A Tunable and Enantioselective Hetero-Diels–Alder Reaction Provides Access to Distinct Piperidinoyl Spirooxindoles

Article abstract of DOI:10.1002/anie.201708355

The active complexes of chiral N,N′-dioxide ligands with dysprosium and magnesium salts catalyze the hetero-Diels–Alder reaction between 2-aza-3-silyloxy-butadienes and alkylidene oxindoles to selectively form 3,3′- and 3,4′-piperidinoyl spirooxindoles, respectively, in very high yields and with excellent enantioselectivities. The exo-selective asymmetric cycloaddition successfully regaled the construction of sp³-rich and highly substituted natural-product-based spirooxindoles supporting many chiral centers, including contiguous all-carbon quaternary centers.