Dual‐action catalyst: A Brønsted acid catalyzed regioselectivecycloisomerization was found to be highly effective for the preparation of structurally diverse 2,3‐dihydro‐4H‐pyran‐4‐ones in a 6‐exo‐trig manner from the corresponding 5,2‐enyne‐1‐ones. In this reaction, the Brønsted acid acts as a dual catalyst activating both the carbonyl and alkene moieties in a cascade manner (see scheme).