Asymmetric Henry Reaction of 2-Acylpyridine N-Oxides Catalyzed by a Ni-Aminophenol Sulfonamide Complex: An Unexpected Mononuclear Catalyst

Abstract

The asymmetric Henry reaction of 2-acylpyridine N-oxide remains a challenge as N-oxides generally act as competitive catalyst inhibitors or displace activating ligands. A novel variable yield (up to 99%) asymmetric Henry reaction of 2-acypyridine N-oxides catalyzed by a Ni-aminophenol sulfonamide complex with good to excellent enantioselectivity (up to 99%) has been developed. Mechanistic studies suggest that the unique properties of the electron-pairs of N-oxides for complexation with Ni makes the unexpected mononuclear complex, rather than the previously reported dinuclear complex, the active species.

Triton B Catalyzed Rapid and Mild Synthetic Protocol for both Henry Reaction of Isatin and Michael Reaction of Chalcone with Nitroalkane

“…7 Furthermore, the Henry reaction has been used in the synthesis of -nitroethanols 8 and for Ni-aminophenol sulfonamide complex catalyzed synthesis of optically active pyridine-containing -nitro tert-alcohols. 9 Similarly, Michael adducts 1,3-diaryl-4-nitro-1-butanones are versatile structures with promising biological activities such as anticancer, antiplant-viral, antimicrobial, and anti-HIV properties. 10 The absolute configuration determines the biological activities of the scaffold.…”

Special Issue: Development of Asymmetric Synthesis

“…Thus, the article by Claros et al shows the use of a family of enantiopure ruthenium complexes bearing phosphonite of phosphinite ligands in the catalytic asymmetric transfer hydrogenation of aryl ketones with isopropyl alcohol as a hydrogen source, obtaining in some cases high conversions and enantioselectivities of the corresponding benzyl alcohols [3]. Another example of the use of chiral metal complexes as catalysts in asymmetric synthesis is shown by Liu et al [4]. In this case, a chiral nickel-aminophenol sulfonamide complex is employed as a catalyst for the asymmetric Henry reaction between 2-acylpyridine N-oxide-including ketones with nitromethane; the reaction is a challenge as N-oxides generally act as competitive catalyst inhibitors or displace the ligands.…”