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In this study, the synthesis and characterization of novel indanone-based spiro-dihydrobenzofuran derivatives were examined. Firstly, chalcone-like compounds 4a-k, ($E)$-2-benzylidene-2,3-dihydro-1$H$-inden-1-one derivatives, were synthesized by the base-catalyzed addition of benzaldehyde derivatives to 2,3-dihydro-1$H$-inden-1-one. Then Mn(OAc)$_{3}$-mediated addition of dimedone (2) to the chalcone-like compounds gave two novel spiro-dihydrobenzofuran isomers: (3$S)$-6,6-dimethyl-3-aryl-6,7-dihydro-3$H$-spiro [benzofuran-2,2'-indene]-1',4(3'$H$,5$H)$-dione (5a-k) and (2'$S)$-6,6-dimethyl-2-aryl-6,7-dihydro-2$H$-spiro[benzofuran-3,2'-indene]-1',4(3'$H$,5$H)$-dione (6a-k) in good yields. The isomers were separated by column chromatography and their structures were elucidated on the basis of spectral data (NMR, IR) and elemental analysis.

In this paper, a fast, cheap, simple, sensitive and selective spectrophotometric method based on high spin peroxo-Fe(III)-EDTA complex in the alkaline medium was developed for the determination of hydrogen peroxide (H2 O2) in real water samples. The purple-coloured complex with a maximum absorbance at a wavelength of 525 nm was formed. Various parameters such as type of stabilizer reagent and its concentration, reaction time, Fe(III), EDTA and NH3 concentration were optimized. The method was confirmed with the Beer’s law with a molar absorption coefficient of 267.36 L mol? 1 cm? 1 in the 8.3 ×10? 6 –4.08 ×10? 3 mol/L concentration range. Sandell’s sensitivity of the proposed method was also calculated as 0.188 µg/cm2 . LOD and LOQ were determined as 2.5 ×10? 6 and 8.3 ×10? 6 mol/L, respectively. Intraday and interday relative standard deviation of the proposed method for 2.0 ×10? 4 mol / L of H2 O2 were found as 1.5% and 6.1%, respectively. The developed method is suitable for fast monitoring of H2 O2 in different types of aqueous water samples without any sample preparation steps and acceptable recovery values between 90% and 118% were obtained. In the sample analysis, H2 O2 removed solutions from the real water samples were used for blank correction in their analysis and this process provides more reliable and accurate results in real sample analysis. © TÜBİTAK, Authors thank Prof. Dr. Hüseyin Tural for his valuable contributions. Authors would like to thank Ege University Research Foundation Project No: 2015 Fen 062 for financial support.