Privileged structures: synthesis and structural investigations on tricyclic sulfonamides

Customized synthetic procedures for the obtainment of highly functionalizable free sulfonamide tricyclic structures having NH, O, S and SO₂ (Z group) in the central seven-membered ring are presented. Due to the role that tricycles and the sulfonamide group play in medicinal chemistry, attention have been also paid to the 3D arrangement of these molecules. Their molecular structures and conformational properties have been studied by single-crystal X-ray diffraction and quantum chemical methods (HF-SCF/6-311+G(d,p). The minimum energy geometries in the solid state (I, Z = O; II, Z = NH and III, Z = S, SO₂) have been compared with the minimum-energy geometries in the gas phase (invariably the type III geometry) and discussed with respect to the literature reference values. An effort was made to correlate the conformational differences observed in the solid-state and gas-phase with the nature of the Z grouping.