Iron(II) and zinc(II) complexes with designed pybox ligand for asymmetric aqueous Mukaiyama-aldol reactions

An iron(II) complex with a hindered hydroxyethyl-pybox (he-pybox) ligand shows improved catalytic activity and enantioselectivity for asymmetric Mukaiyama-aldol reactions in aqueous media. This water-stable chiral Lewis acid promotes condensation of aromatic silyl enol ethers with a range of aldehydes with good yields, excellent syn-diastereoselectivity and up to 92% ee. The combination of the same ligand with ZnII salt is also demonstrated as a remarkably efficient and water-compatible chiral Lewis acid.