Recent Progress in Synthetic Applications of Cyclic Hypervalent Iodine(III) Reagents

Abstract

Hypervalent iodine compounds have found broad application in modern organic chemistry as reagents and catalysts. Cyclic hypervalent iodine reagents based on the benziodoxole heterocyclic system have higher stability compared to their acyclic analogues, which makes possible the preparation and safe handling of the reagents with special ligands such as azido, cyano, and trifluoromethyl groups. Numerous iodine‐substituted benziodoxole derivatives have been prepared and utilized as reagents for transfer of the substituent on hypervalent iodine to organic substrate. Reactions of these reagents with organic substrates can be performed under metal‐free conditions, in the presence of transition metal catalysts, or using photocatalysts under photoirradiation conditions. In this review, we focus on the most recent synthetic applications of cyclic hypervalent iodine(III) reagents with the following ligands: N3, NHR, CN, CF3, SCF3, OR, OAc, ONO2, and C(=N2)CO2R. The review covers literature published mainly in the last 5 years.magnified image

Hydroxylamine Umpolung in Copper-Catalyzed Cross-Coupling Reactions to Synthesize N-Arylhydroxylamine Derivatives

“…Pittsburgh compound B derivative containing a benzothiazole successfully afforded N-arylhydroxylamine 26. The reaction conditions were also compatible with many N-heterocycles and the corresponding N-arylhydroxylamine was produced in good yields from quinoline (27), pyridine (28), azaindole (29), indole (30), pyrazole (31), pyrimidine (32), thiophene (33), furan (34), and pyrrole (35) containing boronic acids. In some cases, the protodeboration byproduct was observed.…”

“…Over the past years, hypervalent iodine­(III) (HVI) has emerged as a versatile and environmentally friendly reagent for the transfer of various nitrogen derivatives. , Several nitrogen-containing HVIs (azide, amide, and saccharin) bearing a reactive N–I bond − have been developed to undergo transition metal-catalyzed reactions, namely, the C–H insertion amination via the formation of nitrogen radicals . The electrophilic copper-catalyzed cross-coupling reaction with the diarylmethyleneamino-HVI reagent has also been reported to form a C­(sp 2 )–imine bond, via an aminyl radical in the absence of an external oxidant (Figure C) .…”

Amino‐λ3‐iodane‐Enabled Electrophilic Amination of Arylboronic Acid Derivatives

“…We initially investigated the synthesis of an NH 2 ‐substituted hypervalent iodine reagent, which is a promising reagent for the direct synthesis of primary amines but has never been synthesized. An iodine reagent having a benziodoxolone skeleton was selected in consideration of the stability of the target compound [18b,20] . A ligand exchange of the acetoxy group of 1‐acetoxy‐1,2‐benzodioxol‐3‐(1 H )‐one ( 2 ) with commercially available hexamethyldisilazane (R=H, 3 a ) as an ammonia surrogate was then examined, which resulted in a low yield of 1 a with the formation of unidentified inseparable byproducts.…”

Organohypervalent heterocycles

“…Cyclic hypervalent iodine compounds are particularly vital reagents because of their higher thermal stability and modified reactivity compared to that of their acyclic analogues. 344,350–352 The higher thermal stability associated with cyclic iodanes can be attributed to the link between apical and equatorial ligands present at the iodine centre, causing pseudorotation and reductive elimination, which makes thermal decomposition quite difficult. 24–27 The synthetically significant classes of cyclic iodanes are shown in Fig.…”