The strength of the weak: An L‐tert‐leucine‐derived amine–thioureacatalyst (see scheme, green box) promotes the asymmetric vinylogous conjugate addition reaction between γ‐aryl‐ and alkyl‐substituted butenolides with the butenamides and enoates shown. Computational studies show the preference for the observed stereochemistry is a result of favourable weak non‐bonding interactions, which stabilize
deconjugated butenolides with ortho‐quinonemethides generated in situ afforded a series of functionalized 3,4‐dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo‐ and enantioselectivity. DFT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic