Iodine Iodobenzoic Acid

The nucleophilic displacement of the iodine moiety in 2-iodoben-zoates mediated by triphenyltin hydride and di-n-butyltin dichloride in aqueous solution has been demonstrated (Eq. 6.16).33 For example, 2-iodobenzoic acid reacts with a toluene solution of Ph3SnH/l,3-(N02)2 C6H4/aq. NaHC03 to give 89% yield of salicylic acid. 

Iodine, detection of, 1041, 1042, 1043, 1045 recovery of, 647 Iodine monochloride, 974 5-Iodo-2-ammotoluene, 647 p-Iodoaniline, 647 Iodobenzene, 533, 538, 591, 598 Iodobenzene diacetate, 541 Iodobenzene dichloride, 534, 541 o-Iodobenzoic acid, 760... 

Two polyvalent iodine compounds arising from o-iodobenzoic acid have been found to be useful synthetic reagents. Thus oxidation of the iodo acid (7) with potassium persulphate, followed by the addition of benzene and treatment with potassium iodide gives the iodonium iodide (8) which is converted into diphenyliodonium-2-carboxylate [DPIC (9)] with aqueous alkali (Expt 6.35).16... 

The periodinane (10) may also be prepared from o-iodobenzoic acid by oxidation with potassium bromate and then treatment with acetic anhydride18 (see Expt 6.36 for detailed formulation). It should be noted that the organic derivatives of pentacoordinate iodine(v) are termed periodinanes.18b This compound (the systematic name is l,l,l-triacetoxy-2,l-benzoxiodol-3(3//)-one) has found use as an oxidant of primary alcohols to aldehydes and alicyclic ketones to secondary alcohols it is claimed to have advantages over the chromium-based oxidation reagents. 

The oxidation of ortho-iodobenzoic acid to give the Dess-Martin reagent is shown in Figure 17.39. This oxidation is a synthetically important oxidation of an iodine atom. The mechanism of the oxidation is not yet understood. 

Another important modern reagent (discovered in 1983) is known as the Dess-Martin periodi-nane, and is an iodine compound that can be made from 2-iodobenzoic acid, itself available from anthranilic acid via the diazonium salt route, as described in the last chapter. 

The Dess-Martin reagent (7.16) belongs to a group of compounds containing a hypervalent iodine atom. It is prepared from o-iodobenzoic acid via 7.15. 

Copper (or Cu )-Ascorblc acid. Anbar et aV found that o-iodobenzoic acid is reduced rapidly to benzoic acid by copper (II) ions and ascorbic acid in neutral aqueous solution but that reduction of p-iodobenzoic acid under the same conditions is at least 1,000 times slower. Safe and Moir effected selective reduction of the iodine atom of (1) without disturbance of the nitro group with copper metal and alkaline ascorbic acid. The method failed with the corresponding bromo compound. 

Iodoanthranilic acid has been prepared by the reduction of 2-nitro-s-iodobenzoic acid, by treatment of anthranilic add with iodine in potassium hydroxide solution, by treatment of the anhydride of s-hydroxymercurianthranilic acid with iodine in aqueous potassium iodide solution, and by iodination of anthranilic acid in glacial acetic acid solution with iodine mono-chloride. ... 

Recently, Ishihara and co-workers developed a more powerful hypervalent iodine catalyst, generated in situ from 2-iodobenzoic acid and furthermore demonstrated that its sulfonic acid analog 2 is more reactive as a precatalyst (Equation 10.3) [8]. They reported that it was not necessary to isolate hypervalent iodine compounds, which are potentially explosive oxidants, and furthermore that more powerful oxidants could be generated in situ. 

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... 

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