Poly(<i>para</i>-arylene)s via [2+2+2]

We report a versatile new synthetic route to poly­(<i>para</i>-phenylene)­s (PPPs) and related poly­(<i>para</i>-arylene)­s containing high degrees of substitution not readily available by other methods. Our method transforms highly soluble, alkyne-containing polymers into PPPs via high-yielding, transition metal-mediated [2+2+2] cyclizations