Sodium Bromate


[7789-38-0]  · BrNaO3  · Sodium Bromate  · (MW 150.89)

(in combination with CAN, oxidizes alcohols to carbonyl compounds;1 oxidizes other functional groups; promotes oxidative cleavage of ethers2)

Physical Data: mp about 381 °C decomposing with evolution of oxygen; d 3.34 g cm-3.

Solubility: sol 2.5 parts water, 1.1 parts boiling water; almost insol alcohol; sodium bromate is more soluble in water than potassium bromate.

Form Supplied in: colorless crystals or white granules or powder; widely available. Drying: for analytical work dry at 100-110 °C for 1 h.

Handling, Storage, and Precautions: sodium bromate is a strong oxidizing agent (standard potential is 1.44 V); toxicity is low; should be kept from contact with mineral acids and organic compounds during storage.

Oxidation of Alcohols.

Sodium bromate, when used with catalytic amounts of cerium(IV) salts, oxidized arylmethanols to the corresponding ketones and aldehydes (eq 1).3 The sodium bromate serves to continuously replenish the more expensive oxidant, Cerium(IV) Ammonium Nitrate (CAN).

Sodium bromate was superior to other oxidants in the transition metal-catalyzed oxidation of alcohols to carbonyl compounds.1 Primary alcohols were recovered practically unchanged. Selective oxidations were observed in mixed primary/secondary alcohol systems (eq 2). However, alkenic moieties even several carbon atoms removed from the hydroxyl group interrupted the oxidation.1 Oxidations using polymer-supported CeIV, which are not affected by the alkene moiety in the substrate, provide a useful extension of this method.4

Secondary alcohols could also be oxidized using ruthenium derivatives in combination with sodium bromite.1 Oxidation of primary alcohols to aldehydes could be achieved without overoxidation using sodium bromate and dodecacarbonyltriruthenium(0) or sodium bromate and buffered Ruthenium(III) Chloride.1 Metal-catalyzed oxidation technology has recently been reviewed.5 Secondary alcohols are oxidized to ketones with Sodium Bromite in aqueous acetic acid in the absence of a metal catalyst.6 Oxidative esterification of primary alcohols to the corresponding ester occurs in good yield with sodium bromite.6

Oxidation of hydroquinone derivatives to produce the quinones has been reported with sodium bromate in acetic acid.7 Oxidations of hydroquinones using sodium bromate and CAN in the solid state8 and in solution9 have also been reported (eq 3).

Oxidation of Other Functional Groups.

The oxidation of sulfides to sulfoxides has been reviewed.10 A mixture of sodium bromate and bromide in hydrochloric acid solution, which generates a solution of bromine, oxidized sulfides to the sulfoxides.11 Potassium Bromate in the absence of added bromide also oxidized thiophenol to diphenyl disulfide or benzenesulfonic acid depending on the conditions.12 4,4-Dinitrodiphenyl sulfide was oxidized to the sulfone in excellent yield.12

Catalytic amounts of CAN and sodium bromate have been shown to oxidize diaryl sulfides and dialkyl sulfides to the corresponding sulfoxide without overoxidation to the sulfone.9 In contrast, using CAN alone, dialkyl sulfides were found to undergo the Pummerer rearrangement.13 Sodium bromite also oxidizes alkyl and aryl sulfides to the sulfoxide.6

Catalytic ring opening of epoxides has been reported using polymer-supported cerium(IV) catalysts (eq 4).14 A mixture of sodium bromate in nitric acid is used to regenerate the catalytic activity. Potassium bromate also oxidizes dialkylhydrazine derivatives to the tetraalkyltetrazenes.15 Benzaldehyde has been oxidized to benzoic acid using potassium bromate.16 However, sodium bromate and CAN were not effective for the oxidation of 1,4-dihydropyridines to the pyridine derivatives.17

Oxidative Cleavage of Ethers.18

Methyl, ethyl, trimethylsilyl, and t-butyldimethylsilyl ethers readily undergo oxidative cleavage to afford the corresponding carbonyl compounds with a catalytic amount of CAN and a molar equivalent of sodium bromate (eq 5).2 The reaction proceeds smoothly in refluxing aqueous acetonitrile. The reactivity of sodium bromate and CAN approaches that of Jones/KF (see Chromic Acid) and PDC/Me3SiCl/CH2Cl2 (see Pyridinium Dichromate) for the oxidative deprotection and oxidation of alcohols.18 The selectivity of NaBrO3/CAN for the oxidation of alcohols in the presence of silyl ethers, or the selective oxidation of primary or secondary silyl ethers, has not been extensively explored.18

A selective oxidation of a primary alcohol in the presence of a t-butyldimethylsiloxy group has been reported with sodium bromite.19

Related Reagents.

Cerium(IV) Ammonium Nitrate-Sodium Bromate.

1. (a) Kanemoto, S.; Tomioka, H.; Oshima, K.; Nozaki, H. BCJ 1986, 59, 105. (b) Tomioka, H.; Oshima, K.; Nozaki, H. TL 1982, 23, 539.
2. Olah, G. A.; Gupta, B. G. B.; Fung, A. P. S 1980, 897.
3. Ho, T.-L. S 1978, 936.
4. Kanemoto, S.; Saimoto, H.; Oshima, K.; Nozaki, H. TL 1984, 25, 3317.
5. Molander, G. A. CRV 1992, 92, 29.
6. Kageyama, T.; Ueno, Y.; Okawara, M. S 1983, 815.
7. Bartlett, P. D.; Cohen, S. G.; Cotman, J. D., Jr.; Kornblum, N.; Landry, J. R.; Lewis, E. S. JACS 1950, 72, 1003.
8. Morey, J.; Saa, J. M. T 1993, 49, 105.
9. Ho, T.-L. SC 1979, 9, 237.
10. (a) Drabowicz, J.; Mikolajczyk, M. OPP 1982, 14, 45. (b) Madesclaire, M. T 1986, 42, 5459.
11. Koenig, N. H.; Swern, D. JACS 1957, 79, 4235.
12. Adak, M. M.; Ganerjee, G. C.; Banerjee, A. JIC 1985, 62, 224.
13. Ho, T.-L.; Wong, C. M.; S 1972, 561.
14. Tamami, B.; Iranpoor, N.; Karimi Zarchi, M. A. Polymer 1993, 34, 2011.
15. McBride, W. R.; Kruse, H. W. JACS 1957, 79, 572.
16. Banerjee, A.; Banerjee, S.; Samaddar, H. JIC 1979, 56, 988.
17. Pfister, J. R. S 1990, 689.
18. Muzart, J. S 1993, 11.
19. Saito, S.; Hara, T.; Naka, K.; Hayashi, T.; Moriwake, T. SL 1992, 241.

James J. Harrison

Chevron Chemical Co., Richmond, CA, USA

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