N,N′-Dibenzosuberyl-1,1′-Binaphthyl-2,2′-diamine: A Highly Effective Supporting Ligand for the Enantioselective Cyclization of Aminoalkenes Catalyzed by Chelating Diamide Complexes of La(III) and Y(III)

Abstract

Enantioselective hydroamination/cyclization of representative aminoalkenes catalyzed by chelating diamide complexes of La(III) and Y(III) are described. It is noteworthy that the La(III) complex derived from the sterically demanding (<i>R</i>)-<i>N</i>,<i>N</i>′-dibenzosuberyl-1,1′-binaphthyl-2,2′-diamine proligand provides enantioselectivities that are in many cases significantly higher than those obtained with the corresponding Y(III) analogue. In addition, the presence of LiCl was typically found to suppress both the rates and the enantioselectivities obtained with the Y(III) complex when compared to its La(III) counterpart, in addition to completely suppressing the bicyclization of <b>7b</b>. The amide complexes employed in the latter study were prepared by ‘amine elimination’ using the new, highly active bases La[N(TMS)(<i>t</i>-Bu)]₃ and Y[N(TMS)(<i>t</i>-Bu)]₃.