Metalation of the chiral amine (S)-N-R-(methylbenzyl)allylamine with n BuM (M ) Li, Na) leads to the formation of complexes with three distinct isomeric anion forms: allylamide [(PhC(H)CH 3 NCH 2 CHd CH 2 )] -, 1-aza-allyl [(PhC(H)CH 3 NC(H)CHCH 3 )] -, and aza-enolate [(PhC(dCH 2 )N(CH 2 CH 2 CH 3 )] -. The anionic form is dependent on the metal, the Lewis donor, and the thermal history of the complex. From their use in asymmetric syntheses and a previously described hmpa (hexamethylphosphoramide) complex, the allylamide form predominates with Li at room temperature in the presence of monodentate donors. The use of the bidentate donor tmeda (N,N,N′,N′-tetramethylethylenediamine) results in the crystallization and characterization of the 1-aza-allylic complex (S)-{[(PhC(H)CH 3 NC(H)CHCH 3 )Li} 2 • tmeda] ∞ , in which the allylamide moiety has undergone a 1,3-sigmatropic rearrangement. In the crystal structure, the tmeda molecules bridge rather than chelate the Li cations. The tridentate donor pmdta (N,N,N′,N′,N′′pentamethyldiethylenetriamine) gives crystals of [(PhC(dCH 2 )N(CH 2 CH 2 CH 3 )M • pmdta] (M ) Li, Na) in which a further rearrangement occurs to an aza-enolate form, resulting in a loss of chirality. Theoretical calculations on the various anion forms and the role of the metal and Lewis donors supported the solidstate observations, revealing a -75 kJ mol -1 energy gain on rearrangement of the anion from allylamide to either the aza-allylic or the aza-enolate form.

Reaction of the sodium anion of (S)-N-(alpha-methylbenzyl)allylamine with two equivalents of tert-butyl cinnamate results in a remarkable tandem aza-allyl conjugate addition-Michael addition-ring closure reaction, resulting in a chiral aminocyclohexane containing six new vicinal stereogenic centres with excellent levels of stereocontrol.