond cleavage is a powerful tool for the reconstruction of a molecular skeleton. We report herein the multi-carbon homologation of aryl ketones to long-chain ketones and aldehydes via ligand-promoted Ar-C(O) bond cleavage and subsequent cross coupling with alkenols. Various (hetero)aryl ketones are compatible in the reaction, affording the corresponding products wtih good to excellent yields with high regioselectivity. Further applications in the late-stage diversification of biologically important molecules demonstrate the synthetic utility of this protocol. Mechanistic studies indicate that the ligand plays an important role in both C-C bond cleavage and the asymmetric migration-insertion process.

An electron-deficient MOF as an efficient electron-transfer catalyst for selective oxidative carbon-carbon coupling of 2,6-di-tert-butylphenol

Naphthalene diimides (NDIs), a type of electron-deficient dye molecule with high quadrupole moment and excellent redox activity, have been utilized in various fields, such as energy transfer, chemical sensing, anion transport, and photo-/electrochromic materials. In this study, an electron-deficient metal-organic framework with one-dimensional channels, Eu₂(BBNDI)₃(DMF)₂ (MOF 1) (H₂BBNDI = N,N'-bis(3-benzoic acid)naphthalene diimide), was successfully constructed based on the naphthalene diimide derivative. Because of the generation of NDI radicals by electron transfer between components, this material exhibits fast-responsive reversible photochromic properties. Moreover, it shows high efficiency and selective oxidation of 2,6-di-tert-butylphenol to its quinone derivative, aldehyde, and dimeric or trimeric phenol derivative by controlling the reaction conditions.

Palladium-Catalyzed Alkynylation of Enones with Alkynylsilanes via C-C Bond Activation

We report herein the synthesis of 1,3-enynes via palladium-catalyzed cross-coupling between enone derivatives and alkynylsilanes. The employment of an appropriate pyridine-oxazoline ligand is the key to the C-C cleavage and the high E/Z stereoselectivity. This protocol features broad substrate scope and wide functional-group tolerance, affording the desired products in moderate-to-good yields. Late-stage diversification of natural product β-ionone further demonstrated the synthetic utility of this protocol.

2-Pyridinylmethyl borrowing: base-promoted C-alkylation of (pyridin-2-yl)-methyl alcohols with ketones via cleavage of unstrained C(sp3)–C(sp3) bonds

2-Pyridinylmethyl Borrowing: Transition-metal-free 2-pyridinylmethyl borrowing C-alkylation of alcohols access to ketones is developed. This unstrained C(sp3)–C(sp3) bonds cleavage of unactivated alcohols avoids the use of transition metals.

Arylketones as Aryl Donors in Palladium-Catalyzed Suzuki-Miyaura Couplings

Herein, we report the arylation, alkylation, and alkenylation of aryl ketones via a palladium-catalyzed Suzuki-Miyaura cross-coupling reaction. The use of the pyridine-oxazoline ligand is the key to the cleavage of the unstrained C-C bond. The late-stage arylation of aryl ketones derived from drugs and natural products demonstrated the synthetic utility of this protocol.

C3-Arylation of indoles with aryl ketones via C-C/C-H activations

C3-Arylation of indoles with aryl ketones is accomplished via palladium-catalyzed ligand-promoted Ar-C(O) cleavage and subsequent C-H arylation of indole. Various (hetero)aryl ketones are compatible in this reaction, affording the corresponding 3-arylindoles in moderate to good yields. Further introduction of an indole moiety into the natural products desoxyestrone and evodiamine demonstrate the synthetic utility of this protocol.