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Bridging Bromide, oxidation

Hydroxyl Compounds. The aqueous chemistry of zirconium is complex, and in the past its understanding was compHcated by differing interpretations. In a study of zirconium oxide chloride and zirconium oxide bromide, the polymeric cation [Zr4(OH)g (H20)jg was identified (189) the earlier postulated moiety [Zr=0] was discarded. In the tetramer, the zirconium atoms are coimected by double hydroxyl bridges (shown without the coordinating water molecules) ... [Pg.436]

The thermodynamic stabilities of phenonium ions have been determined based on bromide-transfer equilibria in the gas phase and, depending on the substituents, the bridged species (1) has been proposed as an intermediate or transition state on the potential-energy surface for the 1,2-aryl rearrangement of triarylvinyl cations (see Scheme 1). Phenonium ion (3) has been presented as an intermediate to account for the fact that lactonization of methyl 4-aryl-5-tosyloxy hexanoate (2) produces y-lactone (4) selectively under thermodynamic conditions, but affords 5-lactone (5) preferentially under kinetic conditions. It has been shown that anodic oxidation of frany-stilbene in alcohols in the presence of KF or BU4NBF4 is accompanied by its electro-oxidative rearrangement into diphenylacetaldehyde acetals. The mechanism outlined in Scheme 2 has been proposed" for the transformation. [Pg.487]

The allylic alcohol 176, prepared by the hydrolysis of allylic bromide 173 <2004JME1423>, was oxidized with MnOz to the corresponding aldehyde 177, which reacted easily with allyl bromide in the presence of zinc under Barbier s conditions to give the adduct 178 (Scheme 25). Of particular note is the fact that the peroxide bridge was not sensitive to Zn under these reaction conditions <20050L5219>. [Pg.877]


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See also in sourсe #XX -- [ Pg.124 ]




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