Easy Routes towards Chiral Lithium Binaphthylamido Catalysts for the Asymmetric Hydroamination of Amino-1,3-dienes and Aminoalkenes

The preparation of chiral lithium salts of N,N'-disubstituted binaphthyldiamines and their use as catalysts for asymmetric hydroamination/cyclisation of amino-1,3-dienes and aminoalkenes are reported. Several straightforward methods involving the combination of ligand with solutions of methyl- or [(trimethylsilyl) methyl] lithium (LiCH2TMS) by ex situ or in situ preparation have been investigated. The use of LiCH2TMS in an in situ procedure was revealed as the easiest for carrying out reactions with reliable results by fine-tuning the quantity of base. Screening of a variety of ligands led to the selection of binaphthyldiamines modified by benzyl, pyridyl or naphthyl groups for the cyclisation of conjugated aminodienes in pyrrolidine or piperidine with the highest stereo- and enantioselectivities described to date (up to 61 and 72% ee, respectively). Primary and secondary aminoalkenes are efficiently cyclised at room temperature, but with poor enantioselectivities.