Enantioselective Distal Functionalization of 3‑Cyano-4-methylcoumarins through Direct Vinylogous Conjugate Addition to Maleimides

An unprecedented organocatalyzed asymmetric vinylogous Michael reaction between 3-cyano-4-methylcoumarins and maleimides with an excellent enantiomeric ratio (up to 99.5:0.5) and yield (up to 95%) is reported. This remarkable selectivity is attributed to the hydrogen bonding ability of l--leucine-derived amine thiourea catalyst. The versatility, practical applicability, and scalability are demonstrated by the generation of γ-functionalized coumarin derivatives.