Tandem Rh-Catalyzed [4 + 2] Vinylic C-H O-Annulation of Exocyclic Enones with Alkynes and 1,5-H Shift.

Active pyrylium intermediates are in situ generated by a Rh-catalyzed vinylic C-H annulation reaction between exocyclic α,ß-enones and alkynes, which undergo a base-promoted rearrangement via 1,5-H shift to form 1H-benzo[f]chromene derivatives.