Study of the Schiff Base to Enamine-Ketone Rearrangement upon Condensation of Formyl Functionalized 2-Oxaindane Series Spiropyran with Aliphatic Amines

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This work focuses on the formyl derivative of 2-oxaindane series spiropyran under its condensation reaction. The data indicated that all products are thermodynamically stable enamine-ketone tautomeric form in both DMSO solution and solid state. This finding can be explained by the migration of proton in 7-hydroxy group to the azomethine nitrogen, which is conjugated with electrocyclic opening of the spirounit in the non-stable Schiff-bases. We observe the enamine-ketones dynamic equilibrium of Z-, E-isomers in the DMSO solution. X-Ray diffraction study was performed for single crystalline sample of aminoethanol derivative. The synthesized compounds were evaluated in vitro cytotoxic activity against four typical human cell lines, showing moderate activity against lung carcinoma (LU-1), hepatocellular carcinoma (Hep-G2), breast carcinoma (MCF-7), and undifferentiated thyroid carcinomas (8505c). Among them, the compound with R = i-Pr showed the best activity with IC50 values 10.60 (MCF-7), and 10.55 µM (8505c). The in vitro antioxidant activity test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) showed that all the synthesized compounds have weak or no activity.