An Efficient Synthesis of Highly Functionalized [5,6] Aromatic Spiroketals by Hetero-Diels−Alder Reaction

A hetero-Diels−Alder reaction of vinyl sulfoxides with o-quinone methides precursor constructs highly functionalized [5,6] aromatic spiroketal skeletons in moderate to good yields with high regioselectivity. The two functional groups (ketone and olefin) can be further subjected to many synthetic transformations.