Hexadehydro Diels–Alder/Alkynyliodanation Cascade: A Highly Regioselective and Expedient Entry to Polycyclic Aromatics

We report here a cascade process that integrates the hexadehydro Diels–Alder (HDDA) reaction with alkynyliodanation of the resulting aryne, enabling the efficient synthesis of highly substituted aryl-λ3-iodanes. By simply heating a mixture of a tetrayne, consisting of tethered 1,3-diynes, and an alkynylbenziodoxole, the tetrayne-derived aryne undergoes highly regioselective insertion into the alkynyl–iodine(III) bond, producing a 1,4-dialkynyl-2-iodanyl-3-arylbenzene derivative in good yield. Notably, the observed regioselectivity contrasts with the typical regioselectivity patterns reported in related HDDA/aryne trapping reactions, likely due to steric factors influencing the four-centered transition states. The unique regiochemical arrangement of the iodanyl, alkynyl, and aryl substituents offers a versatile platform for subsequent π-extension reactions. These downstream transformations enable the divergent construction of polyaromatic frameworks, such as helicenes and cyclopenta[cd]pyrenes, underscoring the utility of aryne carboiodanation in complex aromatic synthesis.