| Organolanthanide complexes of the general type Cp′ 2LnCH(TMS)2 (Cp′ = η5-Me 5C5; Ln = La, Sm, Y) and CGCSmN(TMS)2 (CGC = Me 2Si(η5-Me4C5)(tBuN)) serve as effective precatalysts for the rapid, regioselective, and highly diastereselective intramolecular hydroamination/cyclization of primary and secondary amines tethered to conjugated dienes. The rate enhancement with dienyl group as well as substituent group (R) effects on turnover frequencies is consistent with proposed transition state electronic demands. The rate law is first-order in [catalyst] and zero-order in [aminodiene], as observed in intramolecular hydroamination/cyclization of aminoalkenes, aminoalkynes, and aminoallenes. However, depending on the particular substrate and catalyst combination, deviations from zero-order kinetic behavior reflect competitive product inhibition or self-inhibition by substrate. Lanthanide ionic radius effects and ancillary ligation effects on turnover frequencies suggest a sterically more demanding Ln-N insertion step than in aminoalkene cyclohydroamination. A substantially more negative ΔS‡ implies a more highly organized transition state. Good to excellent diastereo-selectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de). Formation of 2-(prop-1-enyl)piperidine using the chiral organolanthanocene precatalyst proceeds with up to 71% ee.; C2-symmetric bis(oxazoline) lanthanide complexes of the type [(4R,5S)-Ph2Box]La[N(TMS) 2]2, (Box = 2,2′-bis(2-oxazoline)methylenyl) serve as precatalysts for the efficient enantioselective intramolecular hydroamination/cyclization of aminoalkenes and aminodienes. These new catalyst systems are conveniently generated in situ from the known metal precursors Ln[N(TMS)2] 3 or Ln[CH(TMS)2]3 and 1.2 equivalent of commercially available or readily prepared bis(oxazoline) ligands. The X-ray crystal structure of [(4S)-tBuBox]Lu[CH(TMS)2] 2 provides insight into the structure of the in situ generated precatalyst species. Aryl stereodirecting groups at the oxazoline ring 4 position and additional substitution (geminal dimethyl or aryl) at the 5 position are crucial for high turnover frequencies and good enantioselectivities. The optimized precatalyst, in situ generated (4R,5 S)-Ph2BoxLa[N(TMS)2]2, exhibits good rates and enantioselectivities, comparable to or greater than those achieved with chiral C1-symmetric organolanthanocene catalysts, even for poorly responsive substrates (up to 67% ee at 23°C. Hydroamination rates are zero-order in [amine substrate] and first-order in [catalyst], implicating that the same general mechanism as operative in previously characterized organolanthanide-catalyzed hydroamination/cyclizations, and the active catalytic species is monomeric. |
