DABCO-catalyzed regioselective cyclization reactions of β,γ-unsaturated α-ketophosphonates or β,γ-unsaturated α-ketoesters with allenic esters.

Highly efficient DABCO-catalyzed [4 + 2] cycloaddition of β,γ-unsaturated α-ketophosphonates or β,γ-unsaturated α-ketoesters with allenic esters gives the corresponding highly functionalized tetrahydropyran and dihydropyran derivatives in good to excellent yields and moderate to good regioselectivities under mild conditions.