Catalytic asymmetric aza Diels-Alder reactions of hydrazones using a chiral zirconium catalyst

Catalytic asymmetric aza Diels-Alder reactions of acylhydrazones with Danishefsky’s dienes have been developed. A chiral zirconium complex derived from zirconium propoxide and 3,3′,6,6′-I₄BINOL was found to be effective in this reaction, and the desired optically active 2,3-dihydro-4-pyridone derivatives were obtained with high enantioselectivities. Asymmetric formal synthesis of a natural product, coniine, was conducted using this catalytic asymmetric reaction as a key step.