Synthesis, Characterization, and Reaction of Crown Ether Complexes of Aqua(hydroxy)(aryl)iodonium Ions

Abstract

The Koser reagent, [hydroxy(tosyloxy)iodo]benzene (1; Ts = p-toluenesulfonyl), is a useful oxidizing agent for a range of organic substrates.[1] It has been reported that upon dissolution in water the l 3 -iodane undergoes complete ionization to give the hydroxy(phenyl)iodonium cation (PhI + OH).[2] The hydroxy(phenyl)iodonium ion does not form an ion pair with a tosylate ion and is presumed to be ligated with at least one water molecule at an apical site of the iodine(iii) center. This aqua(hydroxy)(phenyl)iodonium ion 2 (L = H 2 O) is highly soluble in water with a pK a value of 4.30 at 20 8C.Iodosylbenzene is a polymer bridged by secondary I···O hypervalent interactions, [3] and hence is essentially insoluble in both nonreactive organic solvents and water at near neutral pH conditions; [4] however, at pH < 2.3 iodosylbenzene is highly soluble in water, in which 2 (L = H 2 O) was also assumed to be a primary monomeric species. [2] Aqua complexes of l 3 -iodanes with a water molecule coordinated to an iodine(iii) center are unique, and there are no well-established precedents. Therefore, direct evidence supporting the proposed structure of 2 (L = H 2 O) is highly desirable. Recently, Wirth and co-workers synthesized an interesting chiral hydroxyiodonium ion 3, in which the oxygen atom of the ortho methoxymethyl group replaces the tosylate ligand of the Koser reagent with a near-linear O À I···O triad. [5] We have reported the isolation and characterization of the crown ether complex 2·BF 4 À (L = [18]crown-6) of hydroxy-(phenyl)iodonium ion. In this complex, an oxygen atom of the crown ether is tightly bound to the iodine(iii) center at the apical site and forms a T-shaped structure with linear OÀI···O hypervalent bonding.[6] Herein, we report the first synthesis

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 ).…”

Ventricular septal rupture masquerading as coronary perforation during intervention for acute myocardial infarction

“…We reported that the reaction of (diacetoxyiodo)benzene with trimethylsilyl trifluoromethanesulfonate (TMSOTf) in the presence of 18C6 in dichloromethane affords the aqua crown ether complex 6a in high yield (Scheme ) 18. The aqua complex 6a is soluble in dichloromethane, MeCN, and MeOH, but not in less polar diethyl ether and hexane.…”

Synthesis of secondary and tertiary amides without coupling agents from amines and potassium acyltrifluoroborates (KATs)

“…Hu reported a copper-catalyzed oxidation of phenyl-triuoroborate, 20 Fensterbank a TEMPO-promoted procedure, 21 and Ochiai employed a hypervalent iodonium complex. 22 Of greatest relevance are Molander's oxidation conditions using Oxone 23 and Kandasamy's report using hydrogen peroxide in lactic acid for the oxidation of phenyl-triuoroborate. 24 These conditions, however, are relatively harsh and not consistent with the rapid, clean oxidations we observed.…”