The 4a′-Hydroxy-3′,3′,5,6′,6′,7-hexamethyl-3′,4′,4a′,6′,7′,9a′-hexahydrospiro[indole-3,9′-xanthene]-1′,2,8′(1H,2′H,5′H)-trione

Pseudo-multicomponent reactions (Pseudo-MCRs) have led to a variety of compounds with interesting biological properties, especially desirable in the pharmaceutical industry. The isatin nucleus could be considered a privileged scaffold for the design of biologically active substances. Dimedone is an interesting and versatile molecule for most organic transformations, especially one-pot and multicomponent reactions. Xanthene derivatives are still an attractive research field for both academia investigations and industry. In this investigation, a simple and efficient tandem Knoevenagel-Michael protocol with subsequent cyclization for the synthesis of the previously unknown 4a '-hydroxy-3 ',3 ',5,6 ',6 ',7-hexamethyl-3 ',4 ',4a ',6 ',7 ',9a '-hexahydrospiro[indole-3,9 '-xanthene]-1 ',2,8 '(1H,2 ' H,5 ' H)-trione was elaborated. The suggested method is based on the pseudo-MCR of 5,7-dimethylisatin and dimedone. The structure of the earlier unknown compound was proven using H-1, C-13-NMR, and IR spectroscopy, mass spectrometry, and elemental analysis. To compare the developed protocol with the existing ones, unsubstituted spiro[indole-3,9 '-xanthene] was synthesized. Its structure has been proven using two-dimensional (2D) NMR spectroscopy techniques.