Photoinduced (4 + 2) Annulation of ortho -Hydroxyphenyl-Substituted para -Quinone Methides with Diazocarbonyls: Diastereodivergent Synthesis of 4-Aryl-dihydrocoumarins

Abstract A novel photoinduced (4 + 2) annulation of o-hydroxyphenyl-substituted p-quinone methides with diazocarbonyls, chemically initiated by a photochemical Wolff rearrangement, is described. Remarkably, the diastereoselectivity of this reaction can be switched by employing either TBAB/CaH2 or H2O as an additive, establishing an effective diastereodivergent approach to synthetically important functionalized 4-aryl-dihydrocoumarins.