IBX acid or 2-iodoxybenzoic acid is an organic compound used in organic synthesis as an oxidizing agent. This periodinane is especially suited to oxidize alcohols to aldehydes. The IBX acid is prepared from 2-iodobenzoic acid, potassium bromate and sulfuric acid.
The reaction mechanism for an oxidation of an alcohol to an aldehyde according the so-called hypervalent twisting mechanism involves a ligand exchange reaction replacing the hydroxyl group by the alcohol followed by a twist and a elimination reaction.
- The reaction mechanism for this glycol cleavage is based on initial formation of an adduct between 10-I-4 IBX and DMSO to an 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 presents oxidation to the acyloin competes. Trifluoroacetic acid is found to facilitate the overall reaction.
- IBX is also available as silica gel or polystyrene bound IBX. In many application IBX acid is replaced by Dess-Martin periodinane which is more soluble in common organic solvents. A sample reaction is a IBX oxidation used in the total synthesis of eicosanoid:
- 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”, Org. Synth. 77: 141; Coll. Vol. 10: 696
- 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.
- Dess, D. B.; Martin, J. C. (1991). “A Useful 12-I-5 Triacetoxyperiodinane (the Dess-Martin Periodinane) for the Selective Oxidation of Primary or Secondary Alcohols and a Variety of Related 12-I-5 Species”. Journal of the American Chemical Society 113 (19): 7277–7287. doi:10.1021/ja00019a027.
- Su, J. T.; Goddard, W. A. III (2005). “Enhancing 2-Iodoxybenzoic Acid Reactivity by Exploiting a Hypervalent Twist”. Journal of the American Chemical Society 127 (41): 14146–14147. doi:10.1021/ja054446x. PMID 16218584.
- 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.
- Mohapatra, D. K.; Yellol, G. S. (2005). “Asymmetric Total Synthesis of Eicosanoid” (pdf). Arkivoc 2005 (3): 144–155.
thanks to DR WILL WATSON OF SCIENTIFIC UPDATE ON A WARNING
Beware, IBX can explode, see C&E News, 1990, vol 68, issue 29 page 3. A stabilised non-explosive formulation of IBX mixed with benzoic acid and phthalic acid is available from Simafex, see Org. Lett., 2003, 5, 2903.