Interannular contraction upon oxidation of a mesoionic bicyclic imine
Abstract
The bicyclic imine (1) is oxidised exclusively at the thiadiazole ring to give the mono-,di-,and tri-oxides (2), (3), and (4); subtle but marked changes in the pattern of bonding and intramolecular interactions in the X-ray crystal structures of (1)–(4) reflect the increasing contribution of dipolar mesoionic forms [e.g.(1a)] along the series, and this in turn is reflected in the formation and chemistry of these oxides.