Benzene 1,3,5-tribromo

Allyloxy)-1,3,5-tribromobenzene Allyl 2,4,6-tribromophenyl ether Benzene, 1,3,5-tribromo-2-(2-prop-enyloxy)- EINECS 221-913-2 Ether, allyl 2,4,6-trlbromo-phenyl NSC 35767 TBP-AE 2,4,6-... 

Of considerable interest is a reaction of monoarylazo derivatives of B10Hio containing electron-withdrawing substituents in the benzene ring (e.g., 2,4,6-Br3, 4-N02), which was subsequently found by Leyden and Hawthorne (1973, 1975). If the azo coupling system mentioned above (acetonitrile, - 35 °C) is allowed to come to room temperature and is treated with excess sodium propionate, the 1-diazonio-B10H9 anion and the corresponding benzene derivative are formed in considerable yield (52% with the 2,4,6-tribromo derivative as shown in Scheme 12-85). 

Bromination and nitration of substituted 1,2-selenazoles occurs at the 4-position but products undergo decomposition. 3-Methyl-5-phenyl-l,2-selenazole reacts with a mixture of concentrated nitric and sulfuric acids to give 3-methyl-4-nitro-5-(4-nitrophenyl)-l,2-selenazole in 54% yield, accompanied by other nitroderivatives. Bromination and nitration of 1-benzo-1,2-selenazoles results in substitution in the benzene ring and does not occur at the 3-position thus nitration afforded an almost equimolar mixture of 5-nitro- and 7-nitro-l-benzo-l,2-selenazoles in an overall quantitative yield, while bromination led to a mixture of mono-, di-, and tribromo compounds [2, 10]. 

The trisethers derived from l,3,5-tribromo-2,4,6-tris(bromomethyl)benzene by reaction with 2-alkenols in the presence of NaH undergo a triannulation reaction by way of a triple intramolecular Heck reaction to yield 3,7,ll-trioxa-l,2,3,4,5,6,7,8,9,10,ll,12-dodecahydro-triphenylenes <02JOC8280>. 

Benzene does not react with bromine except with Lewis acid catalysis. Phenols react in a very different manner no Lewis acid is needed, the reaction occurs very rapidly, and the product contains three atoms of bromine in specific positions. All that needs to be done is to add bromine dropwise to a solution of phenol in ethanol. Initially, the yellow colour of the bromine disappears but, if, when the colour just remains, water is added, a white precipitate of 2,4,6-tribromo phenol is formed. 

Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]). Bromination of aniline yields the tribromo derivative in Step [3]. 

Problem 23.15 Outline the synthesis from benzene or toluene of the following compounds w-nitrotoluene, m-iodotoluene, 3,5-dibromotoluene, 1,3,5-tribromo-benzene, the three toluic acids (CHJQH4COOH). the three methylphenols (cresols). 

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