Convergent synthesis, resolution, and chiroptical properties of dimethoxychromenoacridinium ions

Article abstract of DOI:10.1021/ol501692r

Cationic azaoxa[4]helicenes can be prepared in a single step from a common xanthenium precursor by addition of nucleophilic amines under monitored conditions (160°C, 2 min, MW). The (-)-(M) and (+)-(P) enantiomers can be separated by chiral stationary-phase chromatography. Determination of the absolute configuration and racemization barrier (ΔG ^a (433 K) 33.3 ± 1.3 kcal·mol ^-1) was achieved by VCD and ECD spectroscopy, respectively.