Michael addition / Nucleophilic acylation / Umpolung
Investigations aimed at elucidating the structure of lithiated and by cryoscopic measurements of (S,S)-6 in THF. Trapping experiments complement the results. In THF, which constitu-α-amino nitriles B have led to the identification of N-lithio αamino nitrile anions as characteristic structural features. tes the principal reaction medium, the lithiated amino nitriles B are found to exist as monomeric species B6 between Ϫ110 Their preparations, crystal structures, and solution structures under the reaction conditions, are described. X-ray crystal and +25°C. In less polar solvents, higher aggregation is presumed. NMR spectroscopic studies of 3 show that the favored structure analyses of crystalline 3 and (S,S)-4 reveal the presence of dimeric aggregates B4 with C i symmetry, held toge-orientations of the amine and phenyl groups are similar to their conformations in the solid state. In the light of the re-ther by four-membered NLiNLi rings, coordinatively saturated at lithium by four THF ligands. The crystal structure of sults obtained, a transition state is proposed to account for the relative topicity observed in the 1,4-additions of enantio-(S,S)-6 shows polymeric aggregation with dimeric subunits similar to those of 3 and (S,S)-4. The solution structure has pure lithiated α-amino nitriles (S,S)-4, (S,S)-5, and (S,S)-6 to Michael acceptors. been investigated by IR and Raman spectroscopy of 2, (S,S)-4 and (S,S)-6, by NMR spectroscopy of 3, (S,S)-5 and (S,S)-6,