Studies of isomeric phospholes : synthesis and application in transitionmetal and organic catalysis

Abstract

The work described herein encompasses a few topics related to the studies of isomeric phospholes. Phospholes have been explored thoroughly over the past many years. They are now accepted as only weakly aromatic: the aromatic stabilization resulting from electronic delocalization of phosphole’s planar state is not sufficient enough to overcome its intrinsically high inversion barrier of phosphorus. This results in their pyramidal structure when in ground state and a very poor orbital overlap between the phosphorus lone pair np and the π orbitals of the diene unit. Therefore, they seem to resemble more cyclopentadienes than their nitrogen analogues - pyrroles. Though, only recently has the attention been shifted to the phosphole’s isomeric form - phospholene. Due to phosphole’s low aromaticity, there lies the opportunity to switch from slightly aromatic to slightly antiaromatic character of these heterocycles, which in turn changes the chemistry of this species.