Enantioselective Alkynylation of Aldehydes by Mixed Aggregates of 3‑Aminopyrrolidine Lithium Amides and Lithium Acetylides

Lithium acetylides form, with 3-aminopyrrolidine
lithium amides,
noncovalent 1/1 mixed aggregates that have been characterized by 1D
and 2D multinuclear NMR spectroscopy and DFT computations. The results
show that the complex adopts a structure organized around a N–Li–C–Li
core and that the acetylide appendage lies within the plane of this
quadrilateral, midway between the two lithium cations. These complexes
have been employed for the enantioselective alkynylation of a series
of aromatic aldehydes and provided the expected propargylic alcohols
in ee values up to 85% in THF at −78 °C.