Acetone 1,1,1,3-tetrabromo

Sulfonation (66JOC565) or nitration (74JOC1157) of the acridizinium (benzo[Z ]quin-olizinium) ion (3) occurs at position 10 (Scheme 31). When acridizinium bromide is dissolved in liquid bromine and allowed to stand for 15 h the perbromide salt of 7,8,9,10-tetrabromo-7,8,9,10-tetrahydroacridizinium ion is formed and this is easily converted to the simple bromide by the action of acetone. If the tetrabromo salt is refluxed in xylene, it is reconverted to acridizinium bromide (3) in good yield. Treatment of the tetrabromide with sodium acetate gives 10-bromoacridinium bromide (Scheme 32). 

When the chlorine in the first-mentioned preparation of tetrachloroselenophene is replaced by bromine, a vigorous reaction occurs and hydrogen bromide is liberated. After twenty-four hours the solution is washed with dilute sodium hydroxide solution and with water, then evaporated on the water-bath. The brown residue, after crystallisation from alcohol, gives the tetrabromo-compound as a white, finely crystalline substance, M.pt. 102° C., wThich does not reduce permanganate in acetone solution, but slowly deposits selenium on boiling with water. 

The dimethyl ester of 3,4-dimethyl-2,5-thiophenedicarboxylic acid (377) was converted into 4,6-dicyano-l//,3//-thieno[3,4-c]thiophene (379) via the known intermediate (378) <64JOCl9l9>. Compound (379) was tetrabrominated photochemically, leading to 4,6-dicyano-l,l,3,3-tetrabromo-1 //,3//-thieno[3,4-c]thiophene (380), which lost bromine upon heating in DMF, or with sodium iodide in acetone to give l,3-dibromo-4,6-dicyanothieno[3,4-c]thiophene (164) (94JOC2223) (Scheme 33). 

Reaction of styrene with the commercially available 2,4-dibromopentan-3-one (52) in the presence of a stoichiometric amount of Fc2(CO)9 gives a 65% yield of cyclopentanone (53) as a mixture of two dia-stereoisomers (equation 44). The cycloadduct is formed in a stepwise fashion via electrophilic attack of the incipient (oxyallyl)Fe complex (54) on the alkene to form the zwitterionic species (55). Ring closure of this intermediate affords the cyclopentanone product (equation 45). In light of this mechanism, it is not surprising tl.at the reaction is highly chemoselective, i.e. only electron-rich alkenes will participate in the cycloaddition. One is also limited to alkyl-substituted oxyallyl systems since both a,a -dibromo- and a,a,a, a -tetrabromo-acetone fail to yield any cycloadduct. Fe2(CO)9 is the most efficient reagent, although Fe(CO)s can also be used. The dibromo ketones are either commercially available or easily prepared by simple procedures. ... 

Tetrabromoethane s-Tetrabromoethane. See Tetrabromoethane 2,4,5,7-Tetrabromo-3,6-fluorandiol. See D C Red No. 21 Solvent red 43 Tetrabromofluorescein 2, 4, 5, 7 -Tetrabromofluorescein. See Solvent red 43 2,2, 6,6 -Tetrabromo-4,4 -isopropylidenediphenol. See Tetrabromobisphenol A Tetrabromomethane. See Carbon tetrabromide Tetrabromophenol blue Tetrabromophenol sulfophthalein. See Bromophenol blue Tetrabromophthalate diol CAS 20566-35-2 EINECS/ELINCS 243-885-0 Empirical Ci5Hi6Br407 Properties Amber vise, liq. sol. in acetone, toluene insol. in water, alcohol m.w. 627.90 dens. 1.80 kg/l... 

Early applications of iron cationic species resulted from the facile reaction of a, a -dibromo-(and tetrabromo) acetone with Fe2(CO)9 with formation of the cation (A). Such cationic complexes can be efficiently trapped by olefin with formation of five-membered ketones. The reaction with conjugated dienes affords a straightforward access to tropones. Furan is a particularly good acceptor of these cationic complexes whereas their addition to enamines constitutes a potentially useful pathway to prostaglandins (cyclopentenones being thus obtained). 

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