Metal‐Free Arylation of Oxygen Nucleophiles with Diaryliodonium Salts

Abstract

Phenols and carboxylic acids are efficiently arylated with diaryliodonium salts. The reaction conditions are mild, metal free, and avoid the use of halogenated solvents, additives, and excess reagents. The products are obtained in good-to-excellent yields after short reaction times. Steric hindrance is very well tolerated, both in the nucleophile and diaryliodonium salt. The scope includes ortho- and halo-substituted products, which are difficult to obtain by metal-catalyzed protocols. Many functional groups are tolerated, including carbonyl groups, heteroatoms, and alkenes. Unsymmetric salts can be chemoselectively utilized to obtain products with hitherto unreported levels of steric congestion. The arylation has been extended to sulfonic acids, which can be converted to sulfonate esters by two different approaches. With recent advances in efficient synthetic procedures for diaryliodonium salts the reagents are now inexpensive and readily available. The iodoarene byproduct formed from the iodonium reagent can be recovered quantitatively and used to regenerate the diaryliodonium salt, which improves the atom economy.

Arylation with Unsymmetrical Diaryliodonium Salts: A Chemoselectivity Study

“…Phenols and carboxylic acids are arylated with good chemoselectivity, which is either controlled by electronic factors or ortho substituents 13a. The observed chemoselectivity with a certain salt can otherwise vary greatly with the type of nucleophile,2a, 8d, 14ab as demonstrated in the arylation of aniline and fluoride with three different unsymmetrical salts 15…”

Metal-free formal synthesis of phenoxazine

“…The O -arylation of 2-iodophenol ( 4 ) with salt 5a was investigated using our previously reported methodology [24–25]. As expected, the reaction proceeded well, both in THF and toluene, of which the latter was most appealing as it might allow a tandem arylation and cyclization to reach N -acetylphenoxazine ( 2 ) in one pot.…”

Diaryliodonium Salts in Organic Syntheses: A Useful Compound Class for Novel Arylation Strategies

“…The extended substrate scope of this transformation and the arylation of sulfonic acids were also demonstrated one year later. 15 …”

“…With the utilization of diaryliodonium salts sterically crowded aryl esters (16) can be synthesized from carboxylic acids (15). 22 The transformation was suitable for both aromatic and aliphatic substrates and the transformation provided the desired esters in good yield in short reaction times (Scheme 8).…”

“…Sulfonic acids were also suitable starting materials for the appropriate sulfonester synthesis. 15 In the presence of a bulky base, sulfonic acids (17) could be transformed to the corresponding sulfonates (18) in a short reaction time in refluxing toluene (Scheme 9).…”