RESUMEN
[reaction: see text] Peptide-based chiral ligands, readily prepared from commercially available materials, are used to promote Cu-catalyzed asymmetric allylic alkylations of alpha,beta-unsaturated esters bearing a gamma-phosphate with various alkylzinc reagents. These transformations lead to the formation of alpha,alpha'-dialkyl-beta,gamma-unsaturated esters in high yields as well as high regio- (re) and enantioselectivities (ee).
Asunto(s)
Compuestos Alílicos/química , Cobre/química , Hidrocarburos/síntesis química , Alquilación , Catálisis , Ésteres , EstereoisomerismoRESUMEN
Highest enantioselectivities so far with dialkylzinc reagents! Quaternary carbon centers are formed enantioselectively through a Cu-catalyzed allylic substitution reaction that is promoted by pyridinyl peptide-based ligands in the presence of dialkylzinc reagents. The modularity of this new class of chiral ligands is exploited for reactivity and selectivity optimization.
RESUMEN
A method for enantioselective Cu-catalyzed allylic substitution between various alkylzincs and alpha,beta-unsaturated carboxylic esters that bear a gamma-phosphate is reported. These transformations afford alpha-alkyl-beta,gamma-unsaturated carbonyls with regioselectivities of 7:1 to >20:1 (S(N)2':S(N)2) and in 87-97% ee. The utility of the method is illustrated by a convergent total synthesis of topoisomerse II inhibitor (R)-elenic acid.