O-Iodosylbenzoic acid

The present procedure using o-iodosylbenzoic acid is an improvement over... 

The treatment AT-carbonyl pyrrolidine derivatives with PhIO/TMSN3 (1 2) leads to a-azidonation of the pyrrolidine ring (Scheme 7) [25]. Similar results were obtained with the piperidine analogs, although product yields were much improved when iodosylbenzene was replaced with o-iodosylbenzoic acid and the reactions were conducted under reflux. Extension of the azidonation methodology to carbonyl derivatives of L-proline methyl ester was successful, although the product mixtures were generally more complex [26]. 

Benzylic, allylic, and propargylic alcohols can be oxidized by o-iodosylbenzoic acid (IBX) 7 in the presence of stabilized Wittig ylides to generate a>/3-unsaturated esters 30 in a one-pot procedure, Scheme 11. This is useful when the intermediate aldehydes are unstable and difficult to isolate [70]. 

With the exception of cyclic o-iodosylbenzoic acid (Section 12.1), unsubstituted iodosylbenzene is normally the reagent of choice. The best methods for its preparation involve hydrolysis of either (dichloroiodo)- or (diacetoxy-iodo)benzene. Both have been described but the latter is more convenient and has a better yield. 

The a-hydoxylation of ketones, accompanied by acetalization, should preferably be performed using o-iodosylbenzoic acid rather than DIB (Section 3.2.2). In fact, this type of transformation has reached Organic Syntheses status for acetophenone [4] ... 

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. 

Whereas a,/ -unsaturated ketones afforded with DIB a-hydroxy-/ -methoxy dimethylacetal derivatives (Section 3.2.2), some steroidal ketones of this kind showed a deviation when treated with o-iodosylbenzoic acid for example, 4-androstene-3,17-dione gave a mixture of two methoxy derivatives and a diene [5]. Several sulphides were oxidized efficiently to sulphoxides by o-iodosylbenzoic acid in acetic acid-sulphuric acid, at room temperature [3]. o-Iodosylbenzoic acid is an excellent reagent for the rapid, catalytic cleavage of reactive esters, especially phosphates, some of which are in stock in big quantities for use as potential nerve gases. This kind of reactivity has drawn considerable attention, and several analogues of the parent acid showed better catalytic activity among them, a series of structurally interesting pyridinium 1,5-zwitterions should be mentioned [6] ... 

The reaction of o-iodosylbenzoic acid with l-(trimethylsilyl)-2-propyne led to a reductive iodonio-Claisen rearrangement (Section 3.8.3), permitting the preparation of 2-iodo-3-prop-2-ynylbenzoic acid [7] ... 

Another silylated alkyne unexpectedly afforded an alkynyl peroxy derivative of o-iodosylbenzoic acid [8]. Generally, several cyclic and non-cyclic derivatives of the acid are known, some of which are shown below ... 

Some Further Reagents of Iodine (III) o-Iodosylbenzoic Acid and Its Derivatives. Reagents with Iodine-Oxygen Bonds. Reagents with Iodine-Nitrogen Bonds. 

The oxidation of thioethers is also performed with o-iodosylbenzoic acid in acetic acid containing some sulfuric acid as catalyst. Thus, thianthrene gives the corresponding sulfoxide and thianthrene monoxide affords only the disulfoxides, mainly the cis isomer <92SC1799>. lodosobenzene in the presence of a catalytic amount of benzeneseleninic acid also oxidized thianthrene and thianthrene... 

The synthetic scope of the Thiele-Winter reaction of quinines with acetic anhydride can be increased by the use of triflic acid (eq 46). Reaction of cyclopropylacylsilanes with triflic acid in aprotic solvent affords the corresponding cyclobutanone or 2-silyl-4,5-dihydrofuran derivatives. Triflic acid can react with o-iodosylbenzoic acid to form a hypervalent iodine reagent, which reacts with l-trimethylsilylalkymes to afford alkynyliodonium tri-flates bearing a carboxy group in high yields (eq 47). Reaction of (diacetoxyiodo)benzene [PhI(OAc)2] with excess triflic acid results in oligomerization of PhI(OAc)2. ... 

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