Arylations Promoted by Hypervalent Iodine Reagents

Abstract

This chapter describes the methodology for metal‐free and metal‐catalyzed arylations with hypervalent iodine reagents. Most commonly, diaryliodonium salts (diaryl‐λ 3 ‐iodanes) are utilized as electrophilic arylating agents, and such arylations are discussed in detail, including chemoselectivity trends with unsymmetric iodonium salts. Arylations with other iodine(III) reagents are also described, and have been successfully utilized especially in metal‐free biaryl synthesis. The field of hypervalent iodine‐mediated arylations is quickly expanding, and the chapter is focused on the recent developments with brief historic backgrounds to each arylation type.

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

“…During the last decade, noteworthy improvement in the synthesis and use of diaryliodonium salts has been reported [9][10][11][12][13][14][15][16][17][18][19][20][21]. Owing to their electron-deficient nature at the iodine center and to the excellent leaving-group ability of the iodoarene, diaryliodonium salts are frequently employed as aromatic electrophiles in aryl transfer processes [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Seminal contributions from the Pike, Olofsson, Kita and Stuart groups highlighted the efficiency and the selectivity of this aforementioned reaction.…”

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

“…Metal-free arylations with diaryliodonium salts generally proceed via ligand exchange to a T-shaped Nu-I intermediate, which undergoes LC to provide Nu-Ar and Ar-I. 11,35 The high reactivity in such transformations is explained by the electrophilicity of the iodine(III) atom and the potent leaving group ability of the hypervalent iodine functionality I + ÀPh. 11,35,48 Direct S N Ar attack on the carbon ipso to the iodine(III) moiety has been investigated as a potential alternative pathway, but DFT calculations only favored such S N Ar under very special circumstances.…”

“…9 The increasing interest for sustainable, transition-metal-free transformations has spurred the development of hypervalent iodine-mediated arylations, primarily using diaryliodonium salts (Ar 2 IX). [10][11][12][13][14] These are easily available, bench-stable, and nonhazardous reagents that have proven to be efficient electrophilic arylation agents with a variety of O-and N-nucleophiles. 11,[15][16][17][18][19][20] Although reactions with…”

“…[10][11][12][13][14] These are easily available, bench-stable, and nonhazardous reagents that have proven to be efficient electrophilic arylation agents with a variety of O-and N-nucleophiles. 11,[15][16][17][18][19][20] Although reactions with…”

“…Hence, we designed a novel diaryliodonium reagent, carrying both a leaving group and a strong EWG, in addition to the highly electron-withdrawing iodonium moiety to evaluate the strategy (Scheme 1C). We speculated that the unusual structure of this reagent might enable an initial S N Ar reaction instead of the usual ligand coupling (LC) pathway 11,35 to deliver a unique iodine(III) intermediate that could undergo a subsequent aryl transfer to yield a diarylated product. Such S N Ar reactivity is unreported and would conceptually expand the chemistry of iodine(III) reagents beyond diarylations.…”