Proline-catalyzed direct inverse electron demand Diels-Alder reactions of ketones with 1,2,4,5-tetrazines

An organocatalytic direct inverse electron demand Diels-Alder reaction of ketones with 1,2,4,5-tetrazines has been developed. The process is efficiently catalyzed by proline to give Diels-Alder adducts pyridazines in high yields.