The Role of Iodanyl Radicals as Critical Chain Carriers in Aerobic Hypervalent Iodine Chemistry

Abstract

Aerobic hypervalent iodine chemistry provides a strategy for coupling the oneelectron chemistry of O 2 with two-electron processes typical of organic synthesis. We show that in contrast to the canonical two-electron oxidation of aryl iodides, aerobic synthesis proceeds by a radical chain process initiated by the addition of aerobically generated acetoxy radicals to aryliodides to generate iodanyl radicals. Robustness analysis reveals that the developed aerobic oxidation chemistry displays substrate tolerance similar to that observed in peracid-based methods and thus holds promise as a sustainable synthetic method.

Electrocatalytic C–N Coupling via Anodically Generated Hypervalent Iodine Intermediates

“…I(II) species; Figure 1). 15 We speculated that electrolysis of aryl iodides in the presence of acetate sources may provide access to the same iodanyl radicals and thus enable hypervalent iodine electrocatalysis. Here, we report that facile acetate-dependent anodic oxidation of aryl iodides enables hypervalent iodine electrocatalysis of both intra-and intermolecular C-H / N-H coupling reactions.…”

“…For this reason, the developed aerobic oxidation conditions display substrate scope limitations similar to those displayed by peracid conditions when assayed by robustness analysis. 15,24 We were interested in evaluating the robustness of the developed hypervalent iodine electrocatalysis to evaluate if a broader functional group tolerance may be achieved by avoiding the use or evolution of peracids. Figure 4 displays both the impact of a variety of small-molecule additives on the yield of intramolecular C-H/N-H coupling as well as the amount of recovered additive following the electrochemical reaction (see also Figure S5).…”

Photoinduced Aerobic Iodoarene‐Catalyzed Spirocyclization of N‐Oxy‐amides to N‐Fused Spirolactams**

“…This strategy was eventually implemented in 2017 by Miyamoto & Uchiyama [23] and Powers [24] who independently reported the first examples of aerobic oxidation of iodoarenes. Both approaches are based on the formation of a suitable oxidant during the O 2 ‐mediated autoxidation of aldehydes, [25–27] although the protocols slightly differ. The Miyamoto‐Uchiyama protocol requires a sterically hindered aldehyde and was applied to the glycol scission of 1,2‐diols and the Hofmann rearrangement of primary amides with only 3 to 5 equivalents of iso ‐butyraldehyde and 5 to 20 mol % of pentamethyliodobenzene [23] .…”

“…Oxidation of the latter into Pyry + by the dioxygen would close the photoredox catalytic cycle and generate the superoxide ion [50] . Iodoaryl radical cation B has been proposed as an intermediate in the anodic generation of iodine(III) reagents [19] and could serve as a precursor to iodanyl radical C , [27] upon reaction with the solvent. After combination with the superoxide and protonation peroxy‐iodinane D could be formed.…”

Electrocatalytic C–N Coupling via Anodically Generated Hypervalent Iodine Intermediates

“…For this reason, the developed aerobic oxidation conditions display substrate scope limitations similar to those displayed by peracid conditions when assayed by robustness analysis. 15,24 We were interested in evaluating the robustness of the developed hypervalent iodine electrocatalysis to evaluate if a broader functional group tolerance may be achieved by avoiding the use or evolution of peracids. Figure S5).…”