Direct construction of 3′,4′-dihydrospiro[pyrrol-3,2′-oxindoles] through a cascade Michael/cyclization reaction of 3-aminoindolin-2-ones with enones/enals

A simple and efficient cascade Michael/cyclization reaction of 3-aminoindolin-2-ones with enones/enals was identified for the synthesis of potentially biologically active 3′,4′-dihydrospiro[pyrrol-3,2′-oxindoles], using DBU as an efficient catalyst and ethylene glycol as an environmentally benign solvent. More diverse 3′,4′-dihydrospiro[pyrrol-3,2′-oxindoles] analog libraries were prepared in good yields (up to 97%). The structure of 3′,4′-dihydrospiro[pyrrol-3,2′-oxindoles] was confirmed by mass spectrometry analysis, NMR analysis and single crystal X-ray diffraction. The main advantages of this method include the availability of starting materials, simple experimental operation, short reaction time, as well as high yields observed.

Graphical abstractA simple and efficient cascade Michael/cyclization reaction of 3-aminoindolin-2-ones with enones/enals was identified for the synthesis of potentially biologically active 3′,4′-dihydrospiro[pyrrol-3,2′-oxindoles], using DBU as an efficient catalyst and ethylene glycol as an environmentally benign solvent. The main advantages of this method include the availability of starting materials, simple experimental operation, short reaction time, as well as high yields observed.Figure optionsDownload full-size imageDownload as PowerPoint slide