2-Iodoxybenzoic acid

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2-Iodoxybenzoic acid
IBXAcid.png
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2-iodoxybenzoic-acid-from-xtal-1997-3D-sf.png
Names
Preferred IUPAC name
1-Hydroxy-1λ5,2-benziodoxole-1,3-dione
Other names
1-Hydroxy-1λ3,2-benziodoxol-3(1H)-one 1-oxide
Identifiers
3D model (JSmol)
976364
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.157.592 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C7H5IO4/c9-7-5-3-1-2-4-6(5)8(10,11)12-7/h1-4H,(H,10,11) Yes check.svgY
    Key: CQMJEZQEVXQEJB-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C7H5IO4/c9-7-5-3-1-2-4-6(5)8(10,11)12-7/h1-4H,(H,10,11)
    Key: CQMJEZQEVXQEJB-UHFFFAOYAL
  • O=C1OI(=O)(O)c2ccccc12
  • c1ccc2c(c1)C(=O)OI2(=O)O
Properties
C7H5IO4
Molar mass 280.02 g/mol
Melting point 233 °C (decomposes)
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H314, H315, H319, H335
P260, P261, P264, P271, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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2-Iodoxybenzoic acid (IBX) is an organic compound used in organic synthesis as an oxidizing agent. This periodinane is especially suited to oxidize alcohols to aldehydes. IBX is most often prepared from 2-iodobenzoic acid and a strong oxidant such as potassium bromate and sulfuric acid, [1] or more commonly, oxone. One of the main drawbacks of IBX is its limited solubility; IBX is insoluble in many common organic solvents. IBX is an impact- and heat-sensitive explosive (>200°C). [2] Commercial IBX is stabilized by carboxylic acids such as benzoic acid and isophthalic acid.

Contents

Preparation

IBX can be prepared in a single step by adding an excess of Oxone to an aqueous solution of 2-iodobenzoic acid. After warming the solution to 70°C for three hours, the precipitated IBX is collected as a white crystalline solid (80% yield, ≥95% purity). Decomposition of IBX to 2-iodosobenzoic acid and 2-iodobenzoic acid occurs at elevated temperatures, and therefore purification by recrystallization from water is not possible. Purity can be increased (≥99%) by shorting the reaction time to one hour at 70°C, at the cost of slightly reducing yield to 77%. [2]

IBX Preparation from 2-iodobenzoic acid and Oxone. IBX Preparation.png
IBX Preparation from 2-iodobenzoic acid and Oxone.

Reaction mechanism

The reaction mechanism for an oxidation of an alcohol to an aldehyde according to the hypervalent twisting mechanism [3] involves a ligand exchange reaction replacing the hydroxyl group by the alcohol followed by a twist and an elimination reaction. The twist is a requirement because the iodine to oxygen double bond is oriented out of plane with the alkoxy group and the concerted elimination would not be able to take place. This twist reaction is a rearrangement in which the oxygen atom is moved into a proper plane for a 5 membered cyclic transition state in the elimination reaction and is calculated by Computational chemistry to be the rate-determining step in the oxidation. The twist mechanism also explains why oxidation is faster for larger alcohols than for small alcohols. The twist is driven forward by the steric hindrance that exists between the ortho hydrogen atom and the protons from the alkoxy group and larger alkoxy groups create larger steric repulsion. The same computation predicts a much faster reacting IBX derivative with a 100 fold reaction rate when this ortho hydrogen atom is replaced by a methyl group thus facilitating the twist until the elimination reaction takes prevalence as the rate determining step.

The hypervalent twisting mechanism during conversion of methanol to formaldehyde: a) ligand exchange reaction (activation energy 9.1 kcal/mol (38 kJ/mol), b) hypervalent twist 12.1 kcal/mol (51 kJ/mol), c) elimination 4.7 kcal/mol (20 kJ/mol)). IBX-Oxidation 2a.svg
The hypervalent twisting mechanism during conversion of methanol to formaldehyde: a) ligand exchange reaction (activation energy 9.1 kcal/mol (38 kJ/mol), b) hypervalent twist 12.1 kcal/mol (51 kJ/mol), c) elimination 4.7 kcal/mol (20 kJ/mol)).

IBX exists as two tautomers, one of which is the carboxylic acid. The acidity of IBX which has been determined in water (pKa 2.4) and DMSO (pKa 6.65) [4] is known to affect organic reactions, for instance acid-catalyzed isomerization accompanying oxidations.

Scope

IBX is also available as silica gel or polystyrene bound IBX. In many applications, IBX is replaced by Dess–Martin periodinane which is more soluble in common organic solvents. A sample reaction is an IBX oxidation used in the total synthesis of eicosanoid: [5] More and Finney [6] and Van Arman [7] have demonstrated that common organic solvents are suitable for many IBX oxidations, despite its low solubility, and in fact may simplify product purification.

IBX oxidation of alcohol to aldehyde, 94% chemical yield (Mohapatra, 2005) IBXacid example.svg
IBX oxidation of alcohol to aldehyde, 94% chemical yield (Mohapatra, 2005)

In 2001, K. C. Nicolaou and co-workers published a series of papers in the Journal of the American Chemical Society demonstrating, among other transformations, the use of IBX to oxidize primary and secondary benzylic carbons to aromatic aldehydes and ketones, respectively. [8]

Oxidative cleavage

IBX is notable for oxidizing vicinal diols (or glycols) to diketones without cleavage of the carbon-carbon bond, [9] but oxidative cleavage of glycols to two aldehydes or ketones can occur when modified conditions are used (elevated temperatures or trifluoroacetic acid solvent). [10]

IBX oxidative cleavage.png

The reaction mechanism for this glycol cleavage is based on initial formation of an adduct between 10-I-4 IBX and DMSO to a 12-I-5 intermediate 3 in which DMSO acts as a leaving group for incoming alcohol 4 to intermediate 5. One equivalent of water is split off forming 12-I-5 spirobicyclic periodinane 6 setting the stage for fragmentation to 7. With hydroxyl alpha protons present, oxidation to the acyloin competes. Trifluoroacetic acid is found to facilitate the overall reaction.

IBX DMSO oxidative cleavage.png

α-Hydroxylations

Kirsch and co-workers were able to hydroxylate keto compounds with IBX in α-position under mild conditions. [11] This method could be extended to β-keto esters. [12]

Oxidation of β-hydroxyketones to β-diketones

Bartlett and Beaudry discovered that IBX is a valuable reagent for the transformation of β-hydroxyketones to β-diketones. IBX provides yields superior to both the Swern and Dess–Martin oxidation protocols. [13]

Related Research Articles

<span class="mw-page-title-main">Ketone</span> Organic compounds of the form >C=O

In organic chemistry, a ketone is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH3)2CO. Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.

<span class="mw-page-title-main">Aldehyde</span> Organic compound containing the functional group R−CH=O

In organic chemistry, an aldehyde is an organic compound containing a functional group with the structure R−CH=O. The functional group itself can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are a common motif in many chemicals important in technology and biology.

In organic chemistry, the Swern oxidation, named after Daniel Swern, is a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine. It is one of the many oxidation reactions commonly referred to as 'activated DMSO' oxidations. The reaction is known for its mild character and wide tolerance of functional groups.

<span class="mw-page-title-main">Dess–Martin periodinane</span> Chemical reagent

Dess–Martin periodinane (DMP) is a chemical reagent used in the Dess–Martin oxidation, oxidizing primary alcohols to aldehydes and secondary alcohols to ketones. This periodinane has several advantages over chromium- and DMSO-based oxidants that include milder conditions, shorter reaction times, higher yields, simplified workups, high chemoselectivity, tolerance of sensitive functional groups, and a long shelf life. However, use on an industrial scale is made difficult by its cost and its potentially explosive nature. It is named after the American chemists Daniel Benjamin Dess and James Cullen Martin who developed the reagent in 1983. It is based on IBX, but due to the acetate groups attached to the central iodine atom, DMP is much more reactive than IBX and is much more soluble in organic solvents.

<span class="mw-page-title-main">Periodinane</span>

Periodinanes also known as λ5-iodanes are organoiodine compounds with iodine in the +5 oxidation state. These compounds are described as hypervalent because the iodine center has more than 8 valence electrons.

<span class="mw-page-title-main">Quinoxaline</span> Chemical compound

A quinoxaline, also called a benzopyrazine, in organic chemistry, is a heterocyclic compound containing a ring complex made up of a benzene ring and a pyrazine ring. It is isomeric with other naphthyridines including quinazoline, phthalazine and cinnoline. It is a colorless oil that melts just above room temperature. Although quinoxaline itself is mainly of academic interest, quinoxaline derivatives are used as dyes, pharmaceuticals, and antibiotics such as olaquindox, carbadox, echinomycin, levomycin and actinoleutin.

The Corey–Kim oxidation is an oxidation reaction used to synthesize aldehydes and ketones from primary and secondary alcohols. It is named for American chemist and Nobel Laureate Elias James Corey and Korean-American chemist Choung Un Kim.

Glycol cleavage is a specific type of organic chemistry oxidation. The carbon–carbon bond in a vicinal diol (glycol) is cleaved and instead the two oxygen atoms become double-bonded to their respective carbon atoms. Depending on the substitution pattern in the diol, these carbonyls will be ketones and/or aldehydes.

Ruthenium tetroxide is the inorganic compound with the formula RuO4. It is a yellow volatile solid that melts near room temperature. It has the odor of ozone. Samples are typically black due to impurities. The analogous OsO4 is more widely used and better known. It is also the anhydride of hyperruthenic acid (H2RuO5). One of the few solvents in which RuO4 forms stable solutions is CCl4.

<span class="mw-page-title-main">Lead(IV) acetate</span> Organometallic compound (Pb(C2H3O2)4)

Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula Pb(C2H3O2)4. It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically stored with additional acetic acid. The compound is used in organic synthesis.

Oppenauer oxidation, named after Rupert Viktor Oppenauer, is a gentle method for selectively oxidizing secondary alcohols to ketones.

Unlike its lighter congeners, the halogen iodine forms a number of stable organic compounds, in which iodine exhibits higher formal oxidation states than -1 or coordination number exceeding 1. These are the hypervalent organoiodines, often called iodanes after the IUPAC rule used to name them.

<span class="mw-page-title-main">Dess–Martin oxidation</span> Chemical reaction

The Dess–Martin oxidation is an organic reaction for the oxidation of primary alcohols to aldehydes and secondary alcohols to ketones using Dess–Martin periodinane. It is named after the American chemists Daniel Benjamin Dess and James Cullen Martin who developed the periodinane reagent in 1983.

Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids.

<span class="mw-page-title-main">Oxoammonium-catalyzed oxidation</span>

Oxoammonium-catalyzed oxidation reactions involve the conversion of organic substrates to more highly oxidized materials through the action of an N-oxoammonium species. Nitroxides may also be used in catalytic amounts in the presence of a stoichiometric amount of a terminal oxidant. Nitroxide radical species used are either 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) or derivatives thereof.

Fétizon oxidation is the oxidation of primary and secondary alcohols utilizing the compound silver(I) carbonate absorbed onto the surface of celite also known as Fétizon's reagent first employed by Marcel Fétizon in 1968. It is a mild reagent, suitable for both acid and base sensitive compounds. Its great reactivity with lactols makes the Fétizon oxidation a useful method to obtain lactones from a diol. The reaction is inhibited significantly by polar groups within the reaction system as well as steric hindrance of the α-hydrogen of the alcohol.

The Criegee oxidation is a glycol cleavage reaction in which vicinal diols are oxidized to form ketones and aldehydes using lead tetraacetate. It is analogous to the use of periodate but uses a milder oxidant. This oxidation was discovered by Rudolf Criegee and coworkers and first reported in 1931 using ethylene glycol as the substrate.

<span class="mw-page-title-main">Ynone</span> Organic compounds of the form RC≡CC(=O)R’

In organic chemistry, an ynone is an organic compound containing a ketone functional group and a C≡C triple bond. Many ynones are α,β-ynones, where the carbonyl and alkyne groups are conjugated. Capillin is a naturally occurring example. Some ynones are not conjugated.

Sulfonium-based oxidations of alcohols to aldehydes summarizes a group of organic reactions that transform a primary alcohol to the corresponding aldehyde (and a secondary alcohol to the corresponding ketone). Selective oxidation of alcohols to aldehydes requires circumventing over-oxidation to the carboxylic acid. One popular approach are methods that proceed through intermediate alkoxysulfonium species (RO−SMe+
2X-, e.g. compound 6) as detailed here. Since most of these methods employ dimethylsulfoxide (DMSO) as oxidant and generate dimethylsulfide, these are often colloquially summarized as DMSO-oxidations. Conceptually, generating an aldehyde and dimethylsulfide from an alcohol and DMSO requires a dehydrating agent for removal of H2O, ideally an electrophile simultaneously activating DMSO. In contrast, methods generating the sulfonium intermediate from dimethylsulfide do not require a dehydrating agent. Closely related are oxidations mediated by dimethyl selenoxide and by dimethyl selenide.

The Stahl oxidation is a copper-catalyzed aerobic oxidation of primary and secondary alcohols to aldehydes and ketones. Known for its high selectivity and mild reaction conditions, the Stahl oxidation offers several advantages over classical alcohol oxidations.

References

  1. ↑ Boeckman, R. K. Jr.; Shao, P.; Mullins, J. J. (2000). "Dess–Martin periodinane: 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one" (PDF). Organic Syntheses . 77: 141; Collected Volumes, vol. 10, p. 696.
  2. 1 2 Frigerio, M.; Santagostino, M.; Sputore, S. (1999). "A User-Friendly Entry to 2-Iodoxybenzoic Acid (IBX)". Journal of Organic Chemistry . 64 (12): 4537–4538. doi:10.1021/jo9824596.
  3. ↑ Su, J. T.; Goddard, W. A. III (2005). "Enhancing 2-Iodoxybenzoic Acid Reactivity by Exploiting a Hypervalent Twist" (PDF). Journal of the American Chemical Society . 127 (41): 14146–14147. doi:10.1021/ja054446x. PMID   16218584.
  4. ↑ Gallen, M. J.; Goumont, R.; Clark, T.; Terrier, F.; Williams, C. M. (2006). "o-Iodoxybenzoic Acid (IBX): pKa and Proton-Affinity Analysis". Angewandte Chemie International Edition . 45 (18): 2929–2934. doi: 10.1002/anie.200504156 . PMID   16566050.
  5. ↑ Mohapatra, D. K.; Yellol, G. S. (2005). "Asymmetric Total Synthesis of Eicosanoid". Arkivoc . 2005 (3): 144–155. doi: 10.3998/ark.5550190.0006.316 . hdl: 2027/spo.5550190.0006.316 .
  6. ↑ More, J.D.; Finney, N.S. (2002). "A Simple and Advantageous Protocol for the Oxidation of Alcohols with o-Iodoxybenzoic Acid (IBX)". Organic Letters. 4 (17): 3001–3003. doi:10.1021/ol026427n. PMID   12182609.
  7. ↑ Van Arman, S (2009). "2-Methyl-2-propanol as solvent for o-iodoxybenzoic acid (IBX) oxidation of 1˚ alcohols to aldehydes". Tetrahedron Letters. 50 (33): 4693–4695. doi:10.1016/j.tetlet.2009.06.045.
  8. ↑ Nicolaou, K. C.; Montagnon, T.; Baran, P. S.; Zhong, Y.-L. (2002-03-01). "Iodine(V) Reagents in Organic Synthesis. Part 4. o-Iodoxybenzoic Acid as a Chemospecific Tool for Single Electron Transfer-Based Oxidation Processes". Journal of the American Chemical Society. 124 (10): 2245–2258. doi:10.1021/ja012127+. ISSN   0002-7863. PMID   11878978.
  9. ↑ Frigerio, M.; Santagostino, M. (1994). "A Mild Oxidizing Reagent for Alcohols and 1,2-Diols: o-Iodoxybenzoic Acid (IBX) in DMSO". Tetrahedron Letters . 35 (43): 8019–8022. doi:10.1016/0040-4039(94)80038-3.
  10. ↑ Moorthy, J. N.; Singhal, N.; Senapati, K. (2007). "Oxidative Cleavage of Vicinal Diols: IBX can do what Dess–Martin Periodinane (DMP) can". Organic & Biomolecular Chemistry. 5 (5): 767–771. doi:10.1039/b618135j. PMID   17315062.
  11. ↑ Kirsch, S. F. (2005). "IBX-Mediated α-Hydroxylation of α-Alkynyl Carbonyl Systems. A Convenient Method for the Synthesis of Tertiary Alcohols". Journal of Organic Chemistry. 70 (24): 10210–10212. doi:10.1021/jo051898j. PMID   16292876.
  12. ↑ Kirsch, S. F.; Duschek, A. (2009). "Novel Oxygenations with IBX". Chemistry: A European Journal. 15 (41): 10713–10717. doi:10.1002/chem.200901867. PMID   19760735.
  13. ↑ Bartlett, S.L.; Beaudry, C.M. (2011). "High Yielding Oxidation of β-Hydroxyketones to β-Diketones Using o-Iodoxybenzoic Acid". Journal of Organic Chemistry. 76 (23): 9852–9855. doi:10.1021/jo201810c. PMID   22023037.
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