Tetraacyl hydrazines and 3,3′-biquinazoline-4,4′-diones; synthesis, studies of rotational barriers and deracemisation

The barrier to rotation around the N–N bond in 3,3′-biquinazoline-4,4′-dione is estimated to be 96 kJ mol−1, significantly higher than in acyclic tetraacyl hydrazines (84 kJ mol−1). Both dynamic chiroptical and NMR studies of 3,3′-biquinazoline-4,4′-diones which have an additional ring bridging the 2,2′ positions indicate that these compounds have a significantly higher barrier to rotation than the parent 3,3′-biquinazoline-4,4′-dione. Deracemisation of certain 3,3′-biquinazoline-4,4′-diones is possible via treatment with chiral acids at high temperature.