Investigation of the C2-proton acidity of DiPh by 1H NMR spectroscopy Potassium hydride was washed five times with anhydrous toluene in a glove box containing pre-purified nitrogen to remove mineral oil. The cleaned KH was subsequently dried under vacuum. In the glove box, a vial was charged with KH (0.25 mmol) and DMSO-d6 (1.0 mL) was added. After H2 evolution had ceased, indene (0.5 mmol) was added, resulting in a green solution, indicative of indenyl anion formation. After reaction, the solution contained indene (0.25 mmol) and indenyl anion (0.25 mmol). A 1H NMR spectrum of this solution was recorded. Of the solution, 0.25 mL was taken and added to another vial. To this vial, 0.5 mL of DMSOFigure S4.19. 1H NMR spectra of indene and indenyl anion in a 1:1 ratio (top) and after reaction of this mixture with DiPh (bottom). The indenyl anion is sufficiently basic to deprotonate DiPh, as is evident from the disappearance of the indenyl anion signals in the bottom NMR spectrum.
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