Iodoxybenzoic acid, and

The tris trifluoroacetoxy analog of Dess-Martin reagent is formed from o-iodoxybenzoic acid and trifluoroacetic anhydride. Curiously, no reports about the reactivity of this interesting oxidant are available [65]. 

Both cholestan-3-one and cholestan-3-ol yield l,4-cholestadien-3-one on treatment with iodoxybenzene or m-iodoxybenzoic acid and a catalytic amount of benzeneseleninic anhydride, which is generated in situ from diphenyldiselenide [526], The treatment of cholestan-3-one with phenyl-selenyl chloride and hydrogen peroxide gives l-cholesten-3-one [167] (equations 31 and 32). 

Hypervalent iodine(V) reagents, such as IBX (2-iodoxybenzoic acid) and DMP, have found widespread synthetic application as stoichiometric oxidants for the facile and selective oxidation of primary alcohols and secondary alcohols to the respective carbonyl compounds and for other important oxidative transformations... 

Lindel and co-workers had earlier achieved cyclization of intermediate 166 with 2-iodoxybenzoic acid (IBX, Dess-Martin periodinane) to give 167 (Equation 41), followed by subsequent dehydration and dihydroxylation of G(10)—C(10zz) to an advanced synthetic intermediate <2002TL3699>. 

Several organohypervalent iodine reagents have been used for the oxidation of alcohols and phenols such as iodoxybenzene, o-iodoxybenzoic acid (IBX), bis(trifluoroa-cetoxy)iodobenzene (BTI), and Dess-Martin periodinane etc. But the use of inexpensive iodobenzene diacetate (IBD) as an oxidant, however, has not been fully exploited. Most of these reactions are conducted in high boiling DMSO or toxic acetonitrile media that results in increased burden on the environment. 

Hypervalent iodine reagents have become extremely valuable tools in organic chemistry [121]. Reagents such as the Dess-Martin periodinane have received immense attention because of its efficiency and mild reaction conditions. The precursor to the Dess-Martin periodinane, o-iodoxybenzoic acid (IBX) has also be-... 

The electrochemical transformation of 2-methoxy- and 2-methylphenols to give orthoquinoid cyclohexadienone synthons with the aid of iodanes has been reported [173]. Iodanes (or hyperva-lent iodine [174, 175]) are a large family of reagents [176, 177] and often beneficial as clean and recyclable reagents [178]. The two most often utilized reagents are 2-Iodoxybenzoic (IBX) acid and l,l,l-triacetoxy-l,l-dihydro-l,2-benziodoxol-3(lH)-one (Dess-Martin pe-riodinane, DMP) (see Scheme 7). These... 

The o-iodoxybenzoic acid (37) (p. 181) commonly known as IBX was prepared for the first time more than a century ago by Hartman and Meyer by oxidation of o-iodobenzoic acid with KBrC>3.4 This compound was not explored in organic synthesis for a long time because it was wrongly supposed that its virtual lack of solubility in common organic solvents would preclude any synthetic usefulness. IBX came to the attention of the organic... 

Iodoxybenzene (PI1IO2) has been briefly explored in the oxidation of benzylic alcohols to benzaldehydes, giving best results with an acetic acid catalysis.120 The guanidinium salt of m-iodoxybenzoic acid is soluble in CH2C12 and able to carry out oxidative breakages of 1,2-diols.120... 

The kinetics of oxidation of Dess-Martin periodinane (DMP) and its iodoxybenzoic acid (IBX) precursor have been compared to explain their often different selectivities.152 A fast pre-equilibrium produces transient iodic esters, whose axial alkoxy structure for IBX was determined by 1H NMR spectroscopy, which then disproportionate in a rate-limiting maimer to product. As a result, steric effects in alcohol oxidation reflect a balance between opposing effects on equilibrium constants and rate constants for disproportionation. With 1,2-diols DMP gives spirobicyclic... 

Iodoxybenzoic acid. Potassium bromate (76.0 g, 0.45 mol) is added over a half-an-hour period to a vigorously stirred mixture of o-iodobenzoic acid (85.2 g, 0.34 mol) and 730 ml of 0.73 m sulphuric acid. During the addition the reaction mixture is kept below 55 °C. The mixture is warmed to 65 °C and stirred for 3.6 hours. Cooling to 0°C, filtering, and washing with 1000 ml of water and two 50-ml portions of ethanol give the product (89.1 g, 93%). 

A variety of methods have been described to solve the task in solution.16 Common oxidative agents for this transformation include various heavy-metal reagents such as chromium-or ruthenium-based oxides, pyri-dine-S03, and dimethylsulfoxide (DMSO) in combination with acetic anhydride, carbodiimide, or oxalyl chloride for activation. One of the most prominent methods for the reliable conversion of sensitive compounds is the Dess-Martin reagent or its nonacetylated equivalent, 1-hydroxy-(17/)-benzo-l,2-iodoxol-3-one-l-oxide (2-iodoxybenzoic acid, IBX). 

Oxidation of 3-hydroxymethyl-2,3-dihydro-5H-pyrido[l,2,3-cfe][1,4] benzoxazin-5-ones with o-iodoxybenzoic acid in DMSO and with Dess-Martin periodinate in CH2CI2 afforded 3-formyl derivatives (08WOP2008/ 120003). Dehydrogenation of ethyl 10-[2-(ferf-butoxycarbonyl)-l,2,3,4,6,8a-hexahydropyrrolo[l,2-a]pyrazin-7-yl]-9-fluoro-3(S)-methyl-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de][l,4]oxazine-6-carboxylates in the presence of Pd/C with air in MeOH afforded 10-[2-(ferf-butoxycarbonyl)-l, 2,3,4-tetrahydropyrrolo[l,2-a]pyrazin-7-yl] derivatives, which then were deprotected (09BML4933). 

Exposure of unsaturated anilides to o-iodoxybenzoic acid in THF-DMSO at 90°C results in cyclization to give y-lactams [Eq. (88)] [163]. A mechanism involving an intermediacy of amidyl radical 95, produced by SET and then deprotonation, was proposed for the formation of y-lactams. 

Several solid supports have been employed for the attachment of o-iodosobenzoic acid, including silica gel, titania and nylon [89]. Two polymer-supported o-iodoxybenzoic acid reagents have recently been reported. The first was obtained by attaching a carboxymethyloxy derivative of f-butyl o-iodo-benzoate to an aminopropylated silica gel and oxidation with oxone [90]. The second involved chloromethylated polystyrene which was coupled with methyl 5-hydroxy-2-iodobenzoate and eventually oxidized by Bu4NS05H/MeS03H [91]. Some of these polymeric reagents appear in Scheme 31. 

The formation of the products 43 and 45 has also been studied from a mechanistic point of view. Labeling studies with H2180 revealed that two molecules of acetyl-2-iodoxybenzoic acid (formed by the reaction between Dess-Martin Peri-odinane 8 and water) are involved in para-quinone formation. It is suspected that the substituent in 2-position in 42 blocks another molecule of acetyl-2-iodoxybenzoic acid attacking the initially formed product leading to the formation of ortho-imidoquinones. Anilides substituted in the 3-position does lead to complex mixtures in the oxidation reaction. 

Recently it was found that iodine(v) compounds like 2-iodoxybenzoic acid (IBX) 7 can be used to affect selective oxidations at carbon atoms adjacent to aromatic systems. The mechanism of this transformation is believed to proceed via a SET (Single-Electron-Transfer) process. A postulated mechanism for the oxidation of benzylic positions is outlined in Scheme 32. This oxidation is quite general and proceeds efficiently in fluorobenzene/DMSO mixtures or in DMSO at 80 °C [ 135]. Starting from compounds 70, the corresponding aldehydes 71 can be obtained easily in good yields. 

Oxidation of thiochroman-4-ol to thiochroman-4-one can be achieved without competing Pummerer rearrangement using triphenylphosphine dihalides in DMSO (Equation 92) <2002TL8355>. This oxidation has also been achieved using polymer-bound periodinane (82% yield) <1999T6785> and 2-iodoxybenzoic acid is also effective (92%) <1995JOC7272>. 

In contrast, periodinanes (i.e. iodoxo or iodine(V) reagents), preferably as the 1-hydroxy-(li-f)-benzo-l,2-iodoxol-3-one-l-oxide (2-iodoxybenzoic acid, IBX) [20, 21] or its acetylation product, the Dess-Martin reagent [22], have been widely used for oxidation of sensitive and complex alcohols. Periodinanes have not yet been prepared on a polymer support a silica-supported IBX has been reported recently [23]. 

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