Tandem Michael Addition–Ring Transformation Reactions of 3‑Hydroxyoxindoles/3-Aminooxindoles with Olefinic Azlactones: Direct Access to Structurally Diverse Spirocyclic Oxindoles

An
efficient method for the direct construction of two classes
of spirocyclic oxindoles by the reactions of 3-hydroxyoxindoles/3-aminooxindoles
and (Z)-olefinic azlactones through a tandem Michael
addition–ring transformation process has been developed. With
DBU as the catalyst, a range of spiro-butyrolactoneoxindoles and spiro-butyrolactamoxindoles,
containing an oxygen or a nitrogen heteroatom, respectively, in the
spiro stereocenter, were smoothly obtained with good to excellent
diastereoselectivities in high yields.