Heavy\nHeterodendralenes: Structure and Reactivity\nof Phosphabora[3]dendralenes

The incorporation\nof phosphorus and boron into [3]dendralenes provides\naccess to heavy heterodendralenes, a new class of main-group precursor\nto “doped” polycyclic hydrocarbons. [<i>n</i>]Dendralenes are a core class of unsaturated hydrocarbons built from\ngeminally connected polyenes; the resulting arrangement of conjugated\nCC bonds enables [<i>n</i>]dendralenes to undergo\nreactions that allow rapid access to complex polycyclic compounds.\nThe increasing technological and synthetic importance of main-group-containing\npolycyclic hydrocarbons and their analogues makes new routes to access\nsuch systems highly attractive. Here we report the preparation of\nthe first heavy heterodendralenes in the form of phosphorus- and boron-containing\n[3]dendralenes, prepared by a ring-opening reaction of a 1,2-phosphaborete.\nWe reveal the electronic effect of P/B incorporation and demonstrate\nthat, like their hydrocarbon analogues, phosphabora[3]dendralenes\nundergo diene-transmissive cycloaddition chemistry.