Zinc complexes formed by 2,2′-bipyridine and 1,10-phenanthroline moieties combined with 2-azanorbornane: modular chiral catalysts for aldol reactions

Elżbieta Wojaczyńska,Robert Wieczorek,Jacek Skarżewski,Jacek Wojaczyński,Łukasz Sidorowicz

doi:10.1039/c6nj02251k

Elżbieta Wojaczyńska, Robert Wieczorek + Show 3 more

Open Access

https://doi.org/10.1039/c6nj02251k

Copy DOI

Abstract

Zinc complexes of new hybrid chiral imine ligands based on a bicyclic skeleton appear to be effective modular catalysts in asymmetric aldol reactions.

Highlights

A quest for new, effective tools for asymmetric synthesis led to the concept of modular chiral ligands and catalysts – assemblies of individual fragments performing diverse and complementary roles.[1]
We decided to prepare a series of new hybrid catalysts using the reaction of aldehyde derivatives of phenanthroline, bipyridyl and pyridine with enantiopure primary amines based on the bicyclic skeletons
All four amines 3–6 were reacted with 1,10-phenanthroline-2-carboxaldehyde to give isomeric imines: two 2-azanorbornyl derivatives and and two compounds based on the bridged azepane skeleton and (Scheme 3)

Summary

Introduction

A quest for new, effective tools for asymmetric synthesis led to the concept of modular chiral ligands and catalysts – assemblies of individual fragments performing diverse and complementary roles.[1]. Two five-membered chelate rings are formed, in analogy to the known complexes of phenanthroline ligands bearing the appropriately located imine, oxime or pyridine fragment.[20] The coordination sphere of zinc(II) is presumably filled by acetate(s), a separate 1H NMR methyl signal of the coordinated anion(s) could not be observed due to the exchange with the free CH3COOÀ even at 200 K.

Results

Conclusion