Organolithium reagents chiral ligands

Reactions between organolithium reagents and 3-(2-naphthyl)-2H-azirine in the presence of a range of chiral ligands have been studied. The product aziridines are obtained in at best moderate ees [61]. 

As Stated earlier, the combination of an organolithium reagent with sparteine has been widely used to generate chiral carbanions. We will focus here on recent examples where the efficiency of sparteine was compared with other chiral chelating ligands. 

A major problem in the development of catalytic asymmetric 1,4-additions of RLi reagents is the high reactivity usually associated with organolithium species. One solution has been found in the stoichiometric formation of the corresponding chiral cuprates ee s of up to 99% have been reported [20]. An impressive example of the use of a substoichiometric quantity (33 mol%) of chiral ligand is to be found in... 

The C2 symmetric chiral diether 28" and the naturally occurring chiral diamine, (—)-sparteine (29), have been the most successful external chiral ligands for asymmetric conjugate addition of organolithium reagents. The rest of this review highlights organolithium addition, which is mediated or sometimes catalyzed by 28 or 29. 

SCHEME 2. Asymmetric conjugate addition of organolithium reagents with stoichiometric chiral ligands. Adapted with permission from Acc. Chem. Res., 40, 179-188 (2007). Copyright 2007 American Chemical Society... 

Reaction of Organolithium Reagents by Using External Chiral Ligands... 

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