Aldehydes alcohol oxidations, 2-iodoxybenzoic acid

One step oxidation of alcohols or ketones to enones (see also Saegusa) selective oxidation of benzylic groups (methyl to aldehydes) by o-iodoxybenzoic acid (IBX). 

One example is Swern oxidation, which uses oxalyl chloride and DMSO and is particularly suitable for the selective oxidation of alcohols to aldehydes or ketones. The disadvantages of this oxidation method are the need for low temperatures, the smell of the dimethyl sulfide formed and the possible oxidation of other heteroatoms. Dess-Martin periodinane (DMP, 5) or iodoxybenzoic acid (IBX, 6) are also common oxidizing agents. The main advantage of these two methods is the short reaction time at room temperature. However, typical problems are the low solubility of IBX and the formation of byproducts. In this context, Finney et al. have reported an interesting procedure avoiding these problems by a variation of the temperature IBX is sufficiently soluble in solvents such as ethyl acetate or dichloromethane at elevated temperatures, whereas it is insoluble in these solvents at room temperature. Because of this, the remaining IBX as well as the IBX-derived byproducts can be separated from the reaction mixture by simple filtration. These reisolated IBX byproducts can then be reoxidized and reused. 

The following Swern oxidation is an inexpensive, mild and fast transformation. It provides aldehydes starting from primary alcohols in the absence of water, exclusively. Other mild oxidation methods for the formation of aldehydes are known Dess-Martin periodinane (DMP), o-iodoxybenzoic acid (IBX), chromium(III) reagents, tetramethylpiperidine 7V-oxide and sodium hypochlorite (TEMPO/NaOCl), tetrapropylammonium perruthenate and N-methylmorpholine 7V-oxide (TPAP/NMO), " and palladium(II)-catalyzed oxidations are reported. ... 

A popular oxidizing agent that effects rapid oxidation of primary or secondary alcohols to aldehydes or ketones is the Dess-Martin reagent. This is the hypervalent iodine(V) compound 46, prepared from 2-iodoxybenzoic acid 45 (IBX) (6.40). Both IBX and the Dess-Martin reagent are potentially explosive and should be handled with care. 

Oxidation of Alcohols to Aldehydes and Ketones. Hyper-valent iodine compounds have powerful oxidizing capabilities. However, IBX possesses different properties than many similar oxidants, such as the related analogs iodoxybenzene and m-iodoxybenzoic acid. Until recently, the major application of IBX was its use in DMSO for the oxidation of primary alcohols to aldehydes at room temperature, without the danger of over-oxidation to carboxylic acids. The related iodo-oxy reagents oxidize benzyl alcohols to benzaldehydes at elevated temperatures in benzene (80 °C, 5-10 h) or in acetic acid (rt, 24 h), while IBX oxidizes the same compounds in 15 min (or less) at room temperature. IBX is equally effective for the oxidation of secondary alcohols to ketones under analogous conditions. Even sterically hindered alcohols are readily oxidized. Bomeol undergoes smooth oxida-... 

In the o-iodoxybenzoic acid oxidation of aryl, allyl, and alkyl alcohols to the corresponding aldehydes, the preferential catalysis of reactions of the unsaturated alcohols by cucurbit[8]uril (69) has been related to the electron density and reactivity of an intermediate stabilized a-carbanion. ... 

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