Carbonyl dibromide bromide

Treatment of pyridinium benzoate with carbonyl dibromide in toluene gives benzoyl bromide [1919] ... 

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture.74 In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in 1.5 h, while the same reaction gave only less than 50% yield in a variety of other organic solvents such as ether, benzene, or ethyl acetate, even after a reaction time of 10 h. The reaction was equally successful with a combination of allyl bromide, tin metal, and a catalytic amount of hydrobromic acid. In the latter case, the addition of metallic aluminum powder or foil to the reaction mixture dramatically improved the yield of the product. The use of allyl chloride for such a reaction,... 

The nature of the organotin intermediates has been studied. It was found that when allyl bromide and tin reacted in aqueous media, allyltin(II) bromide was first formed and then was followed by the formation of diallyltin(IV) dibromide (See also Section 6.4.1, Eq. 6.12b). Either of the two organotin intermediates can react with carbonyl compounds to give the corresponding homoallylic alcohols. However, the tin(II) species was found to be more reactive than the tin(IV) species (Eq. 8.38).81... 

MeOH/AcOH-(Allyl)2SnBr2-(Pt) system at 50 55 °C. As illustrated in Scheme 149 [530], diallyltin dibromide (428) produced from metalKc Sn and allyl bromide in methanol reacts with carbonyl compounds (426) to give the allylated products (427) together with allyldibromotin monomethox-ide (430). The latter compound (430) may be reduced at the cathode to di- or zero-valent Sn, which reacts smoothly with allyl bromide to regenerate diallyltin di-bromide (428). 

Alkenes, alkynes, and arenes, e.g., ethylene, acetylene and benzene, respectively, react (1) with bromine by addition, e.g., ethylene dibromide C HiBri (1.2). acetylene tetrabromide C2H .Br4 1,1,2,2. hexabromocyclo-hexane QHgBr also carbon monoxide yields carbonyl bromide COBr2i (2) with hypobromous add by addition. e.g., olefins form, for example,... 

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