Bidentate Nitrogen-Ligated I(V) Reagents, Bi(N)-HVIs: Preparation, Stability, Structure, and Reactivity

Abstract

Hypervalent iodine­(V) reagents are a powerful class of organic oxidants. While the use of I­(V) compounds Dess–Martin periodinane and IBX is widespread, this reagent class has long been plagued by issues of solubility and stability. Extensive effort has been made for derivatizing these scaffolds to modulate reactivity and physical properties but considerable room for innovation still exists. Herein, we describe the preparation, thermal stability, optimized geometries, and synthetic utility of an emerging class of I­(V) reagents, Bi­(N)-HVIs, possessing datively bound bidentate nitrogen ligands on the iodine center. Bi­(N)-HVIs display favorable safety profiles, improved solubility, and comparable to superior oxidative reactivity relative to common I­(V) reagents. The highly modular synthesis and in situ generation of Bi­(N)-HVIs provides a novel and convenient screening platform for I­(V) reagent and reaction development.

Oxidation of Electron-Deficient Phenols Mediated by Hypervalent Iodine(V) Reagents: Fundamental Mechanistic Features Revealed by a Density Functional Theory-Based Investigation

“…A recent study investigating the stability of isomers of a related Bi(bipy)-HVI species also found that an isomer structure analogous to structure 1 is the most stable. 6 This consistency suggests that regardless of the electronic nature of the bidentate nitrogen ligand, isomer 1 is likely to be lower in energy than the other possible systems.…”

Polyhalogenation-Facilitated Spirolactonization at the meta-Position of Phenols

“…The reaction did not deliver any product without a base (Table , entry 1). Different bases containing nitrogen were tested, and as a result, pyridine showed great performance (entries 2–10), affording the corresponding product 2a in 21% yield. The structure of 2a was confirmed through single-crystal X-ray diffraction analysis.…”

λ3‐ and λ5‐Iodanes: Substituent Effects and Pseudorotation/Hypervalent Twisting

“…In 2019, Wengryniuk et al. successfully performed dearomatization of electron‐deficient phenols 62 by reacting with in situ‐generated λ 5 ‐iodane ( 63 – 65 ), Scheme 14 [90–92] …”

“…The modified iodanes possess weak bidentate linkers, i.e., bipyridines, which were found to facilitate the crucial steps for oxidation, i.e., ligand exchange, hypervalent twist, and elimination [70,78,91] . For example, iodane 64 with electron‐deficient bipyridine showed better reactivity than 63 .…”

“…[89] In 2019, Wengryniuk et al successfully performed dearomatization of electron-deficient phenols 62 by reacting with in situ-generated λ 5 -iodane (63-65), Scheme 14. [90][91][92] The modified iodanes possess weak bidentate linkers, i.e., bipyridines, which were found to facilitate the crucial steps for oxidation, i.e., ligand exchange, hypervalent twist, and elimination. [70,78,91] For example, iodane 64 with electrondeficient bipyridine showed better reactivity than 63.…”