α,β-Unsaturated ketones constitute a versatile building block for the synthesis of complex molecules and efficient methods for their functionalization are of continued interest. In particular the a-arylation of enones is a powerful and ubiquitous transformation, however there exists only one method for direct C–H arylation and it is limited in both practicality and scope. Enone α-arylation is most commonly achieved via a stepwise halogenation/cross-coupling sequence. Although highly enabling, the required pre-functionalization, as well as the use of expensive and toxic catalysts detract from the efficiency and practicality of this approach. Herein, we demonstrate the direct C–H α-arylation of enones via a reductive iodonium-Claisen rearrangement of in situ generated pyridinium silyl enol ethers and I(III) reagents. The method utilizes ArI(OTFA)2 species as the aryl source, which are readily accessed from the parent iodoarenes and tolerant of a wide range of substitution. Furthermore, the arylated products retain the valuable iodide functional handle, and further derivatization to diverse indoles and benzofurans is demonstrated. Mechanistically, the reaction proceeds through formation of an O–I enolonium species followed by reductive iodonium-Claisen rearrangement and this reactivity is contingent on the presence of the b-pyridinium moiety. This method represents an atom and step economical approach to access diverse a-(2-iodo)arylated enone motifs, providing rapid entry to heterocyclic structures and complex molecular architectures.

Direct C–H arylation of enones with ArI(OCOR)2 reagents

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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