Reactivity of Hydroxy‐ and Aquo(hydroxy)‐λ³‐iodane–Crown Ether Complexes

Abstract

We have designed a series of hydroxy(aryl)-λ(3)-iodane-[18]crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ(3)-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ(3)-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

“…This secondary intermolecular interaction is responsible for increasing the stability of this complex. The same group reported the aqua complexes of iodosylarenes 17 – 19 with one molecule of water coordinated to the hypervalent iodine, which were prepared by treatment of (diacetoxyiodo)­arenes with trimethylsilyl triflate or bis­(trifluoromethylsulfonyl)­imide in the presence of 18-crown-6 ether in dichloromethane. , Single-crystal X-ray study revealed that these aqua complexes also have the T-shaped structure with two apical positions of the iodine­(III) atom occupied by OH and one molecule of water. The presence of 18-crown-6 ether also has a stabilizing effect on iodine complexes (Figure ).…”

“…Activated iodosylbenzenes 16 and 17 are useful oxidants for oxidation of phenols, sulfides, styrene, and silyl enol ethers in water to afford the corresponding oxidation products (Scheme ). ,− The activated iodosylbenzene 16 reacts with alkene 52 in water to give the product of double bond cleavage 53 in good yield (Scheme ). , This is a convenient procedure that can serve as a safe alternative to the ozonolysis reaction.…”

Role of Lewis‐Base‐Coordinated Halogen(I) Intermediates in Organic Synthesis: The Journey from Unstable Intermediates to Versatile Reagents

“…So far, numerous applications of hypervalent halogens, mostly hypervalent iodine, have been explored. Whereas iodine(III) and iodine(V) have been extensively studied, little is known about halogen(I) intermediates owing to their unstable nature. Moreover, systematic accounts focusing on their reactivity upon interaction with Lewis bases are rare.…”

Acid Activation in Phenyliodine Dicarboxylates: Direct Observation, Structures, and Implications

“…The reaction afforded PhI­(OAc)­(OTf) (76% yield), a species previously obtained by Stang and co-workers from PhIO and recently observed (MS, 1 H NMR) by the groups of Gade and Dutton (Scheme ). While the compound is highly unstable, Ochiai, Miyamoto and co-workers did characterize its hydrolysis (aqua) product in the presence of [18]­crown-6 . Now, X-ray quality crystals of this reagent were obtained by storing a CH 2 Cl 2 solution at −25 °C under argon.…”