2-Hydroxy-5-iodobenzoic acid

Iodosalicylic acid (2-hydroxy-5-iodobenzoic acid) [119-30-2] M 264.0, m 197 pKj 2.65, pK 13.05. Crystd from water. 

The pathway by which the reactions are considered to occur involves attack of the enolate anion at the 1 0 bond of o-iodosyl benzoic acid followed by reductive elimination of o-iodobenzoic acid upon addition of methoxide to the carbonyl group. Ring opening of the epoxide thus formed yields the hydroxy dimethyl acetal ... 

Hydroxy-5-iodobenzoic acid see 5-iodosaIicylic acid. a-Hydroxyisobutyric acid see 2-hydroxy-2-methylpropionic acid. 

A. 1 -Hydroxy-1,2-benziodoxol-3(1 H)-one 1-oxide (1). A 2-L, three-necked, round-bottomed flask, fitted with a mechanical stirrer, condenser, and an immersion thermometer is charged with 80.0 g (0.48 mol) of potassium bromate (KB1O3) and 750 mL of 2.0 M sulfuric acid (Notes 1-3). The resulting clear solution is heated to 60°C in an oil bath and 80.0 g of finely powdered 2-iodobenzoic acid (0.323 mol) is added in... 

Use of higher concentration sulfuric acid ( 2.0 M) than traditionally employed is crucial to allow complete conversion of the 2-iodobenzoic acid to 1.2 In the submitters hands, use of lower concentrations ( 0.5 M) of sulfuric acid at 60°C led to exclusive formation of 1-hydroxy-1,2-benziodoxol-3(1 H)-one. When lower concentrations of sulfuric acid are employed, higher temperatures are required to effect oxidation, as judged by the initiation of bromine evolution. One of the factors leading to the lack of reproducibility in the preparation of 2 results from incomplete conversion to 1. 

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... 

The procedure was applied to several enolizable ketones with yields slightly better than those obtained with DIB. However, the main advantage of o-iodosylbenzoic acid is that its use avoids chromatographic separation the solubility of the o-iodobenzoic acid produced in alkali allows the isolation of the hydroxy dimethyl-acetals by direct extraction. For large-scale preparations the acid may be recycled. 

C7H5Br30 1,2,4-tribromo-5-methoxybenzene 95970-10-8 25.00 22119 2 10034 C7H5103 4-hydroxy-3-iodobenzoic acid 37470-46-5 25.00 1.9394 2... 

C7H5Br30 1,2,5-tribromo-3-methoxybenzene 73931-44-9 25.00 2.2119 2 10035 C7H5I03 5-hydroxy-2-iodobenzoic acid 57772-57-3 25.00 1.9394 2... 

A range of simple analogs of benzoic acid and phenylalanine, easily obtainable from standard chemical suppliers, were chosen as substrates. These included a large number of hydroxy- and dihydroxybenzoic acids, aminoben-zoic acids, nitrobenzoic acids, fluoro-, difluoro-, trifluoro-, tetrafluoro- and pentafluorobenzoic acids, chlorobenzoic acids, iodobenzoic acids, and methoxybenzoic acids. A number of structures other than those with a six-mem-bered aromatic ring were also tried, including pyridinecarboxaldehydes, alicy-clic carboxylic acids, naphthalenecarboxylic acids, furancarboxylic acids, thiophenecarboxylic acids, nitro-, bromo-, and chlorothiophenecarboxyhc acids. 

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. 

Furthermore, besides activated nickel, cobalt, and copper (see Chapter 2), indium has been proved as an effective active metal for the coupling of aryl iodides. Thus by heating an equimolar amount of indium and aryl iodides in refluxing DMF, symmetrical biaryls were furnished with high to excellent yields [78]. The indium-promoted homo-coupling reaction tolerates the presence of free hydroxy and carboxylic acid groups well. For example, 2-iodobenzoic acid (104) was converted to diphenic acid (57) in 75% yield. Scheme 22. 

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. 

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