One‐Pot Enantioselective Synthesis of 3‐Nitro‐2H‐chromenes Catalyzed by a Simple 4‐Hydroxyprolinamide with 4‐Nitrophenol as Cocatalyst

Abstract

AbstractThe asymmetric domino oxa‐Michael–Henry reaction of salicylaldehyde derivatives with trans‐β‐nitro olefins catalyzed by a readily available trans‐4‐hydroxy‐L‐prolinamide with 4‐nitrophenol as an effective cocatalyst is presented. The corresponding 3‐nitro‐2H‐chromenes were obtained in moderate to excellent yields (up to 99 %) and with up to 90 % ee under mild conditions. In addition, a preliminary study shows that this organocatalytic system is able to promote the domino aza‐Michael–Henry reaction of 2‐formylpyrrole derivatives with trans‐β‐nitro olefins to give chiral 2‐nitro‐3H‐pyrrolizines.