By Debbie Dunn,2014-02-08 10:14
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Organic Syntheses, Coll. Vol. 10, p.696; Vol. 77, p.141



    [ 1,2-Benziodoxol-3(1H)-one, 1,1,1-tris(acetyloxy)-1,1-dihydro- ]

    Submitted by Robert K. Boeckman, Jr., Pengcheng Shao, and Joseph J.

    1Mullins .

    Checked by Kevin P. Minbiole and Amos B. Smith, III.

    1. Procedure

    Caution: Compounds 1 and 2 are heat- and shock-sensitive compounds,

    showing exotherms when heated (>130?C). All operations should be conducted behind an explosion shield.

    A. 1-Hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide (1) . A 2-L, three-necked,

    round-bottomed flask, fitted with a mechanical stirrer, condenser, and an immersion thermometer is charged with 80.0 g (0.48 mol) of potassium

    bromate (KBrO) and 750 mL of 2.0 M sulfuric acid (Note 1),(Note 2),(Note 3). 3

    The resulting clear solution is heated to 60?C in an oil bath and 80.0 g of finely powdered 2-iodobenzoic acid (0.323 mol) is added in 10-g portions over 40

    min (Note 4), (Note 5). The solution becomes red-orange, bromine vapor is

    evolved, and a white solid begins to separate (Note 6). After the addition is

    complete, the temperature is maintained at an internal temperature of 65?C for 2.5 hr (Note 3).

    The reaction mixture is cooled to 2-3?C in an ice-water bath, and the resulting solids are collected by vacuum filtration (Note 7), (Note 8). The filter

    cake is thoroughly washed successively with 500 mL of cold deionized water, 2 × 80 mL of absolute ethanol , and 500 mL of cold deionized water affording 88.2 g (98% of theoretical) of moist solid iodinane oxide 1 (Note 9), (Note 10).

    B. 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one (2) . A 1-L,

    three-necked, round-bottomed flask, equipped for magnetic stirring and fitted with an immersion thermometer, is charged with 88.2 g of the moist solid iodinane oxide 1 , 150 mL of glacial acetic acid , and 300 mL of acetic anhydride

    (Note 11). The flask is flushed with dry argon, and maintained under a dry argon

    atmosphere. Magnetic stirring is commenced, and the mixture is heated to 85?C (internal temperature) over 30 min by means of an oil bath, and kept at this

temperature until all the solids dissolve (20 min) to afford a colorless to clear

    yellow solution (Note 12). Heating and stirring are discontinued and the reaction mixture is allowed to cool slowly to room temperature in the oil bath for 24 hr. A large quantity of colorless crystals separate during this time (Note 13). The

    resulting crystalline solids are isolated by careful vacuum filtration in the reaction vessel under argon using a fritted adapter followed by washing the solids with three 80-mL portions of anhydrous ether and subsequent vacuum

    filtration in the reaction vessel as above (Note 14), (Note 15). Residual solvent

    is removed under vacuum affording 101.0 g (74% yield over 2 steps) of periodinane 2 as a white, free-flowing crystalline solid that is largely or completely soluble (slightly cloudy to clear solution) in chloroform and

    methylene chloride and is sufficiently pure (95%) to be suitable for use in

    oxidations (Note 16),(Note 17),(Note 18),(Note 19).

    2. Notes

    1. Although no problems with explosion of 1 or 2 have been encountered in

    the use of this procedure, prudence dictates that all operations should be

    2,34567,8conducted behind an explosion shield.

    Potassium bromate (>99.5%) was used as received from Fluka Chemical 2.


    3. Use of higher concentration sulfuric acid (2.0 M) than traditionally

    2-iodobenzoic acid to employed is crucial to allow complete conversion of the

    21. In the submitters hands, use of lower concentrations (0.5 M) of sulfuric

    acid at 60?C led to exclusive formation of

    1-hydroxy-1,2-benziodoxol-3(1H)-one. When lower concentrations of sulfuric

    acid are employed, higher temperatures are required to effect oxidation, as judged by the initiation of bromine evolution. One of the factors leading to the lack of reproducibility in the preparation of 2 results from incomplete conversion

    to 1.

    4. 2-Iodobenzoic acid (Aldrich Chemical Company, Inc.) was recrystallized from toluene (100 g/500 mL).

    5. The bromine vapors are vented by inverting a funnel over the open condenser (allowing a small gap between the funnel and the condenser top) with the stem attached to a gas washing bottle containing saturated aqueous sodium thiosulfate solution, which is in turn, connected to a water aspirator.

    6. Addition of the 2-iodobenzoic acid to the bromate-aqueous acid mixture

    results in an easily controlled, smooth reaction and an easily stirred reaction mixture. The stirring rate should be regulated such that splashing is minimized and solids do not accumulate on the walls or roof of the reaction vessel. Any solids which adhere to the sides or roof of the reaction vessel above the level of the liquid should be washed back into the reaction mixture with the minimum amount of 2M sulfuric acid. Addition of the bromate to the mixture of

    2iodobenzoic acid and sulfuric acid as originally described, led to a thick

    precipitate that was difficult to stir, and the accumulation of solid on the walls of

the reaction vessel. Given the thermal sensitivity of 1, the present procedure

    8,9appears much safer (Note 1).

    7. The reaction mixture is thoroughly cooled prior to filtration and cold water is employed for washing because of the low but appreciable solubility of 1 in

    0.3 g/100 mL). water (

    8. Use of a ceramic Büchner funnel with coarse filter paper is recommended to avoid scraping a glass frit during removal of 1. A rubber spatula is

    recommended for stirring and manipulation of the filter cake. The filter cake can be conveniently removed from the funnel by applying a small amount of air pressure to the stem.

    9. All washes were conducted by slurrying the solids on the filter bed with a rubber spatula followed by application of the vacuum. In view of the sensitivity

    34567(Note 10) of this intermediate and/or the periodinane