89057-44-3

At about -78 °C, 2.04 g (10 mmol) of 5,10-tetrahydrodianaphthene (Intermediate I-3) and 37.5 mL (60 mmol) of n-butyllithium (1.60 M hexane solution) were gradually reacted in tetrahydrofuran. Subsequently, 3.8 mL (60 mmol) of iodomethane was added and the reaction mixture was stirred at room temperature for about 3 hours. Upon completion of the reaction, 5 mL of aqueous 1N hydrochloric acid was added to the mixture to quench the reaction. The organic phase was separated and the aqueous phase was extracted with dichloromethane (2 x 100 mL). The organic phases were combined and dried over magnesium sulfate, followed by evaporation of the solvent. The residue was separated and purified by silica gel column chromatography to afford 2.03 g of 5,10-tetramethyldiindene (Intermediate I-4) in 78% yield. The compound was characterized by mass spectrometry/fast atom bombardment mass spectrometry (MS/FAB). The calculated molecular weight of the molecular formula C20H20 was 260.37 and the measured value was 260.45.

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