Oxidants bromotrichloromethan

Hunsdiecker reaction Mercuric oxide. Bromotrichloromethane (solvent) (see Phosphorus pentabromide). 

Pecher et al. (2002) show how the uptake of ferrous iron from aqueous solution, by iron oxides, leads to the formation of a variety of reactive surface species that are capable of reducing polyhalogenated methanes (PHMs). The iron oxides used in the experiments and their characteristics are shown in Table 16.2. The PHMs studied include bromodichloromethane (CHBrCl ), chlorodibromomethane (CHBr Cl), bromoform (CHBr ), tetrachloromethane (CCl ), hexachloroethane (HCE), fluorotribromomethane (CFBrj), bromotrichloromethane (CBrCl ) and dibromodichloromethane (CBr Cy. 

Some variations of the method have been used to prepare cyclopropyl and cyclobutyl halides. Simultaneous addition of bromine and 3-bromocyclobutanecarboxylic acid to the suspension of mercuric oxide gives 1,3-dibromocyclobutane in good yield.7 Similarly, cyclopropanecarboxylic acid gives bromo-cyclopropane,9 and 3-(bromomethyl)cyclobutanecarboxylic acid gives 3-(bromomethyl)cyclobutyl bromide.10 In the latter reaction, it was found desirable to remove the water from the reaction as it is formed in order to obtain high yields. Another variation is the addition of a mixture of the acid and mercuric oxide to excess bromine in bromotrichloromethane.6... 

Poyer JL, Floyd RA, McCay PB, etal. 1978. Spin-trapping of the trichloromethyl radical produced during enzymic NADPH oxidation in the presence of carbon tetrachloride or bromotrichloromethane. Biochim Biophys Acta 539 402- 409. 

Eventually these reactions result in the oxidative destruction of cellular membrane and serious tissue damage in the liver even though <0.5% of CCI4 is ever metabolized. An essential involvement of lipid peroxidation in the events leading to death of hepatocytes has been proved in the acute intoxication as well as with other haloalkanes such as bromotrichloromethane (CBrCls), dibromoethane, and halothane. Lipid peroxidation is also involved in the hepatotoxicity of ethanol, allyl alcohol, and some drugs like adriamycin. 

When the Cristol procedure was applied to the bridgehead acid (1), bicyclo[2.2.2]octane-l-caiboxylic acid, with bromine and mercuric oxide in carbon tetrachloride, the product was a mixture of the expected bromide (2) with an even larger proportion of the unexpected chloride (3). The chloride evidently arises by abstraction of chlorine from the solvent by an intermediate bridgehead radical. The pure bromide was obtained with use as solvent of either bromotrichloromethane or 1,2-dibromoethane. 

The ring synthesis of the tetrahydro-1,3-azoles is simply the formation of N,N-, N,0-or A, S-analogues of aldehyde cyclic acetals the ring synthesis of the 4,5-dihydro-heterocycles requires an acid oxidation level in place of aldehyde. A good route to the aromatic systems is therefore the dehydrogenation of these reduced and partially reduced systems. Nickel peroxide, " manganese(IV) oxide, copper(II) bromide/ base, and bromotrichloromethane/diazabicycloundecane have been used. The example shown uses cysteine methyl ester with a chiral aldehyde to form the tetrahydrothiazole. 

The catalytic system consisting of PhIO and various iron porphyrins hydroxylates unactivated alkanes under ambient conditions [83,88]. The substrates studied were cyclohexane, cycloheptane, adamantane, cis-decahydronaphthalene and norcarane, and the catalysts - Fe(TPP)Cl, Fe(TTP)Cl, Fe(TNP)Cl and Fe(TMP)Cl. Monohydroxylated products predominated in all cases, with maximum yields of 30-39 % based on PhIO. High selectivity for tertiary centers (adamantane), retention of configuration at carbon (cis-decaline), and a large kinetic isotope effect (12.9) have ben observed. The free radical trap bromotrichloromethane changes the product distribution, pointing to a radical mechanism. The mechanism (Scheme 4) is essentially the same as that proposed previously for alkane oxidation by cytochrome P-450 [89]. 

Further study of the Fe -H202 reaction showed that bromotrichloromethane and its congeners afford bromination instead of o.vidation. The selectivity is the same as the oxidation reaction and does not follow a typical radical bromination pattern. [4] Scheme 2 shows a series of hydrocarbons and their relative reactivity normalized per hydrogen for radical bromination and for Gif type Fe -picolinic acid (PA)-H202 bromination. In each case, the C-H bond reactivity in cyclohe. ane is set at 1.0. The two sets of numbers are completely different. Cyclohe. ane is the most active hydrocarbon in Gif bromination and the least active in radical bromination. The data were... 

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