Hypervalent Iodine Reagents in High Valent Transition Metal Chemistry

Abstract

Over the last 20 years, high valent metal complexes have evolved from mere curiosities to being at the forefront of modern catalytic method development. This approach has enabled transformations complimentary to those possible via traditional manifolds, most prominently carbon-heteroatom bond formation. Key to the advancement of this chemistry has been the identification of oxidants that are capable of accessing these high oxidation state complexes. The oxidant has to be both powerful enough to achieve the desired oxidation as well as provide heteroatom ligands for transfer to the metal center; these heteroatoms are often subsequently transferred to the substrate via reductive elimination. Herein we will review the central role that hypervalent iodine reagents have played in this aspect, providing an ideal balance of versatile reactivity, heteroatom ligands, and mild reaction conditions. Furthermore, these reagents are environmentally benign, non-toxic, and relatively inexpensive compared to other inorganic oxidants. We will cover advancements in both catalysis and high valent complex isolation with a key focus on the subtle effects that oxidant choice can have on reaction outcome, as well as limitations of current reagents.

A Continuum from Halogen Bonds to Covalent Bonds: Where Do λ3 Iodanes Fit?

“…Hypervalent iodine compounds (HVI) are important alternatives to transition metal reagents because of their reactivity, synthetic utility, low cost, abundance, and non-toxic nature [1][2][3][4][5][6]. HVIs are involved in a multitude of reactions such as: reductive elimination, ligand exchange, oxidative addition, and ligand coupling [7,8].…”

Hypervalent iodine compounds: reagents of the future

“…68 The development of new synthetic methodologies and the use of hypervalent iodine reagents in specific classes of reactions have attracted significant research activity. Examples of recent reviews dedicated to specific reactions include the following works: applications of hypervalent iodine(III) reagents in direct C-H bond functionalization, 69 iodosobenzene-mediated construction of heterocyclic scaffolds, 70 functionalization of alkenes using hypervalent iodine reagents, 71,72 hypervalent iodine-mediated synthesis of spiroheterocycles, 73 organocatalytic approaches used to promote group transfer from hypervalent iodine species, 74 phenol dearomatization reactions using hypervalent iodine reagents, 75,76 rearrangements induced by hypervalent iodine, 77 applications of hypervalent iodine(III) reagents in organophosphorus chemistry, 78 hypervalent iodine reagents in transition metal chemistry, 79 and many other works. Theoretical studies of the mechanisms of catalytic and stoichiometric iodine-mediated reactions has been discussed in numerous publications.…”

An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode

“…10,11 Hypervalent iodine reagents are commonly used oxidants for oxidative coupling reagents and in group and oxygen transfer reactions. 12,13,14 They can be also applied in benzylic hydroxylations as demonstrated by Groves in his early report as well as in high valent transition metal chemistry 15 and in photoredox catalysis. 16 The use of chiral iodanes or their aryl iodide precursors in catalytic enantioselective benzylic hydroxylations is so far unknown.…”