Asymmetric Diels- Alder Reactions of 2,4,6-Trienals via Tetraenamine Catalysis

While significant progress has been made in Diels-Alder cycloadditions of 2,4-dienals by the formation of trienamine intermediates, we report that the further extended tetraenamine species can be generated from 2,4,6-trienal substrates, which subsequently act as 3,6-regioselective diene partners in asymmetric Diels-Alder reaction with 3-olefinic oxindole dienophiles. An array of highly functionalized spirocyclic compounds were produced in good stereoselectivity up to 96% ee and greater than 19:1 d.r., and with fair to moderate yields of 40-67%.