Enantioselective Vinylogous Michael–Michael Cascade Reactions of 3‑Alkylidene Oxindoles and Nitroolefin Enoates

A novel bifunctional squaramide catalyzed vinylogous Michael–Michael cascade reaction of 3-alkylidene oxindoles with nitroolefin enoates was developed. This convenient, one-pot cascade reaction serves as a powerful tool for the enantioselective construction of potential bioactive chiral chromans, which have three continuous tertiary stereocenters, in moderate to good yields (up to 85%) with excellent stereoselectivities (up to >19:1 dr and >99% ee)

Enantioselective Organocatalyzed Vinylogous Michael Reactions of 3‑Alkylidene Oxindoles with Enals

An efficient asymmetric vinylogous Michael addition of 3-alkylidene oxindoles and enals has been achieved using a chiral TBS-protected diphenylprolinol catalyst. The γ-substituted alkylidene oxindoles obtained bear a chiral tertiary center and are afforded in moderate to good yields and good to excellent enantioselectivities