Abstract A new Lewis acid‐catalyzed endo ‐selective Prins bicyclization of γ,δ‐unsaturated aldehydes or ketones with a broad range of aldehydes to dioxabicyclo[2.2.2]octanes is disclosed. When using a chiral BINOL‐derived N ‐triflylphosphoramide (NTPA) as catalyst and glyoxylate esters as substrates, the cross‐dimerization afford functionalized bicyclic acetals with excellent diastereo‐ and enantioselectivities.