DETAILED STUDY DEFINING THE EXTENT OF PREORGANIZATION OF AN AZA MACROCYCLE CONTAINING THE PHENYLDINAPHTHOMETHANE SUBUNIT (A 3 BLADED PROPELLER) USING DYNAMIC NMR AND MOLECULAR-DYNAMICS

The aza-propeller crown 0-tritosyl-4,7,10-triaza-1,13-dioxacyclooctade cane 1 has been examined by variable temperature C-13 NMR studies, and the movement of each segment of the molecule (ArOCCN, NCCN, propeller ) was determined kinetically. Several sets of coalescences were found to occur at the same activation energy, which was also that found for the flip of the propeller segment. This movement of the macrocycle as a whole is a relatively slow process (ms scale) compared to the torsio nal movements round the crown ether ring (ps scale). These torsional m ovements were explored by molecular dynamics (MD) modelling; the macro cyclic ring is mobile when simulated at 200 K. The tosyl groups are in permanent motion although none twists by more than a few degrees roun d the N-S torsion. The segments next to the propeller (which are both gauche in the crystal structure) converted from gauche to :anti, while the TsNCCNTS segments remained anti throughout.