New Chiral Lanthanide Amide Ate Complexes for the Catalysed Synthesis of Scalemic Nitrogen‐Containing Heterocycles

Abstract

New chiral binaphthylamido yttrium and ytterbium ate complexes with lithium and potassium counterions have been synthesised and characterised. X-ray structures have been obtained for [Li(thf)4][Ln{(R)-C20H12(NC5H9)2}2] (Ln=Yb, Y) and [K(thf)5][Yb{(R)-C20H12(NCH2CMe3)2}2] as isostructural complexes. The efficiency of these complexes for the enantioselective intramolecular hydroamination was examined. [Li(thf)4][Yb{(R)-C20H12(NC5H9)2}2] afforded the highest enantiomeric excess (up to 87 %) for the synthesis of a spiropyrrolidine, while [Li(thf)4][Y{(R)-C20H12(NC5H9)2}2] proved to be slightly more active. The role of the counter cation in the active catalytic species was evidenced by the comparison between lithium and potassium ate complexes. The most active catalyst of this series, [Li(thf)4][Yb{(R)-C20H12(NCH2CMe3)2}2], was successfully used for the cyclisation of aminopentenes with internal double bonds.