Dioxane dibromide

Furan reacts vigorously with chlorine and bromine at room temperature to give poly-halogenated products. Low temperature (-40 °C) reaction of furan with chlorine in dichloromethane yields mainly 2-chlorofuran and reaction of furan with dioxane dibromide at 0 °C affords 2-bromofuran in good yield. 2-Iodofuran is obtained by treatment of 2-furoic acid with iodine and potassium iodide in aqueous sodium hydroxide. 

A French patent claims the successful use of methanol for the 21-bromination of 17a-hydroxy-20-ketopregnanes as well as 21-bromination of 17-desoxy-20-ketopregnanes. This solvent has been successfully employed with dioxane dibromide as the brominating agent. 

Dimethyl-5a-cholestan-3-one, 92 Dimethylmagnesium, 86 Dimethylsulfonium methylide, 18, 113 Dioxane dibromide, 220... 

Procedures have been worked out which increased the yield of 2-bromothiophene to 78% on direct bromination in acetic acid-ether mixtures and to 67% in carbon tetraehlorided With the mild brominating agent, dioxane dibromide, quantitative yields of 2-bromothiophene are obtained. A very convenient procedure for the iodination of thiophenes consists of the acid-catalyzed (HzSOi) reaction with iodine and HIO3, giving 2-iodothiophene in 75% yieldd In contrast to the HgO method, all the iodine is utilized. 

Further papers in this section include the hydrosilylation of a-pinene and of j8-pinene, ° thiocyanation and selenocyanation of a-pinene, ° cationic polymerization of a- and /3-pinene epoxides,bromination of ( )-c/s-pinonic acid with dioxan dibromide, and straightforward myrtenol (224 R=CH20H) ° and tetrahydroperillyl alcohol syntheses from -pinene epoxide. 

Halogenation of dibenzofuran produces the 2-halo compounds. Bromina-tion can be achieved in good yield with bromine in acetic acid " or with N-bromosuccinimide in boiling carbon tetrachloride. The 2,8-dibromo compound has been made, using dioxane dibromide. Chlorination of dibenzofuran in acetic acid in the presence of iron powder can be controlled to yield the 2-chloro or the 2,8-dichloro compounds. 2-Chlorodi-benzofuran is best prepared by reaction of dibenzofuran with phosphorus pentachloride. 2-Iododibenzofuran (45%) results from treatment of dibenzofuran with iodine in boiling chloroform in the presence of nitric acid. 2,8-Diododibenzofuran is best prepared by reaction of dibenzofuran with iodine and iodic acid in aqueous acetic acid. ... 

Although bromination of thiophene in acetic acid gives good yields of 2-bromothiophene, quantitative yields are reported with dioxane dibromide (63AHC(l)l). Treatment of... 

Monobromination of these oxy compounds is difficult to achieve even at low temperatures and with low molar proportions of bromine. At - 10°C, bromine converted l-methyl-2-pyridone into a mixture of 3- and 5-bromo derivatives (1 2), but with 18% 3,5-dibromination as well. Reagents such as NBS at 10°C and dioxan dibromide were more effective giving a 1 4 ratio of 3- 5-bromo in a total yield of 56%, and a 1 1.3 ratio (with 8% dibromination) in a total yield of 81%, respectively (82CHE1284). 

Methyl-1,5-naphthyridine 1,5-dioxide (42, R=H) gave 2-bromomethyl-l, 5-naphthyridine 1,5-dioxide (42, R=Br) (dioxane dibromide 81% for further details, see original).290 See also Section 3.1.1. 

Thus, 5-nitro-2-acetylselenophene is readily brominated by dioxane dibromide, while introduction of bromine into the 4-nitro isomer requires the more drastic conditions of bromine in glacial acetic acid.114... 

Dioxane, as solvent in preparation, of 2,4-dialkylthiazoles, 184, 191 Dioxane dibromide, as bromination agent,... 

Formation of the 2-thiazoline-containing ( )-l-methoxyspirobrassinol 210 was accomplished in 90% yield from 1-methoxybrassinin 211 using dioxane dibromide in dioxane containing 0.5% water over 10 min (Scheme 83) <2002TL9489>. 

---