Redetermination of the Structure of a Water-Soluble Hypervalent Iodine(V) Reagent AIBX and Its Synthetic Utility in the Oxidation of Alcohols and Synthesis of Isoxazoline N-Oxides

Abstract

The structure of a water-soluble hypervalent iodine(V) reagent AIBX is re-examined through its singlecrystal X-ray analysis and theoretical calculations including Mayer bond order and localized orbital locator (LOL) and AIBX is believed to be a pseudocyclic iodylarene because of the strong electron-withdrawing nature of the trimethylammonium cation on its phenyl ring, which would decrease the electron density of carboxylic anion and make the orthocarboxyl oxygen anion incapable to form hypervalent bond with iodine atom. However, the cyclic benziodoxole structure of AIBX could be obtained by adding a Brønsted acid, which was supported by the calculation result including the increase of Mayer bond order and the shortening of the I−O bond length. Moreover, the fact that the system of AIBX and TFA could oxidize various alcohols to their corresponding carbonyl compounds would indicate that AIBX constitutes a cyclic benziodoxole structure under acidic conditions. In addition, an efficient method has been developed for the synthesis of isoxazoline N-oxides via AIBX-induced dehydrogenative cyclization using β-keto esters as substrates and methyl nitroacetate as a nucleophile.

Selectivity of Oxidizing Agents toward Axial and Equatorial Hydroxyl Groups

“…13 C­{ 1 H} NMR (101 MHz, CDCl 3 ) δ 212.8 (C-1), 46.8 (C-4), 41.5 (C-2), 32.6 (C-5), 27.7 (C-6), 27.7 (C-3). The NMR analysis is consistent with previously reported results . Anal.…”

Five-Membered Hetarene N-Oxides: Recent Advances in Synthesis and Reactivity

“…The generated intermediates 18 undergo subsequent cyclization to afford the target heterocycles 15 (Scheme 6). 18…”

Singlet Oxygen Generation from a Water-Soluble Hypervalent Iodine(V) Reagent AIBX and H2O2: An Access to Artemisinin

“…However, the yields of 1 O 2 (46% and 55%, respectively) are only moderate, which limits the synthetic utility of these combinations. Because the moderate yield of 1 O 2 obtained from H 2 O 2 /PhIO 2 might be due to the poor water solubility of PhIO 2 in aqueous H 2 O 2 , we speculated that the yield could be improved by using a more water-soluble hypervalent iodine reagent, such as AIBX (Figure ), a bench-stable, recyclable zwitterionic pseudocyclic iodylarene that we reported in 2011 . AIBX, which is air- and moisture-stable and can be stored at ambient temperature for at least 3 months without decomposition, bears a carboxylate anion and a trimethylammonium cation at the ortho and para positions of the phenyl ring, respectively, which make this compound highly water-soluble (up to 0.38 M at room temperature).…”