A general strategy for synthesis of heterocyclic hemiketal-containing α,β-unsaturated ketones has been established. Using the environmentally sound and readily available reagents water and thiourea applied to ynediones, a series of sensitive hemiketals of 3(2 H)-furanones and 3(2 H)-thienones were constructed under mild conditions. Both of the reaction conditions are compatible with a diverse range of functional groups. Isotopic labeling, tautomerism, and GC-MS tracking methods were used to reveal the mechanisms.

Copper-catalyzed, aerobic, oxidative, C3-dicarbonylation of indoles has been realized directly from α-hydroxyketones, which serve as an efficient dicarbonylative reagent under mild conditions. The method is widely compatibility with various functional groups, offering a straightforward means to produce different heterocycle-substituted quinoxalines in excellent yields. These diverse fluorescent quinoxalines exhibited photophysical properties and solvatochromism in certain rules. Based on control experiments, a plausible reaction mechanism was proposed.

A palladium-catalyzed regiodivergent C₁ insertion multicomponent reaction involving aryne, CO, and 2-iodoaniline is established to construct the scaffolds of phenanthridinone and acridone alkaloids. Regioselective control is achieved under the guidance of selective ligands. The phenanthridinones are solely obtained under ligand-free condition. In comparison, application of the electron-abundant bidentate ligand dppm afforded the acridones with high efficiency. The release rate of the aryne from the precursor assists the regioselectivity of insertion as well, which was revealed through interval NMR tracking. A plausible mechanism was suggested based on the control experiments. Representative natural products and two types of natural product analogues were synthesized divergently through this tunable method.

A palladium-catalyzed regiodivergent C₁ insertion multicomponent reaction involving aryne, CO, and 2-iodoaniline is established to construct the scaffolds of phenanthridinone and acridone alkaloids. Regioselective control is achieved under the guidance of selective ligands. The phenanthridinones are solely obtained under ligand-free condition. In comparison, application of the electron-abundant bidentate ligand dppm afforded the acridones with high efficiency. The release rate of the aryne from the precursor assists the regioselectivity of insertion as well, which was revealed through interval NMR tracking. A plausible mechanism was suggested based on the control experiments. Representative natural products and two types of natural product analogues were synthesized divergently through this tunable method.

This study presents thioether construction involving alkyl/aryl thiosulfates and diazonium salt catalyzed by visible-light-excited [Ru(bpy)₃Cl₂] at room temperature in 44–86 % yield. Electron paramagnetic resonance studies found that thiosulfate radical formation was promoted by K₂CO₃. Conversely, radicals generated from BnSH or BnSSBn (Bn=benzyl) were clearly suppressed, demonstrating the special property of thiosulfate in this system. Transient absorption spectra confirmed the electron-transfer process between [Ru(bpy)₃Cl₂] and 4-MeO-phenyl diazonium salt, which occurred with a rate constant of 1.69×10⁹ M⁻¹ s⁻¹. The corresponding radical trapping product was confirmed by X-ray diffraction. The full reaction mechanism was determined together with emission quenching data. Furthermore, this system efficiently avoided the over-oxidation of sulfide caused by H₂O in the photoexcited system containing Ru²⁺. Both aryl and heteroaryl diazonium salts with various electronic properties were investigated for synthetic compatibility. Both alkyl- and aryl-substituted thiosulfates could be used as substrates. Notably, pharmaceutical derivatives afforded late-stage sulfuration smoothly under mild conditions.

A Pd-catalyzed efficient reductive cross-coupling reaction without metallic reductant to construct a Csp²Csp³ bond has been reported. A Pd^IV complex was proposed to be a key intermediate, which subsequently went through double oxidative addition and double reductive elimination to produce the cross-coupling products by involving Pd^0/II/IV in one transformation. The oxidative addition from Pd^II to Pd^IV was partially demonstrated to be a radical process by self-oxidation of substrate without additional oxidants. Furthermore, the solvent was proved to be the reductant for this transformation through XPS analysis.

This Focus Review presents recent developments in the cleavage of CC bonds in organic molecules. Significant progress in CC activation, including the development of a variety of new synthetic strategies, has contributed to the development of this field over the past few decades. Transition-metal-mediated CC bond cleavage has been shown to be a quite efficient process and several elegant metal-free methods have also recently been developed. Strained rings have been widely used in CC cleavage transformations; however, unstrained CC activation has increasingly caught the attention of organic researchers, which inspired us to clarify the developments in this field.

Trifluoromethylation meets CH activation: after transition metal-catalyzed trifluoromethylation became more and more popular, trifluoromethylation via CH activation is now emerging as the latest attraction. Several pioneering examples and their mechanisms are discussed in this review.

The introduction of sulfur atoms onto target molecules is an important area in organic synthesis, in particular in the synthesis of pharmaceutical compounds, and a wide variety of sulfuration agents have been developed for thionation reactions over the past few decades. In this Focus Review, we collect and summarize the CS bond-formation reactions that have been used to construct CS bonds in natural products and pharmaceutical compounds.

It is well known that Pd⁰ undergoes oxidative addition to organic halides, especially aryl or vinyl halides. In the contrast, the formation of organic halides by reductive elimination of RPd^IIX (X=halogen) has been mostly ignored until very recently. This Focus Review discusses recent developments in palladium-catalyzed carbon–halogen bond formation by the reductive elimination of RPd^IIX. These new developments have enriched the scope of palladium-catalyzed reactions, and provide a new way to construct carbon–halogen bonds.