2- Iodobenzoic acid, oxidation anhydride

The closely related o-iodylbenzoic acid (IBX) and Dess-Martin oxidations have proved to be effective methods for the synthesis of peptide aldehydes (Table 7, Scheme 6) 9 38 39] 2-Iodobenzoic acid is oxidized by potassium bromate to form 2-iodylbenzoic acid (IBX), which can be used directly for IBX oxidation. IBX can be further treated with acetic anhydride and TosOH at 100 °C for 40 minutes to form the more stable Dess-Martin periodinane reagent 45 46]... 

Dehydrogenation of 3-kelo steroids. The dehydrogenation of 3-keto steroids to l,4-diene-3-ones with benzeneseleninic anhydride (8, 31) can be carried out in comparable yield by use of a process in which the benzeneseleninic anhydride is used in catalytic amounts and is continuously regenerated from diphenyl diselenide by oxidation with iodylbenzene. In practice, m-iodylbenzoic acid is a more convenient reagent, since m-iodobenzoic acid is easily recovered. 12-Keto and 12-hydroxy steroids arc oxidized by the catalytic system to A9(1 - -keto steroids in high yield. In fact, methyl desoxycholate (1) can be oxidized in this way directly to the trienedione 2 in 64% yield.1... 

Many of these iodanes are formed by oxidation of ortho-iodobenzoic acids or certain orf/zo-iodophenylated alcohols with Cl2, AcOOH, f-BuOCl, CF3OF or magnesium monoperoxyphthalate. Among A3-iodanes more important are those derived from o-iodosobenzoic acid which is obtained from the mild oxidation of o-iodobenzoic acid. An improved yield for o-iodosobenzoic acid was obtained by hydrolysis of its acetyl derivative which in turn was prepared from o-iodobenzoic acid and acetyl nitrate in acetic anhydride, at room temperature (Scheme 14) [52]. 

The search for mild oxidizing reagents that convert alcohols to aldehydes or ketones under neutral or near neutral conditions has produced a new type of reagent that contains a hypervalent iodine. Dess and Martin showed that 2-iodobenzoic acid (75) reacted with KBrOs in sulfuric acid to give a 93% yield of 76. Subsequent heating (100°C) with acetic anhydride and acetic acid produced 77 in 93% yield, the so-called Dess-Martin periodinane. This reagent converted alcohols to ketones or aldehydes, illustrated by the transformation of cyclohexanol to cyclohexanone in 90% yield, in dichloromethane at 25°C. In this particular... 

Hydroxy-l,2-benziodoxole-3(l//)-one (104) is commercially available or can be easily prepared by direct oxidation of 2-iodobenzoic acid or by basic hydrolysis of 2-(dichloroiodo)benzoic acid [232,233,274]. A more recent preparative procedure for 104 involves the oxidation of 2-iodobenzoic acid with acetyl nitrate in acetic anhydride at room temperature followed by aqueous work-up [275]. In the 1980s benziodoxole 104 and other hydroxybenziodoxoles attracted considerable research interest due to their excellent catalytic activity in the cleavage of toxic phosphates and reactive esters. This activity is explained by a pronounced O-nucleophilicity of the benziodoxole anion 105 due to the a-effect [234,272,276]. Spectroscopic and kinetic mechanistic studies indicate that the highly unstable iodoxole derivatives, such as the phosphate 107, are reactive intermediates in catalytic cleavage of phosphates, as shown for the catalytic hydrolysis of a typical substrate 106 (Scheme 2.39) [277-279]. This mechanism was proved by the synthesis and reactivity studies of the phosphate intermediate 107. 

IBX in the solid state has a three-dimensional polymeric stmcture due to strong intermolecular secondary I - O contacts and hydrogen bonding. A detailed X-ray diffraction study of IBX samples, prepared by the oxidation of 2-iodobenzoic acid with potassium bromate, revealed the presence of the powder and the macrocrystalline forms of IBX [674]. It was also noticed that the powder form of IBX is more reactive in the reaction with acetic anhydride than the macrocrystalline form and thus is more useful as the Dess-Martin periodinane precursor (Section 2.23.2). Treatment of macrocrystalline IBX with aqueous sodium hydroxide and then with hydrochloric acid can be used to convert it into the more reactive powder form [674]. 

The chemistry of X -iodanes in general has been less developed than with the X -iodanes [1102]. Significant interest in these compounds originated in 1983, when Dess and Martin reported a simple two-step preparation of the triacetate 800 via the bromate oxidation of 2-iodobenzoic acid to 2-iodoxybenzoic acid (IBX, 799) followed by heating with acetic anhydride (Scheme 3.316) [1103]. The authors have also found that the... 

JPC466, 1892B2632). An alternative preparative procedure for benziodoxole 83 involves the oxidation of 2-iodobenzoic acid with acetyl nitrate in acetic anhydride at room temperature followed by aqueous work-up (1992SC1799). 

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