Alkyl bromides transition-metal-catalyzed

Transition Metal-Catalyzed Coupling Reactions Synthesis of Aryl Amines. LHMDS was first used as a base to de-protonate alkylamines in the palladium-catalyzed synthesis of arylamines. This base is mild enough such that the alkyl-amide is generated at the transition metal center. Earlier examples reported that the reaction of an aryl bromide with cyclo-hexylamine and LHMDS in the presence of 5 mol % of (tri-o-tolylphosphine)2PdCl2 in toluene at 100 °C produced the desired arylamine in 89% yield after 2 h (eq 19). ... 

The penultimate unit effect may play a very important role in ATRR The rate constants of activation of monomeric and dimeric alkyl bromides with a CuBr-bpy (bpy=2,2 -bipyridine) complex as activator were determined. The ATRP relies on the reversible activation of a dormant alkyl halide through halogen abstraction by a transition metal complex to form a radical that participates in the classical free-radical polymerization figure (Fig. 2) prior to deactivation. In this equiUbrium, the alkyl radical (Pm ) is formed in an activated process, with a rate constant kact> by the homolytic cleavage of an alkyl halogen bond (Pm-Z) catalyzed by a transition metal complex in its lower oxidation state (Cu ). The relative values of fcact of the alkyl bromides were determined for CuBr/bpy catalyst systems in acetonitrile at 35°C. These systems followed the order EBriB (30) MBrP (3)>iBBrP (1) for monomeric initia-tors and MMA-MMA-Br (100) MA-MMA-Br (20) > MMA-MA-Br (5) > MA-MA-Br (1) for dimeric initiators. ... 

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