Water carbonyl dibromide

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,... 

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. " In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in... 

Nair et al. (2001) describe the bromination of alkenes using a mixture of ammonium hexanitratocerate(IV) and potassium bromide in a two-phase system consisting of water and dichloromethane. For instance, styrene is transformed by this reaction system in excellent yield at room temperature into 1,2-dibromo-phenyl ethane (scheme 28). It is assumed that the bromide ion is first oxidized by CAN to the bromine radical, which subsequently undergoes addition to the double bond to produce a benzylic radical. Trapping of another bromine radical results in the formation of the 1,2-dibromide. The method is not only applicable to substituted styrenes, but also to alkenes and o, 5-unsubstituted carbonyl compounds. However, the choice of the solvent is of prime importance the reaction only occurs in the water/dichloromethane two-phase system. In other solvents, like aqueous solutions of methanol or acetonitrile, a variety of products such as phenacyl bromides and nitratobromides are formed (scheme 29). The nitrato bromides are formed exclusively when the reaction is carried out in a deoxygenated atmosphere. In the two-phase system water/dichloromethane, side reactions are avoided be-... 

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