Efficient Synthesis of Functionalized 6‐(2‐Oxoindolin‐3‐yl)‐5‐azaspiro[2.4]heptanes

Abstract

The base catalyzed aldol condensation of various N‐benzylisatins with 1‐acetyl‐N‐arylcyclopropanecarboxamides resulted in functionalized 3‐hydroxyoxindolin‐2‐ones in high yields, which were in turn successfully transferred to functionalized 6‐(2‐oxoindolin‐3‐yl)‐5‐azaspiro[2.4]heptanes in acetic acid in the presence of the concentrated hydrochloric acid by sequential acid catalyzed dehydration and aza‐Michael addition process. The 1H NMR spectra and the single crystal structure indicated that the obtained functionalized 6‐(2‐oxoindolin‐3‐yl)‐5‐azaspiro[2.4]heptanes have a S,S‐configuration.