Azafluorenes. Synthesis and transformations

Data on the chemistry of azafluorenes (indenopyridines) over the past 20 years are surveyed. Methods for the synthesis of azafluorene isomers with the nitrogen atom in all the possible positions are considered. The main reactions of azafluorenes are analysed. Their reactivity is determined by the presence and mutual influence of the two fused rings of different natures (benzene and pyridine rings) as well as by the order of conjugation of benzene and pyridine fragments. The main transformations of substituents occupying various positions of the azafluorene system are considered. Data on the natural occurrence of azafluorenes, biological activities of their derivatives, and on the structure and physicochemical properties of azafluorenes and their derivatives are presented.