The inverse-electron demand Diels–Alder reaction of tetrazines with cyclic enol ethers

Inverse electron-demand Diels–Alder additions (iEDDA) between 1,2,4,5-tetrazines and suitable unsaturated dienophiles such as olefins, alkynes, or enol ethers provide facile access to pyridazines. Herein the use of cyclic enol ether derivatives for preparing pyridazines bearing 2-hydroxyethyl, 3-hyproxypropyl, and 3-oxopropyl substituents at the 4-position is disclosed and second order rate constants for the reactions with 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, and 2-methoxy-3,4-dihydro-2H-pyran are presented.