Dynamic processes in organolithium chemistry: tetrameric and ‘open’ tetrameric chiral α-amino lithium alkoxides

Abstract

Lithium N,N,N′-trimethylethylenediamide, LiN(Me)(CH₂)₂NMe₂, 1-Li, reacts with 1 equiv. of benzaldehyde to afford the corresponding chiral α-amino lithium alkoxide 2, which in the solid state is a conventional pseudo-cubane tetramer. Reaction of 1-Li with o-methoxybenzaldehyde affords instead a novel ‘open’ pseudo-cubane tetramer 3, wherein the coordinative mode of the potentially bidentate N,N,N′-trimethylethylenediamino moiety can be related to ligand chirality. Employment of p-methoxybenzaldehyde results in the isolation of a tetramer 4, whose solid-state structure is intermediate between those of 2 and 3 and therefore suggests that fluxional processes may operate. Extensive studies of 2–4 in non-donor solution indicate diverse and complex behaviour.