Science of Synthesis

Liu, L.; Wang, D.; Li, C. -J., Science of Synthesis: Stereoselective Synthesis, (2011) 2, 614.

An iron(II) complex with the hindered bis[(hydroxyethyl)dihydrooxazole]pyridine (he-pybox) derived ligand ‌102‌ 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 (e.g., ‌103‌) with a range of aldehydes in good yields with excellent syn diastereoselectivity and up to 92% enantiomeric excess for the condensation products (e.g., ‌104‌) (‌Scheme 43‌).[‌71‌] The combination of the same ligand with zinc(II) salts also generates a remarkably efficient and water-compatible chiral Lewis acid.

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References