Preparation of enantiopure biimidazoline ligands and their use in asymmetric catalysis
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Updated: Aug 23, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Nicola A Boland1, Mike Casey, Stephen J Hynes
1Chemistry Department, the Centre for Synthesis and Chemical Biology, the Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland.
Abstract:
A convenient new method for the preparation of 2,2'-biimidazolines is reported. Amino alcohols were reacted with dimethyl oxalate, and the product hydroxy amides converted into chloroamides by reaction with thionyl chloride. Treatment with PCl5, followed by diamines (ethanediamine, propane-1,3-diamine, 2,2-dimethylpropane-1,3-diamine) furnished a series of enantiopure tricyclic biimidazolines. Complexes of two of the ligands with PdCl2 were prepared and their X-ray crystal structures were determined. The biimidazolines were tested as ligands for asymmetric Pd-catalysed allylations. Moderate enantioselectivity (up to 80% ee) was found for the reaction of dimethyl malonate with diphenylallyl acetate, with the 5,7,5 fused tricyclic systems outperforming the 5,6,5 analogues. The corresponding reaction of pentenyl acetate gave lower enantioselectivity (44-57% ee), and proved very sensitive to the donor strength of the ligands, the stronger donors giving lower yields. The results provide a further demonstration of the value of the 'tunability' of imidazoline ligands.
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