Preparation and Reactivity of Polystyrene-Supported Iodosylbenzene: Convenient Recyclable Oxidizing Reagent and Catalyst

Abstract

A facile preparation of novel polystyrene-supported iodosylbenzene (PS-ISB, loading of IO up to 1.50 mmol/g) from iodopolystyrene is described. This resin has been successfully used for efficient oxidation of a diverse collection of alcohols to aldehydes and ketones in the presence of BF 3 ·OEt 2 . PS-ISB can also be employed as efficient co-catalyst in combination with RuCl 3 in the catalytic oxidation of alcohols and aromatic hydrocarbons, respectively, to corresponding carboxylic acids and ketones using Oxone as the stoichiometric oxidant.In recent years, hypervalent iodine compounds have been widely used in organic synthesis for various synthetically useful oxidative transformations with many advantages, like mild reaction conditions, simple workup, and the environmentally benign nature of the reagents. 1 Iodosylbenzene, (PhIO) n , is particularly important as an oxygentransfer agent that has found widespread application in catalytic oxygenation reactions after the discovery of its supreme efficacy as a source of oxygen atoms for oxidations catalyzed by cytochrome P-450 and by discrete transition-metal complexes. 2,3 However, stoichiometric amount of iodobenzene as a waste product is produced in these reactions, which leads to low atom economy and complicated isolation and purification of the products. Furthermore, the practical use of iodosylbenzene is hampered by its low stability and potentially explosive properties upon moderate heating and insolubility in most solvents as a result of its polymeric structure, (PhIO) n . 3,4 Polymer-supported hypervalent iodine reagents, however, overcome these drawbacks and have the similar reactivities as their monomeric analogues. 5 Several polystyrenesupported hypervalent reagents previously reported by our group, such as polystyrene-supported (diacetoxyiodo)benzene (PS-DIB), 6a poly{[4-(hydroxy)(tosyloxy)iodo]styrene} (PS-HTIB), 6b polystyrene-supported phenyliodine(III)bis(trifluoroacetate) (PS-PIFA), 6c polystyrene-supported iodosylbenzene sulfate (PS-IBS), 6d are employed as efficient oxidants, polystyrene-supported (dichloroiodo)benzene (PS-DCIB) 6e as chlorination and oxidation reagents, and polystyrene-supported alkenyl(phenyl) iodonium salts 6f as synthons of alkenyl cations. The reduced form of these reagents, iodopolystyrene (PS-IB), can be conveniently recovered from reaction mixtures and reused for the preparation of the reagent.Despite significant interest in polymer-supported hypervalent iodine reagents and the importance of iodosylarenes in organic chemistry, the polystyrene-supported variant of iodosylbenzene (PS-ISB) has not been reported in the literature. Our initial attempts to prepare PS-ISB by a standard approach involving treatment of respective (diacetoxyiodo)arene, PS-DIB, with the aqueous solution of NaOH were unsuccessful. We have found, however, that PS-DIB (1) 6a,7 can be effectively converted into PS-ISB (2) under solvent-free conditions (Scheme 1). 8 A similar solvent-free methodology has previously been used for the preparation of [hydro...

Advances in Synthetic Applications of Hypervalent Iodine Compounds

“…In particular, the practically important reagent, DIB, can be prepared by the direct oxidation of iodobenzene using peracetic acid according to the procedure of Sharefkin and Saltzman . A common procedure for preparing various [bis­(acyloxy)­iodo]­arenes consists of the treatment of substituted iodobenzenes with corresponding peracids; this method is also acceptable for preparing the polymer-supported analogues of DIB from poly­(iodostyrene) or aminomethylated poly­(iodostyrene), ,− and the ion-supported (diacetoxyiodo)­arenes. , Likewise, treatment of various iodoarenes with peroxytrifluoroacetic acid affords the respective [bis­(trifluoroacetoxy)­iodo]­arenes in high yield. − Other oxidants, such as periodates, − chromium­(VI) oxide, sodium percarbonate, m -chloroperoxybenzoic acid ( m CPBA), − potassium peroxodisulfate, , H 2 O 2 –urea, Selectfluor, and sodium perborate, can oxidize iodoarenes in the presence of carboxylic acids to give the corresponding [bis­(acyloxy)­iodo]­arenes. For example, oxidation of aryl iodides using sodium perborate (NaBO 3 ) in acetic acid at 40 °C has been used for preparing numerous (diacetoxyiodo)-substituted arenes and heteroarenes, such as N -tosyl-4-(diacetoxyiodo)­pyrazole, N -trifluoromethanesulfonyl-4-(diacetoxyiodo)­pyrazole, 2-(diacetoxyiodo)­thiophene, and 3-(diacetoxyiodo)­thiophene. − The chiral (diacetoxyiodo)­arene 127 and its derivatives were efficiently prepared by the perborate oxidation of the corresponding aryl iodides (Figure ).…”

“…More recently, several other polymer-supported trivalent iodine reagents have been introduced. Examples of important polymer-bound hypervalent iodine­(III) reagents are illustrated by structures 692 – 697 in Figure . ,,,,,− …”

Hypervalent Iodine‐Catalyzed Oxidative Functionalizations Including Stereoselective Reactions

“…The extension of a similar catalytic approach using RuCl 3 /polystyrene‐supported iodosylbenzene 53 as co‐catalyst in the presence of oxone as oxidant (Scheme ) was also reported 36a. The oxidation products were isolated in moderate to good yields.…”

SiO2-supported RuCl3/3-(dichloroiodo)benzoic acid: green catalytic system for the oxidation of alcohols and sulfides in water

“…However, their low atom economy remains a major drawback, as stoichiometric amounts of aryliodides or similar waste products are produced, which complicates isolation and purification of the products. [29][30] To overcome these disadvantages, recyclable and reusable hypervalent iodine reagents have been developed in recent years, involving both polymeric [31][32][33][34][35][36][37][38][39][40][41][42] and molecular [43][44][45][46][47][48][49][50] species.…”

“…Therefore, as a part of our studies [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] towards the development of practical and environmentally benign oxidation reactions, we herein report the design and synthesis of a recyclable SiO 2 -supported RuCl 3 (SiO 2 -RuCl 3 ) catalyst (Scheme 1) and develop a mild, simple, cost-effective and green procedure for the catalytic oxidation of alcohols and sulfides using the recyclable SiO 2 -RuCl 3 catalyst and 3-(dichloroiodo)benzoic acid as a catalytic oxidative system in water under mild conditions (Scheme 2). 3-(Dichloroiodo)benzoic acid is a readily available and stable hypervalent iodine oxidant that can be easily regenerated and reused.…”