Biaryl amine ligands for lanthanide catalysed enantioselective hydroamination/cyclisation of aminoalkenes

Arylations of (R)-2,2'-diamino-6,6'-dimethylbiphenyl and the corresponding racemic compound under palladium catalysis gives a range of C-2-symmetric secondary amine proligands H2L. The 3,5-di-tert-butylphenyl substituted compound reacts with the silylamides [M{N(SiMe2H)(2)}(3)(THF)(2)] (M=Y, Sm, La) to produce (+/-)-[ML{N(SiMe2H)(2)}(THF)(2)]. However, deprotonation of more sterically hindered proligands H2L proceeded very slowly, but the reaction with the more basic akylamide [Y((NPr2)-Pr-i)(3)(THF)(2)] gave [YL1-4((NPr2)-Pr-i)(THF)(2)] readily. Such catalysts formed in situ from the amine proligand H2L and metal amide. cyclised 2,2'-dimethylaminopent-4-ene to the corresponding pyrrolidine with enantiomeric excesses up to 50%. The alkylamide catalysts gave significantly faster turnover than the sitylamides. (C) 2003 Elsevier Ltd. All rights reserved.