Functionalized organolithium reagents in the synthesis of chiral ligands for catalytic enantioselective addition of diethylzinc to aldehydes

Series of functionalized organolithium compounds were prepared and added to chiral bicyclic ketones (1R-(+)-camphor analogue 2 and 1R-(−)-fenchone 3), resulting in the preparation of a small “library” of chiral aminoalcohols able to serve as ligands in metal mediated asymmetric synthesis. The configuration of the chiral ligands was approved by applying advanced NMR experiments. The absolute configurations of 1,2-disubstituted planar chiral ferrocene-based aminoalcohols 15, 18 and 19 were determined by means of NMR experiments and confirmed by X-ray crystallography. The new chiral ligands were tested as pre-catalysts for the addition of diethyl zinc to benzaldehyde. The reactions proceeded with excellent conversions and a moderate degree of enantioselectivity.

Graphical abstractSeries of functionalized compounds of type A and B have been synthesized and characterized. They are active ligands for the enantioselective addition of Et2Zn to benzaldehyde.Figure optionsDownload full-size imageDownload as PowerPoint slide