Peroxometal-mediated environmentally favorable route to brominating agentsand protocols for bromination of organics

Higher-valent transition metals react with H2O2 to form peroxometallates, t hereby activating the coordinated peroxide. Based on the reaction profiles of peroxometal species, environmentally acceptable newer syntheses of tetra butylammonium tribromide (TBATB): Bu4NBr3, cetyltrimethylammonium tribromid e (CTMATB), cetyl(Me)(3)NBr3, and tetraethylammonium tribromide (TEATB), Et 4NBr3, have been developed from the reactions of the corresponding quaterna ry ammonium bromides with H2O2 and a catalytic amount of vanadium(V) or mol ybdenum(VI). Other transition metals capable of activating peroxide give si milar results. The quaternary ammonium tribromides (QATBs) thus produced, e specially TBATB and CTMATB, very efficiently act as clean and selective bro minating agents for a variety of organic substrates. Very facile brominatio n of organic substrates, including aromatics? is also possible by tetrabuty lammonium bromide (TBAB) Bu4NBr, either promoted by V2O5-H2O2 Or. catalyzed by MoO42--H2O2. The scope of the protocols has been under scored, and the relevance to green chemistry has been highlighted.