Asymmetric Henry Reaction Catalyzed by Diamine-Copper(II) Complex

Significance

In 1992, Sihibasaki and co-workers reported the first example of an enantioselective Henry reaction using a BINOL-based heterobi-metallic system (J. Am. Chem. Soc. 1992, 114, 4418). In the years since, this field has received much attention and various organocatalytic and metal-based catalyst systems have been developed. In the present paper, the authors report the use of a known proline-derived C ₂-symmetric ligand L1 and Cu(OAc)˙H₂O as an effective catalyst system for this reaction. A wide range of functionalized aromatic aldehydes as well as aliphatic aldehydes are tolerated to afford nitroaldol products in high yields and enantiomeric ratios. Several examples of diastereoselective Henry reactions are shown, however, the diastereomeric ratios are rather low.