Fig. 3: NMR spectroscopy as an indicator for homoaromatic interactions.

Comparison of selected ¹H NMR chemical shifts of triasterane 14a, homoannulene ester 15 and annulene carboxylic acid 16 as an indication of homoaromatic interactions (400 MHz, CDCl₃, 298 K). Shown are a significant downfield shift of hydrogen atoms attached to the homoaromatic scaffold (labelled blue) and an upfield shift of the hydrogen atom placed within the ring current of the homoaromatic scaffold (labelled red). Also shown are a comparison to neutral compound 3, whose homoaromatic character has been refuted, and characterization data from the literature^28,31.