Stereoselective and regioselective condensation reactions of coordinated aminoacetone

Abstract

Treatment of cis-[Co(en)₂(NH₂CH₂R)(NH₂CH₂COCH₃)]³⁺ ions (R = H, Me, CH₂Br, Ph, p-C₆H₄Cl) with base leads to imine complexes where the coordinated aminoacetone has reacted with a bound monoamine RNH₂ or an ethylenediamine moiety. The product distribution appears to be determined by the relative acidity of the monoamine and the ethylenediamine amine centres; condensation is preferred at the most acidic site. Reduction of the imine group in these complexes with BH₄^- ion leads to new complexes of the type [Co(en)2(NH₂CH₂CH(Me)NHCH₂R)]³⁺ and [Co(en)(NH₂CH₂CH₂NHCH(Me)CH₂NH₂)(NH₂CH₂R)]³⁺ in which the reduced ligand is synthesized stereospecifically.