Diverse reactivity of the gem-difluorovinyl iodonium salt for direct incorporation of the difluoroethylene group into N- and O-nucleophiles

Regioselective Nickel-Catalyzed Hydroarylation of gem-Difluoroalkenes for the Synthesis of the ArCF 2 - ${\rm{ArCF}}_{{2}^{-}}$ Moiety

The incorporation of fluorine and fluorinated functional groups into organic molecules alters their physicochemical properties, thereby facilitating the advancement of novel therapeutics, agricultural chemicals, biological probes, and materials. Nevertheless, there remains a deficiency of methodologies for the catalytic synthesis of certain significant fluorine-containing groups, such asArCF 2 - ${\rm{ArCF}}_{{2}^{-}}$ , under mild conditions utilizing earth-abundant metals. Herein, we report a method for the regioselective hydroarylation of gem-difluoroalkenes under mild conditions with the aid of Ni─H intermediate catalysis, which is capable of efficiently synthesizing compounds containing theArCF 2 - ${\rm{ArCF}}_{{2}^{-}}$ structural motifs and possesses good functional group tolerance.

Arrangement of σ-holes at the halogen atom in halonium cations

Halonium cations are key entities that can stabilize transition states in organocatalysis. The distribution of the electrostatic potential on the crystal structures and theoretical models was investigated in the current study. The Cambridge Structural Database (CSD) survey revealed 478 structures of the [L⋯X⋯L]+ (X - halogen atom, L - ligands attached to the halogen) structural motif, which were divided by the values of the L⋯X⋯L angles. The value of this angle determined the number of σ-holes at the halonium cation and hence its ability to accommodate nucleophilic attack. Complexation with HCN as a Lewis base showed that one or two such ligands can be attracted depending on the number of σ-holes. Further investigation into the electrostatic potential distribution on the surface of the model halonium [HF2C2-X-C2F2H]+ cations revealed that altering the values of the C⋯X⋯C angles leads to the following consequences: two σ-holes can merge into a single belt-like region, or they may both disappear entirely. The unusual fluctuations in the distribution of σ-holes caused by such geometry maneuvering were observed.

Selective radical-type perfluoro-tert-butylation of unsaturated compounds with a stable and scalable reagent

Despite the promising potential of the perfluoro-tert-butyl group in diverse fields such as magnetic resonance imaging, material science and drug design, incorporating this group into organic molecules is still a formidable task, primarily due to its bulky structure and unique fluorine effect. Herein, we describe a stable and scalable reagent for radical-type perfluoro-tert-butylation, which is synthesized in large scale from commercial perfluoro-tert-butanol and a designed benzothiazole hypervalent iodonium salt. Highly E-selective photo-driven C(sp2)-H functionalization of styrene derivatives is achieved in a triplet-triplet energy transfer halted manner, while thermally disfavored Z-products are also accessible by removing the energy antagonist. The application of this method is further demonstrated by late-stage functionalization and divergent synthesis of perfluoro-tert-butylated compounds.

Recent Progress in Synthetic Applications of Hypervalent Iodine(III) Reagents

Hypervalent iodine(III) compounds have found wide application in modern organic chemistry as environmentally friendly reagents and catalysts. Hypervalent iodine reagents are commonly used in synthetically important halogenations, oxidations, aminations, heterocyclizations, and various oxidative functionalizations of organic substrates. Iodonium salts are important arylating reagents, while iodonium ylides and imides are excellent carbene and nitrene precursors. Various derivatives of benziodoxoles, such as azidobenziodoxoles, trifluoromethylbenziodoxoles, alkynylbenziodoxoles, and alkenylbenziodoxoles have found wide application as group transfer reagents in the presence of transition metal catalysts, under metal-free conditions, or using photocatalysts under photoirradiation conditions. Development of hypervalent iodine catalytic systems and discovery of highly enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important recent achievement in the field of hypervalent iodine chemistry. Chemical transformations promoted by hypervalent iodine in many cases are unique and cannot be performed by using any other common, non-iodine-based reagent. This review covers literature published mainly in the last 7-8 years, between 2016 and 2024.

Direct electrophilic and radical isoperfluoropropylation with i-C3F7-Iodine(III) reagent (PFPI reagent)

The isoperfluoropropyl group (i-C3F7) is an emerging motif in pharmaceuticals, agrichemicals and functional materials. However, isoperfluoropropylated compounds remain largely underexplored, presumably due to the lack of efficient access to these compounds. Herein, we disclose the practical and efficient isoperfluoropropylation of aromatic C-H bonds through the invention of a hypervalent-iodine-based reagent-PFPI reagent, that proceeds via a Ag-X coupling process. The activation of the PFPI reagent without any catalysts or additives was demonstrated in the synthesis of isoperfluoropropylated electron-rich heterocycles, while its activity under photoredox catalysis was shown in the synthesis of isoperfluoropropylated non-activated arenes. Detailed mechanistic experiments and DFT calculations revealed a SET-induced concerted mechanistic pathway in the photoredox reactions. In addition, the unique conformation of i-C3F7 in products, that involved intramolecular hydrogen bond was investigated by X-ray single-crystal diffraction and variable-temperature NMR experiments.