Pyrroloquinolines, imidazoquinolines, and pyrroloquinazolines with a bridgehead nitrogen

This chapter presents recent advances in the chemistry of heterocyclic ring systems with a nitrogen bridgehead including pyrrolo[1,2-a]quinoline, imidazo[1,2-a]quinoline, imidazo[1,5-a]quinoline, pyrrolo[1,2-a]quinazoline, pyrrolo[1,2-c]quinazoline, pyrrolo [2,1-b]quinazoline, and pyrrolo[3,2,1-ij]quinazoline with emphasis on the synthesis, functionalization methods, and applications published in the last 20 years. These N-bridgehead [5,6]-fused ring systems play an important role in the design and synthesis of novel biologically active molecules, catalysts, and fluorescent compounds. The pyrrolo[2,1-b]quinazoline scaffold is a privileged structure present in over 50 alkaloids and in numerous synthetic compounds having a significant range of biological activities. The pyrrolo[1,2-a]quinoline and pyrrolo[1,2-a]quinazoline frameworks have also been isolated from natural sources and display biological activities in diverse areas.