Rh-Catalyzed [2 + 2 + 2] Cycloadditions with Benzoquinones: De Novo Access to Naphthoquinones for Lignan and Type II Polyketide Synthesis.

The first examples of Rh-catalyzed [2 + 2 + 2] cycloadditions between diynes and benzoquinones are described. The method enables de novo and step-economical access to challenging naphthoquinones that are of relevance to lignan and type II polyketide synthesis. The value of the chemistry is demonstrated by a short total synthesis of justicidone.