[15481-39-7]  · C4H8Br2O2  · Bromine-1,4-Dioxane  · (MW 247.91)

(reagent for bromination of phenols,2 aromatic amines,3 a-bromination of aldehydes4 and ketones5)

Alternate Name: dioxane dibromide.

Physical Data: mp 60 °C.

Solubility: sol 1,4-dioxane, THF, and ether.

Preparative Methods: a 1:1 complex between 1,4-dioxane and bromine has been prepared and isolated on a 2 mol scale by the addition of bromine to 1,4-dioxane.6 The reagent has also been prepared in situ.3,7

Handling, Storage, and Precautions: the complex is reported to be volatile (much material was lost on drying).6 It can be stored at 0 °C. This material should only be handled in a fume hood.

Aromatic Brominations.

Bromine and 1,4-dioxane form a stable 1:1 complex, which has been referred to in the literature as dioxane dibromide. This complex is a mild brominating agent which has been used for bromination of activated aromatic systems. Yanovskaya et al. have reported2 the bromination of phenol to give p-bromophenol in 88% yield. Schlegel et al. were able to monobrominate 1,3-dimethoxybenzene in high yield (eq 1).8 In this case, reaction with bromine was reported to give a mixture of products.

Aromatic amines can be monobrominated to give the p-bromo compounds in moderate to good yields (eq 2).3 The yields are highest for tertiary amines.

The bromination of 5-hydroxybenzimidazole is reported9 to proceed at lower temperature and in higher yield with bromine-1,4-dioxane than with bromine alone (eq 3).

a-Bromination of Aldehydes and Ketones.

Bromine-1,4-dioxane is useful for the a-bromination of carbonyl compounds. Aldehydes have been brominated in moderate to good yields (eq 4).4

Hydroxy-substituted acetophenones can be brominated selectively on the alkyl side chain in good yields without aromatic bromination using this reagent (eq 5).5 A commonly used reagent for this transformation is Copper(II) Bromide. Use of bromine-1,4-dioxane has the advantage that no heavy metal waste is generated.

Other Applications.

Bromine-1,4-dioxane has also been used for the one-pot preparation of a-bromoacetals of aryl alkyl ketones,7 for the conversion of thiocarbonyl compounds to their oxygen analogs,10 for the hydrolysis of dithioacetals,10 for the oxidation of thiols to disulfides,10 and for the bromination of 1-trimethylsilylindene.11

Related Reagents.

Bromine; Bromine-t-Butylamine; N-Bromosuccinimide; Copper(II) Bromide; Phenyltrimethylammonium Perbromide; Pyridinium Hydrobromide Perbromide; 2,4,4,6-Tetrabromo-2,5-cyclohexadienone.

1. Dombrovski, A. V. RCR 1961, 30, 635.
2. Yanovskaya, L. A.; Terentyev, A. P.; Belenky JGU 1952, 22, 1635 (CA 1953, 47, 8032h).
3. Kosolapoff, G. M. JACS 1953, 75, 3596.
4. Yanovskaya, L. A.; Terentyev, A. P. JGU 1952, 22, 1639 (CA 1953, 47, 9258e).
5. Pasaribu, S. J.; Williams, L. R. AJC 1973, 26, 1327.
6. Billimoria, J. D.; Maclagan, N. F. JCS 1954, 3257.
7. Svoboda, J.; Palacek, J.; Dedek, V.; Mostecky, J. CCC 1984, 49, 1515.
8. Schlegel, D. C.; Tipton, C. D.; Rinehart Jr., K. L. JOC 1970, 35, 849.
9. Kuznetsov, Y. V.; Stolyarova, Lezina, V. P.; Smirnov, L. D. BAU 1989, 38, 1494.
10. El-Wassimy, M. T. M.; Jorgensen, K. A.; Lawesson, S. O. CS 1984, 24, 80.
11. Woell, J. B.; Boudjouk, P. JOC 1980, 45, 5213.

Bruce L. Finkelstein

E. I. DuPont de Nemours & Co., Newark, DE, USA

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