1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one (2001)

[87413-09-0] C13H13IO8 (MW 424.16) (selective oxidation of primary,1 secondary,1 allylic,2 allenic,3 propargylic,4 benzylic,5 and α-fluorinated alcohols;6 monoprotected 1,2- and 1,3-diols and amino alcohols;7-10 α- and β-hydroxy ketones,11, 12 α- and β-hydroxy esters,13, 14 β-hydroxy amides,15 β-hydroxy sulfones;16 nucleosides;17 carbohydrates;18 compatible with a variety of protecting groups,19, 20 unsaturation,21, 22 basic nitrogen,23 divalent sulfur24 and selenium,25 and halogen26) Alternate Names: Dess–Martin periodinane; TAPI. Physical Data: mp 124–126 °C (dec). Solubility: appreciably sol CH2Cl2, CHCl3, MeCN, THF; effectively insol aromatic and aliphatic hydrocarbons, ether. Form Supplied in: white free-flowing moisture- and light-sensitive solid; not currently commerically available due to the potential explosion hazard (see below). Analysis of Reagent Purity: recommended methods include 1H NMR,1 and standardization by oxidation of benzyl alcohol;27 however, a typical iodimetric titration used for the standardization of peracids and other oxidants can likely also be employed. NMR data for the reagent: 1H NMR (300 MHz in CDCl3): δ 8.29 (d, J = 8.1 Hz, 2H), 8.09 (t, J = 8.1 Hz, 1H), 7.91 (t, J = 7.4 Hz, 1H), 2.32 (s, 3H), 1.99 (s, 6H); minor impurity peaks are observed at δ 8.39 (d), 8.21 (d), 8.00 (d), 7.27 (s), and 2.08 (s); 13C NMR (75 MHz in CDCl3): δ 175.7, 174.0, 166.1, 142.2, 135.8, 133.8, 131.7, 126.5, 125.9, 20.4, 20.2. Preparative Method: prepared from commercially available 2-iodobenzoic acid (recrystallized) by oxidation with Potassium Bromate in aqueous sulfuric acid at 65 °C for 3.6 h to afford the highly insoluble and sensitive (explosion hazard) hydroxyiodinane oxide 2 which is washed free of residual KBrO3 by sequential washing with water, ethanol, and then water again; vacuum filtration then affords the oxide as a moist solid (thorough drying is not recommended due to explosion hazard). This moist oxide is directly transformed to the reagent by treatment with excess Acetic Anhydride and Acetic Acid at 62 → 96 °C for ≈35 min (or until conversion is complete by analysis of an aliquot of the reaction mixture by NMR) followed by cooling for 12 h at room temperature. The solid reagent is collected by vacuum filtration under an inert atmosphere (glove bag/box or Schlenk techniques should be employed), and dried on the filter bed for 0.5 h; this affords the reagent 1 in 68–75% yield over the two steps (eqs 1 and 2).1, 27 A recent modification by Ireland recommends the use of p‐Toluenesulfonic Acid as a catalyst in the conversion of the oxide 2 to 1.28 (1) (2) Difficulties have sometimes attended the preparation of 1 for a variety of reasons, including but not limited to: (1) incomplete removal of KBrO3 and possibly Br2 during preparation of the hydroxyiodinane oxide 2; (2) incomplete or lack of removal of traces of ethanol used in washing the oxide intermediate (an obligatory process to avoid a potential explosion hazard); (3) incomplete acetylation of the oxide 2, as the presence of the monoacetoxy periodinane oxide has been implicated in the impact sensitivity shown by some but apparently not all samples of the reagent; and (4) partial or complete hydrolysis of the reagent during isolation by excessive exposure to atmospheric moisture (partial hydrolysis affords the aforementioned monoacetoxyiodinane oxide, and complete hydrolysis produces iodoxybenzoic acid, known to be explosive, which may contribute to the impact sensitivity observed).1 Purification: the reagent, when prepared properly, is sufficiently pure for use after standardization if desired. No purification method has been described. Handling, Storage, and Precautions: the reagent is a moisture- and light-sensitive material.1 While it can be handled briefly in the air, extensive exposure to moisture should be avoided. Transfers of solutions should be conducted using syringe techniques, and transfers of the solid are best done in a glove bag or box to avoid deterioration of the reagent. The pure solid reagent is stable indefinitely at room temperature when precautions are taken to avoid exposure to moisture and light.1 Storage should be in an amber bottle under an inert atmosphere or other means of protection from atmospheric moisture. Safety evaluations show that the precursor oxide is impact sensitive, and explosively decomposes when heated (>150 °C), with the onset varying with the sample. Handling the material as a moist solid appears to significantly reduce, but not completely remove, this explosion hazard. The pure periodinane has been stated to not exhibit impact sensitivity and to thermally decompose without explosion.1 An independent evaluation of typical samples prepared as above shows that, although the reagent is less sensitive than the precursor oxide, it has the potential to decompose violently when heated (>200 °C) and shows impact sensitivity, although less than the oxide precursor. Thus, prudence requires that the preparation, handling, and use of this reagent and its precursor be conducted with due care and precaution against potential explosion (use of appropriate explosion shields, etc.), particularly on a substantial scale. Nevertheless, as the following discussion will attest, the reagent has been prepared and utilized widely with only one report of an explosion,29 so that there is good cause to believe that, with appropriate precautions, the reagent can be prepared and handled safely on a normal laboratory scale.