Anion Rearrangements of Alkali Metal Complexes of the Chiral Amine (S)-N-α-(Methylbenzyl)phenylallylamine: Structural and Solution Insights

Reaction of the chiral amine ( S )- N -α-(methylbenzyl)phenylallylamine, [( S ) -N -α-mbpa], with n BuM (M = Li, Na, K) in the presence of the Lewis donors TMEDA or THF (TMEDA = N, N, N ′, N ′-tetramethylethylenediamine, THF = tetrahydrofuran) resulted in a series of mono- or dimetalated complexes, [{PhC(H)CH 3 NC(H)C(H)C(H)PhLi 2 (TMEDA) 2 ] 1, [{PhC(H)CH 3 NCH═CHCH 2 PhNa(TMEDA)] 2 2, and [PhC(═CH 2 )N(CH 2 CH 2 CH 3 )K] ∞ 3, being formed with various 1,3-sigmatropic rearranged allylic bonding patterns. Completing previous work on the related amine N -α-(methylbenzyl)allylamine, the potassiated aza-enolate complex [( R )-{(PhC(═CH 2 )N(CH 2 CH 2 CH 3 (THF)] ∞ 4 is also reported. All four complexes 1 – 4 have been characterized by single-crystal X-ray diffraction and solution NMR spectroscopy studies. DTF calculations on model systems investigated the preference for the monomeric Li 2 -mbpa 1 to undergo isomerization to the aza-allyl anion conformation, which, interestingly, is more energetically stable as a monomeric complex.