Alcohols 2-iodoxybenzoic acid

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. 

IODOXYBENZOIC ACID (IBX)//i-Bu4NBr/CH2Cl2-H20 A MILD SYSTEM FOR SELECTIVE OXIDATION OF SECONDARY ALCOHOLS... 

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. 

Iodoxybenzene (PI1IO2) has been briefly explored in the oxidation of benzylic alcohols to benzaldehydes, giving best results with an acetic acid catalysis.120 The guanidinium salt of m-iodoxybenzoic acid is soluble in CH2C12 and able to carry out oxidative breakages of 1,2-diols.120... 

The kinetics of oxidation of Dess-Martin periodinane (DMP) and its iodoxybenzoic acid (IBX) precursor have been compared to explain their often different selectivities.152 A fast pre-equilibrium produces transient iodic esters, whose axial alkoxy structure for IBX was determined by 1H NMR spectroscopy, which then disproportionate in a rate-limiting maimer to product. As a result, steric effects in alcohol oxidation reflect a balance between opposing effects on equilibrium constants and rate constants for disproportionation. With 1,2-diols DMP gives spirobicyclic... 

In contrast, periodinanes (i.e. iodoxo or iodine(V) reagents), preferably as the 1-hydroxy-(li-f)-benzo-l,2-iodoxol-3-one-l-oxide (2-iodoxybenzoic acid, IBX) [20, 21] or its acetylation product, the Dess-Martin reagent [22], have been widely used for oxidation of sensitive and complex alcohols. Periodinanes have not yet been prepared on a polymer support a silica-supported IBX has been reported recently [23]. 

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. ... 

From alcohols or ketones via oxidation with o-iodoxybenzoic acid (IBX) HO... 

Liu Z, Chen ZC, Zheng QG (2003) Mild oxidation of alcohols with o-iodoxybenzoic acid (IBX) in ionic hquid l-buthyl-3-methyl-imidazolium chloride and water. Org Lett 5 3321-3323... 

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). 

Organohypervalent iodine reagents such as iodoxybenzene, o-iodoxybenzoic acid (IBX), bis(trifluoroacetoxy)iodobenzene (BTI), and Dess-Marhn periodinane have been used for the oxidation of alcohols and phenols. Most of these reactions are conducted in high-boiling DMSO or relahvely toxic acetonitrile, which increase the burden on the environment. Further, the use of inexpensive iodobenzene diacetate (IBD) as an oxidant has not been fully exploited. Varma et al. have reported the first use of supported iodobenzene diacetate as an oxidant. In this novel oxidative protocol, alumina-supported IBD under solvent-free conditions rapidly converts alcohols to the corresponding carbonyl compounds in almost quantitative yields. The use of alumina as a support improved the yields markedly as compared to neat IBD (Scheme 2.2-40). 1,2-Benzenedimethanol, however, undergoes cyclization to afford l(3H)-isobenzofuranone [116]... 

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. 

In a one-pot oxidation-heteroannulation process, pyrimidines 513 were synthesized from propargylic alcohols and benzamidine or acetamidines in the presence of o-iodoxybenzoic acid (IBX) or Mn02 under MWI conditions within 40 min (Scheme 99). The yields (61-84%) were higher than those (30-69%) after heating under reflux (03SL1443). 

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-... 

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