Effects of solvent and base on the palladium-catalyzed amination: PdCl_2(Ph_3P)_2/Ph_3P-catalyzed selective arylation of primary anilines with aryl bromides

摘要

A readily accessible catalytic system, PdCl_2(Ph_3P)_2/Ph_3P, was developed for the selective arylation of primary anilines with aryl bromides. The strong influence of solvents and bases on the catalytic activity was observed. In refluxing o-xylene, triphenylphosphine shows high efficiency for Pd-catalyzed intermolecular amination reactions. By changing the bases, mono- and diarylation of primary amines could be selectively achieved in high yields. Moreover, the catalytic system showed good toleration for the steric hindrance of anilines. A series of N,N,N',N'-tetraaryl-1,1'-biphenyl-4,4'-diamines, important intermediates of OLED hole transport materials, were synthesized facilely via coupling reactions between 4,4'-diaminobiphenyls and aryl bromides.