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 %.