Transition Metal‐FreeO‐Arylation ofN‐Alkoxybenzamides Enabled by Aryl(trimethoxyphenyl)iodonium Salts

Abstract

Herein, we develop a metal catalyst‐free protocol for O‐arylation of benzamide hydroxamate esters. The chemoselective O‐ versus N‐arylation of the amides was tuned by varying the electronic and/or steric properties of the diaryliodonium salt and/or the substrate. The O‐arylation reaction would preferentially occur for sterically and electronically diverse substrates. This study, which reveals the possibility of substituent‐ and reagent‐controlled chemoselectivity, with diaryliodonium salts might attract interest in the area of hypervalent iodine chemistry.magnified image

Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions

“…Furthermore, phenyliodine(III) bis(trifluoroacetate) was used as a starting material under the optimized reaction conditions and the corresponding phenyl(TMP)iodonium(III) trifluoroacetate ( 4m ) was obtained in 91% yield. These aryl(TMP)iodonium(III) acetates were recently utilized by our group for the arylation of phenols [ 13 ] and N -alkoxyamides [ 26 , 29 ], exhibiting excellent reactivity and aryl group selectivity.…”

“…Electron-rich aryl ligands derived from anisole, mesitylene, and particularly 1,3,5trimethoxybenzene are highly recommended for chemoselective arylation processes. Aryl(TMP)iodonium(III) salts have been successfully used as transition metal-free arylating reagents for various nucleophiles such as nitrogen- [23][24][25][26], oxygen- [13,[27][28][29], sulfur- [30], and carbon- [31] nucleophiles due to their excellent reactivity and aryl group selectivity over aryl(anisyl)iodonium(III) salts [32] and aryl(mesityl)iodonium(III) salts [33].…”

Copper-Catalyzed Chemoselective O-Arylation of Oxindoles: Access to Cyclic Aryl Carboxyimidates

“…15 Recently, Dohi et al demonstrated a basemediated O-arylation of benzamide hydroxamate esters using unsymmetrical diaryl iodonium salts (Scheme 1a). 16 Chen and their co-workers also reported iodonium salt-assisted Oarylation of pyridyl amidates with Cu(OTf) 2 as a catalyst (Scheme 1b). 17 In this context, 2-aryloxy pyridine derivatives were also synthesized with iodonium salts, but the substrate selection was limited to C-6 substitution.…”

“…For example, Wen and their team developed a method using Ni­(OTf) 2 catalyst to derive benzoxazole derivatives intramolecularly . Recently, Dohi et al demonstrated a base-mediated O-arylation of benzamide hydroxamate esters using unsymmetrical diaryl iodonium salts (Scheme a) . Chen and their co-workers also reported iodonium salt-assisted O-arylation of pyridyl amidates with Cu­(OTf) 2 as a catalyst (Scheme b) .…”

Silver-Catalyzed Coupling of Unreactive Carboxylates: Synthesis of α-Fluorinated O-Aryl Esters

“…Among the various combinations of aryl ligands, TMP-iodonium salts (Ar­(TMP)­I + X – ) , and Mes-iodonium salts (Ar­(Mes)­I + X – ) have been employed for the unified chemoselective aryl transfer. Our group has developed efficient transition-metal-free arylations of various nucleophiles utilizing easily accessible TMP-iodonium salts to synthesize various aryl derivatives. , By contrast, the reaction of α,α-difluoro-β-keto acid sodium salt underwent decarboxylative ligand coupling to afford α-aryl-α,α-difluoromethyl aryl ketones . Here, we describe the unprecedented O -arylation of α-fluorinated carboxylic acid salts with TMP-iodonium salts, affording various fluorine-containing O -aryl esters.…”