Optisch aktive aromatische Spirane, 19. Mitt. Ermittlung von optimalen λ-Werten bei tri- bis polysubstituierten 2,2′-Spirobiindanen

Nearly all ligand parameters λ which were empirically determined from disubstituted 2,2′-spirobiindanes proved to be inaccurate for the calculation of the optical rotations of the title compounds by means of the so-called “shortened approach”, especially in the case ofo-alkylsubstituted carbonyl derivates. The modified parameters λ were now determined either by comparison of a series of similar substituted spirocompounds or — for the carbonyl derivates — from the torsional angles calculated from their13C NMR data.