Synthesis And Optical Properties Of Nitrogen Bridgehead Heterocycles

This dissertation consists of the synthesis of 1,3,4-oxadiazole-containing pyrazolo[1,5-α]pyridine and pyrido[1,2-α]benzimidazole derivatives, and investigation on their photophysical properties.Azaindole-like nitrogen bridgehead compounds have attracted considerable attention from medicinal and organic research because of their similarities and diversities in structure to indole and purine which naturally exist within organism regulating genetic and metabolic process of life. The conjugatedπ-electron systems within these heteroaromatics can serve as both excellent bioisosteres for benzene-derived natural ligands and pharmacophoric appendages leading to an increase in binding affinity and subtype selectivity. Compounds containing nitrogen bridgehead heteroaromatic moieties have been reported to exhibit a variety of biological activities, such as calcium entry blockers, effective dopamine D3 and D4 receptor antagonists, adenosine A1 receptor antagonists and anti-inflammatory behavior. Besides of biological properties, nitrogen-containing compounds have also been widely used as fluorescent probes in the field of biological research and organic semiconductors in electroluminescent devices.We recently discovered a new efficient tandem reaction for the synthesis of nitrogen bridgehead compounds, including pyrazolo[1,5-α]pyridines, indolizines, imidazo[1,2-α]pyridines and pyrido[1,2-α]benzimidazoles. These heteroaromatics have been found to exhibit unique optical properties from our primary test. As far as we know, little attention has been paid on the photophysics of these nitrogen heteroaromatics, which are worthy of investigation.In this thesis, two series of 1,3,4-oxidazole-containing pyrazolo[1,5-α]pyridine and pyrido[1,2-α]benzimidazole derivatives were synthesized and their optical properties were investigated. Optical data reveal that these compounds exhibit blue or green emissions and have high quantum yields of fluorescence. These compounds have great potential for use as fluorescent pigments and optical/electrical materials.