An Efficient Carbene-Catalyzed Access to 3,4-Dihydrocoumarins

Dihydrocoumarins play an important role as flavor and fragrance compounds and can be prepared efficiently from o-hydroxycinnamaldehydes in a mild, atom-economic N-heterocyclic carbene-catalyzed redox lactonization. Corresponding coumarins are accessible via a one-pot domino oxidation lactonization procedure in the presence of oxidants.