Iodobenzene/Oxone

Types of reaction C-O and C-S bond formation Reaction conditions Methanol, room temperature Synthetic strategy Oxidative desulfurization Catalyst Iodobenzene/Oxone /Et3N... 

Keywords Thiosemicarbazides, iodobenzene, Oxone , triethylamine, hypervalent iodine, methanol, room temperature, oxidative sulfurization, oxadiazoles, bisdiaiylthiourea, thia-diazoles, azole derivatives... 

Kennedy and Stock reported the first use of Oxone for many common oxidation reactions such as formation of benzoic acid from toluene and of benzaldehyde, of ben-zophenone from diphenyhnethane, of frawi-cyclohexanediol Ifom cyclohexene, of acetone from 2-propanol, of hydroquinone from phenol, of e-caprolactone from cyclohexanone, of pyrocatechol from salicylaldehyde, of p-dinitrosobenzene from p-phenylenediamine, of phenylacetic acid from 2-phenethylamine, of dodecylsulfonic acid from dodecyl mercaptan, of diphenyl sulfone from diphenyl sulfide, of triphenylphosphine oxide from triphenylphosphine, of iodoxy benzene from iodobenzene, of benzyl chloride from toluene using NaCl and Oxone and bromination of 2-octene using KBr and Oxone . Thus, they... 

Protonated iodosylbenzene species can be generated in solution by the oxidation of iodobenzene with Oxone (2KHS05-KHS04-K2S04) in aqueous acetonitrile. The presence of protonated iodosylbenzene [PhIOH]+ in such solutions has been supported by ESI mass spectrometry [108]. This procedure has been utilized in catalytic oxidations using iodobenzene as the pre-catalyst and Oxone as the stoichiometric oxidant (Section 4.1) [109]. 

Alkylcarboxamides can be converted into the respective amines by Hofinann rearrangement using hypervalent iodine species generated in situ from iodobenzene and a terminal oxidant, such as Oxone (2KHSO5 KHSO4 K2SO4) or m-chloroperoxybenzoic acid (mCPBA). In particular, a convenient experimental procedure for the preparation of alkylcarbamates using Oxone as the oxidant in the presence of iodobenzene in methanol (Scheme 3.166) has been developed [359]. 

Hypervalent iodine species were demonstrated to have a pronounced catalytic effect on the metalloporphyrin-mediated oxygenations of aromatic hydrocarbons [93]. In particular, the oxidation of anthracene (114) to anthraquinone (115) with Oxone readily occurs at room temperature in aqueous acetonitrile in the presence of 5-20 mol% of iodobenzene and 5 mol% of a water-soluble iron(llI)-porphyrin complex (116) (Scheme 4.57) [93]. 2-ferf-Butylanthracene and phenanthrene also can be oxygenated under similar conditions in the presence of 50 mol% of iodobenzene. The oxidation of styrene in the presence of 20 mol% of iodobenzene leads to a mixture of products of epoxidation and cleavage of the double bond. Partially hydrogenated aromatic hydrocarbons (e.g., 9,10-dihydroanthracene, 1,2,3,4-tetrahydronaphthalene... 

The proposed mechanism for these catalytic oxidations includes two catalytic redox cycles (i) initial oxidation of iodobenzene with Oxone, producing hydroxy(phenyl)iodonium ion and hydrated iodosylbenzene and (ii) the oxidation of iron(III)-porphyrin to the oxoiron(IV)-porphyrin cation-radical complex by the intermediate iodine(III) species (Scheme 4.58) [93]. The oxoiron(IV)-porphyrin cation-radical complex acts as the actual oxygenating agent toward aromatic hydrocarbons. The presence of the [PhI(OH)]+ and PhI(OH)2 species in solutions containing Phi and Oxone has been confirmed by ESI mass spectrometry [93]. 

Based on studies of the RuCls-catalyzed disproportionation of iodine(III) species to iodobenzene and iodylbenzene [53, 94-96], a mild and efficient tandem catalytic system for the oxidation of alcohols and hydrocarbons via a Ru(in)-catalyzed reoxidation of ArlO to ArI02 using Oxone as a stoichiometric oxidant has been developed [53, 96, 97]. In particular, various alcohols are smoothly oxidized in the presence of catalytic Phi and RuCls in aqueous acetonitrile at room temperature to afford the respective ketones from secondary alcohols, or carboxylic acids from primary alcohols, in excellent isolated yields (Scheme 4.59) [97]. 

Iodobenzene (2 equlv)/Oxone< (4 equiv)/ EtjN (2 equiv)... 

A mixture of Oxone (4 equiv) and iodobenzene (2 equiv.) in methanol was stirred at room temperature for 20 min followed by addition of triethylamine (2 equiv.) and the substrate (1 or 3 1 equiv.) the resulting mixture was stirred for another 40 min. On completion of the reaction, the mixture was diluted with water and then extracted twice with EtOAc. The organic layer was washed successively with 10% NaHCOa (2 x 20 mL) and H2O (2 x 20 mL), and then dried over anhyd. Na2S04, filtered, and concentrated under reduced pressure to yield the cmde product. The crude material was purified by column chromatography using petroleum ether and ethyl acetate mixture (70 30) as eluent. All the products were characterized by spectral studies. 

Patel, K. N., Jadhav, N. C., Jagadhane, P. B., and Telvekar, V. N. (2012). A novel approach strategy for the construction of azole heterocycles via an oxidative dwsulfurization approach using iodobenzene and Oxone . Synlett, 23, 1970-1972. 

Oxidative desulfurization of acylthiosemicarbazides 97 and bisdiarylthioxneas 99 involving hydroxy(phenyl) iodonium ion was effectively applied by Telvekar et al. to deliver the corresponding 2-arylaminooxadiazoles 98 and 2-arylaminothiadiazoles 100 in good-to-excellent yields. This active iodine species, hydroxy(phenyl)iodonium ion was generated by the oxidation of iodobenzene using inexpensive and readily available Oxone as a co-oxidant at room temperature (Scheme 20) [36]. 

K.N. Patel, N.C. Jadhav, P.B. Jagadhane, V.N. Telvekar, A novel strategy for the construction of azole heterocycles via an oxidative desulfurization approach using iodobenzene and oxone , Synlett 23 (2012) 1970-1972. 

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