Copper-Catalyzed Indole-Selective C-N Coupling Reaction of Indolyl(2-alkoxy-phenyl)iodonium Imides: Effect of Substituent on Iodoarene as Dummy Ligand

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.

(Indol-3-yl)(DMIX)Iodonium Salts: Novel Electrophilic Indole Reagents

A new umpolung approach to the C3-H functionalization of indoles with diverse nucleophiles based on the intermediate formation of I(III) reagents is described. The 3,5-dimethylisoxazol-4-yl auxiliary allows for selective indole transfer under catalyst-free conditions, which was impossible using previously reported reagents. Combining the mildness of transition-metal-free conditions and the high reactivity of hypervalent iodine reagents, this protocol tolerates various functional groups and provides access to indoles that are difficult to prepare conventionally.

Mechanistic duality of indolyl 1,3-heteroatom transposition

A novel mechanistic duality has been revealed from the indolyl 1,3-heteroatom transposition (IHT) of N-hydroxyindole derivatives. A series of in-depth mechanistic investigations suggests that two separate mechanisms are operating simultaneously. Moreover, the relative contribution of each mechanistic pathway, the energy barrier for each pathway, and the identity of the primary pathway were shown to be the functions of the electronic properties of the substrate system. Based on the mechanistic understanding obtained, a mechanism-driven strategy for the general and efficient introduction of a heteroatom at the 3-position of indole has been developed. The reaction developed exhibits a broad substrate scope to provide the products in various forms of the functionalised indole. Moreover, the method is applicable to the introduction of both oxygen- and nitrogen-based functional groups.

N-Acylimino-λ3-iodanes from the Metathesis of Iodosoarenes and Nitriles for the Photoinduced C-H Perfluoroacylamination of (Hetero)Arenes

An efficient and scalable synthesis of N-perfluoroacylimino-λ³-iodanes was achieved via an unprecedented metathesis between iodosoarenes and perfluoroalkanenitriles. The perfluoroacylamino groups of the iodanes could be introduced to aromatic and heteroaromatic rings using photoirradiation.

A bench-stable N-trifluoroacetyl nitrene equivalent for a simple synthesis of 2-trifluoromethyl oxazoles

ortho-Nitro-substituted N-trifluoroacetyl imino-λ³-iodane is a bench-stable trifluoroacetyl nitrene precursor, in which intra- and intermolecular halogen bonding (XB) plays an important role. Potential synthetic applications of this novel precursor were explored.

C-H Sulfonylation via 1,3-Rearrangement of Sulfonyl Group in N-Protected 3-Bis-sulfonimidoindole Derivatives Using Fluorine Reagent

A C-H sulfonylation of N-protected 3-bis-sulfonimidoindole derivatives via a 1,3-rearrangement of a sulfonyl group on a bis-sulfonimide moiety using tetra-n-butylammonium fluoride (TBAF) was developed to provide 2-sulfonyl-3-sulfonamidoindole derivatives in high yields as a novel C_sp2-H functionalization of heterocycles. The rearrangement of the sulfonyl group proceeded through an intermolecular addition of the desorbed sulfinyl ion from the bis-sulfonimide moiety in the substrate.

Cu-Catalyzed Oxidative 3-Amination of Indoles via Formation of Indolyl(aryl)iodonium Imides Using o-Substituted (Diacetoxyiodo)arene as a High-Performance Hypervalent Iodine Compound

An oxidative 3-amination of indole derivatives using hypervalent iodine(III) and bissulfonimides, which proceeds via the formation of indolyl(aryl)iodonium imides, was developed. This reaction was followed by an indole-selective copper-catalyzed oxidative C–N coupling reaction to obtain 3-amino indole derivatives as single regioisomers. o-Alkoxy(diacetoxyiodo)arenes showed higher reactivity in the reaction than o-alkyl(diacetoxyiodo)arenes, efficiently promoting the formation of indolyl(aryl)iodonium imides in the first step.