<i>N</i>‑Heterocyclic Carbene-Catalyzed [4 + 2] Cyclization of Saturated Carboxylic Acid with <i>o</i>‑Quinone Methides through in Situ Activation: Enantioselective Synthesis of Dihydrocoumarins

An <i>N</i>-heterocyclic carbene (NHC)-catalyzed formal [4 + 2] synthesis of dihydrocoumarins was realized from saturated carboxylic acids and <i>o</i>-quinone methides via an in situ activation strategy. This protocol results in excellent diastereoselectivity and enantioselectivity and good yields and uses readily available and inexpensive starting materials