Phosphorus-Substituted Azulenes Accessed via Direct Hafner Reaction of a Phosphino Cyclopentadienide

The Hafner azulene synthesis may be applied to the direct synthesis of phosphorus-substituted azulenes, when a phosphinocyclopentadienide is used as one of the reactants. The azulenyl phosphines produced in this fashion are preferentially isolated as the corresponding phosphine oxides or phosphine borane adducts.