Diastereoselective CC Bond Formation with Nonracemic Planar‐Chiral η²‐Manganese Complexes

Abstract

Asymmetric alkylations and kinetically controlled aldol reactions are possible with the planar-chiral η2-manganese complexes of cyclopent-2-enone that can now be prepared in enantiomerically pure form [Eq. (a); LDA = lithium diisopropylamide; R = Me, allyl, Bn or RX = R′CHO, R′ = iPr, Ph]. After mild demetalation the chiral cyclopentenone derivatives, which are difficult to prepare by other means, are obtained with good enantiomeric excesses.