The chiral diether ligand controlled asymmetric conjugate addition of organolithiums
to nona-2,7-dienedioates preferentially proceeds via the s-cis conformation with coordination of the carbonyl oxygen atom to the lithium to give
a lithium E-enolate intermediate. Subsequent intramolecular conjugate addition of the enolate
also proceeds via a cyclic transition state involving the lithium and the s-cis-enoate, resulting in trans,trans-trisubstituted cyclohexanes with high enantiomeric excesses and yields.
Key words
chiral ligand - asymmetric synthesis - organolithiums - conjugate addition - cascade
reaction