Asymmetric Michael Addition of Ketones to Nitroolefins Catalyzed by a New Chiral Catalyst

Abstract

A new chiral catalyst was synthesized and found that it could catalyzed the asymmetric Michael reaction of ketones with nitroolefins smoothly at room temperature, giving the desired adducts in 71 -92% yields with excellent diastereoselectivities and high enantioselectivities (up to 95% ee). Unless otherwise noted, all reactions were carried out in solvent (1 mL) using 5a (0.14 mL, 5 equiv.) and 6a (0.25 mmol, 1 equiv.) in the present of 10 mol % 2 at rt. Determined by chiral HPLC analysis (chiralpak AS-H).

Hydrogen‐Bonding in Aminocatalysis: From Proline and Beyond

“…Attempts to introduce other (thio)urea‐related scaffolds with one‐atom linker between two hydrogen‐bonding units were also made resulting in the development of synthetic protocols leading to catalysts 41 b – f (Scheme ) 22. 23 Moieties that were successfully incorporated include: sulfonamide,22 aminobenzimidazole,23a 2‐nitroguanidine23b or 2‐aminopyridine23c groups. Interestingly, it is postulated that 2‐aminopyridyl moiety can upon protonation serve as a double‐hydrogen‐bond‐donating unit.…”