Copper-catalyzed [3 + 2]/[3 + 2] carboannulation of dienynes and arylsulfonyl chlorides enabled by Smiles rearrangement: access to cyclopenta[a]indene-fused quinolinones

On one hand, the construction of two fused five-membered carbocyclic rings remains an extremely challenging topic in organic synthesis. On the other hand, transition-metal-catalyzed dienyne cycloaddition reactions have become one of the most powerful methods for the construction of diverse cyclic frameworks. Nevertheless, these methods are limited to noble transition-meal catalysis and non-radical cycloaddition modes. Here, a radical Smiles rearrangement strategy for allowing an unprecedented [3 + 2]/[3 + 2] carboannulation of dienynes with arylsulfonyl chlorides using cheap copper catalysis is described. This cascade method represents a novel cycloaddition mode for dienyne chemistry, which occurs by the sequence of addition of arylsulfonyl radical to a dienyne, a Smiles rearrangement and radical annulation to access cyclopenta[a]indene-fused quinolinones with excellent diastereoselectivity.