Synthesis of Polycyclic Phosphacycles via 1-Phosphafulvene

1-Phosphafulvenes are unique in their cycloaddition reactions, which act as 2 π , 4 π , and 6 π systems and provide versatile and powerful approaches to various polycyclic systems. The reaction of 1-phosphafulvene with 1,4-benzoquinone and N-phenylmaleimide upon heating provided phosphapolycyclic rings in moderate to good yields. The possible mechanism included an oxidative addition of 1-phosphafulvene with 1,4-benzoquinone and successive Diels-Alder reactions with N -phenylmaleimide. The exocyclic C ＝ C bond of 1-phosphafulvene is cruial to this reaction.