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 degrees C.
Heterocyclic Lithium Amides as Chiral Ligands for an Enantioselective Hydroxyalkylation with <i>n</i>-BuLi
作者:Nicolas Duguet、Sylvain M. Petit、Philippe Marchand、Anne Harrison-Marchand、Jacques Maddaluno
DOI:10.1021/jo8005396
日期:2008.7.1
Chiralheterocyclic structures based on 3-aminopyrrolidines (3APs), 3-aminotetrahydrothiophens (3ATTs), and 3-aminotetrahydrofurans (3ATFs) have been synthesized. The corresponding lithium amides have been evaluated as chiralligands in the condensation of n-BuLi on o-tolualdehyde. The returned levels of induction were in the 46−80% ee range. The cheap and easily prepared 3ATFLi’s turned out to be
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 degrees C.