Aromatic Phosphorus Heterocycles

Phosphorus an element with an electronegativity somewhat less than that of carbon and is an excellent and versatile building block of aromatic systems. Thus, in many systems carbon can be replaced efficiently by phosphorus. The versatility is a consequence of the many different bonding modes available for the pnicogen element. The extent of the aromaticity is different with the different bonding modes, and can also be fine tuned by utilizing various substituents that have inductive or steric effects. It is noteworthy that even small effects can have a large impact on the chemistry of these compounds. Thus, the analysis of subtle changes in aromaticity can be of importance in the future.