O-Iodoxybenzoic acid.

IODOXYBENZENE, 43, 65 o-Iodoxybenzoic acid, 43,67 4-Iodoxybiphenyl, 43,67 o-Iodoxyphenetole, 43,67 ffi-Iodoxytoluene, 43,67 a-Iodoxytoluene, 43,67 p-Iodoxytoluene, 43,67 2-Iodoxy-m-xylene, 43,67 2-Iodoxy-p-xylene, 43,67... 

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-... 

A few years later,3 it was shown that o-iodoxybenzoic acid (36)—itself a precursor in the preparation of Dess-Martin periodinane—is able to oxidize very effectively alcohols in DMSO solution. o-Iodoxybenzoic acid—normally referred to as IBX—exists mainly as a cyclic form 37, which crystallizes as a polymer with very low solubility in most solvents with the exception of DMSO. Although, IBX (36) was already known in 1893,4 this ultracentenial reagent found very little use till very recently, when awareness about its solubility in DMSO was raised. 

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... 

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. 

Oxidation of benzylic positions with o-iodoxybenzoic acid in DMSO proceeds via a similar mechanism involving the formation of benzyl radicals by SET [Eq. (89)] [164]. A variety of aromatic aldehydes were obtained in good yields with no over-oxidation to carboxylic acids. 

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]. 

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. 

Preparation of the ortho-qamont 162 from p-hydroxyacetophenone (160). This involved silylation of acetophenone, ketal protection, desilylation, and regiose-lective oxidation of phenol to o-quinone 162 using o-iodoxybenzoic acid (IBX) (Scheme 10a). 

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