Study and Applications of Tetrasubstituted Hypervalent Selenium–Halogen Species in Catalytic Electrophilic Halogenations

Abstract

Electrophilic halogenation reactions are highly useful in various areas. N-Haloamides are commonly used as halogen sources because of high stability and commercial availability. In order to activate N-haloamides, Lewis basic chalcogens are commonly used as catalysts to site-isolate the strongly coordinating amide moieties. However, the corresponding trisubstituted chalcogenonium–halogen cationic intermediate is sensitive to moisture and nucleophiles, leading to poor compatibility in some reactions. Herein, we report an efficient catalytic halogenation protocol using phenyl selenium with ortho-substituted carboxylic acid as the catalyst. Mechanistic study suggests that a tetrasubstituted neutral hypervalent Se–halogen species is responsible for the high reactivity. This active intermediate was found to be moisture-stable, and the catalytic system is applicable to a wide range of electrophilic functionalization reactions including haloamidation, intermolecular haloesterification, halocycloetherification, halolactonization, aromatic halogenation, halopolyene cyclization, and selenylation reactions.

Telluronium‐Catalyzed Halogenation Reactions: Chalcogen‐Bond Activation of N‐Halosuccinimides and Catalysis

“…They nevertheless required longer reaction time. [31] It is worth also mentioning that in the reactions detailed above, no degradation of the catalyst was observed, as checked by 19 F NMR spectroscopy on the crudes after reaction.…”

“…The authors have cited additional references within the Supporting Information. [34][35][36][37][38][39][40][41][42][43][44][45][46][47]…”

Chalcogen Bond Catalysis with Telluronium Cations for Bromination Reaction: Importance of Electrostatic and Polarization Effects

“…[14] Recently, Yeung et al reported an efficient catalytic bromination of anisole using phenyl selenium with ortho-substituted carboxylic acid as the catalyst. [15] They found that the ChB catalysts could significantly increase the rate and yield of the reaction. Moreover, Mamane's group reported impressive ChBs with telluronium cations in the bromination of anisole, which demonstrated that NBS significantly activated by the telluronium cations catalysts.…”

“…Recently, Yeung et al . reported an efficient catalytic bromination of anisole using phenyl selenium with ortho‐substituted carboxylic acid as the catalyst [15] . They found that the ChB catalysts could significantly increase the rate and yield of the reaction.…”

Directing Group Strategy for the Isolation of Organoselenium(VI) Benzoselenonates: Metal-Free Catalysts for Hydrogen Evolution Reaction

“…Mainly the low-valent organoselenium compounds with oxidation states of Se 0 , Se II , and Se IV , have been explored in synthetic chemistry, , materials, and in biology . The isolation of selenium in its highest oxidation state is difficult owing to inherent thermodynamic instability attributed to scandide contraction , in which period 4 elements (Ga, Ge, As, Se, Br, Kr) tend to be smaller in size and possess higher ionization energies .…”