Iodine acetate bromine compounds

The most important of the halogenated derivatives of acetic acid is chloroacetic acid. Fluorine, chlorine, bromine, and iodine derivatives are all known, as are mixed halogenated acids. For a discussion of the fluorine derivatives see Fluorine compounds, organic. 

Treatment of pyrrole, 1-methyl-, 1-benzyl- and 1-phenyl-pyrrole with one mole of A -bromosuccinimide in THF results in the regiospecific formation of 2-bromopyrroles. Chlorination with IV-chlorosuccinimide is less selective (8UOC2221). Bromination of pyrrole with bromine in acetic acid gives 2,3,4,5-tetrabromopyrrole and iodination with iodine in aqueous potassium iodide yields the corresponding tetraiodo compound. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Dimethyl tricyclo[4.2.2.02 -5]deca-3,7-diene-9,10-dicarboxylate adds bromine and iodine only to the less hindered double bond to give the syn 1,2-addition product of the cyclobutene moiety79. The product composition from this compound depends on the temperature and the solvent. At high temperatures, the 1,2-addition predominates over the transannular reaction, but this predominance is small in a solvent like chloroform and is lost in a protic solvent such as acetic acid (equation 47). 

The natural glucocorticoid is hydrocortisone (cortisol). Semi-synthetic 9a-bromohydrocortisone 21-acetate was found to be less active as an anti-inflammatory agent than hydrocortisone 21-acetate by a factor of three, and 9a-iodohydrocortisone 21-acetate was also less active by a factor of 10. However, 9a-fluorohydrocortisone 21-acetate (fludrocortisone acetate) was discovered to be about 11 times more active than hydrocortisone acetate. Although the bromination sequence shown is equally applicable to chlorine and iodine compounds, fluorine must be introduced indirectly by the P-epoxide formed by base treatment of the 9a-bromo-lip-hydroxy analogue. 

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. ... 

If the 5-position is occupied, halogenation takes place in the 7-position. Bromination of 5-chloro or 5-methylisatin leads to the corresponding 7-bromo compounds,21,209 and reaction of 4-chloro-5-methoxyisatin with AT,AT-dichlorourethane in refluxing acetic acid gave 4,7-dichloro-5-methoxyisatin.138 In aqueous acetic acid these latter reactants gave 1,4-dichloro-5-methoxyisatin.136 Attempts to introduce a second iodine in 5-iodoisatin led to the isolation of 51, which could be... 

An earlier report51 that phenanthridone is brominated at C-2 on treatment with bromine in acetic acid has been confirmed291 chlorination (molecular chlorine) and iodination (iodine-iodate) in acetic acid give the corresponding 2-halogeno compounds in excellent yield.291 The bromination of 2-acetamidophenanthridone has also been described, although the orientation was not established with certainty.291... 

A systematic study of substitution reactions of oxazole itself has not been reported. Bromination of 2-methyl-4-phenyloxazole or 4-methyl-2-phenyloxazole with either bromine or NBS gave in each case the 5-bromo derivative, while 2-methyl-5-phenyloxazole was brominated at C(4). Mercuration of oxazoles with mercury(II) acetate in acetic acid likewise occurs at C(4) or C(5), depending on which position is unsubstituted 4,5-di-phenyloxazole yields the 2-acetoxymercurio derivative. These mercury compounds react with bromine or iodine to afford the corresponding halogenooxazoles in an electrophilic replacement reaction (81JHC885). Vilsmeier-Haack formylation of 5-methyl-2-phenyloxazole with the DMF-phosphoryl chloride complex yields the 4-aldehyde. 

Chlorination by sulfuryl chloride occurs at position 3 for l-oxa-6,6aA4-dithiapentalenes (71AHC(13)161, p. 181). Bromination of l,6-dioxa-6aA4-thiapentalene occurs readily and leads to the 3,4-dibromo derivative. With the same compound, iodine and silver acetate give the 3-iodo and the 3,4-diiodo derivatives (72CC1283). 

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