An NHC-catalyzed, stereoselective α-functionalization of α,β-unsaturated carboxylic acids through in situ activation.

An N-heterocyclic carbene (NHC)-catalyzed α-functionalization of the in situ activated α,β-unsaturated carboxylic acids bearing γ-H was realized through formal [4 + 2] annulations with o-quinone methides, which paved a new avenue for the assembly and modification of the dihydrocoumarin scaffold in good yields with excellent diastereo- and enantioselectivities.