Organocatalytic Asymmetric (3+3) Cycloaddition of 4‐Hydroxycoumarins with α,β‐Unsaturated Aryl Esters

A chiral isothiourea‐catalyzed asymmetric (3+3) cycloaddition of 4‐hydroxycoumarins with β‐fluoroalkyl‐substituted α,β‐unsaturated aryl esters was established, which afforded chiral fluoroalkyl‐substituted caprolactone‐fused coumarins in moderate to good yields (up to 88%) and overall excellent enantioselectivities (up to 98% ee). This reaction not only enriches the chemistry of catalytic asymmetric (3+3) cycloadditions involving 4‐hydroxycoumarins, but also provides a new strategy for the synthesis of chiral six‐membered O‐heterocycle‐fused coumarins.