Aromatizing Ethers

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Science  10 Aug 2012:
Vol. 337, Issue 6095, pp. 625
DOI: 10.1126/science.337.6095.625-a

Aryl ethers are common motifs in the production of commercially important organic compounds. Generally, they are prepared from precursors that already contain the aromatic ring (either by coupling a carbon center to a phenolic oxygen or coupling an alcohol to an aryl carbon). Simon et al. have developed a complementary approach that combines an alcohol with a cyclohexenone derivative and then aromatizes the framework after carbon-oxygen bond formation. They initially used cupric chloride as a coupling agent, together with O2 as an oxidant. Adding an organic radical source as co-catalyst and replacing the counterions with triflate together with potassium iodide reduced the necessary copper loading to 10%. The reaction tolerates a range of functional groups, including esters, alkynes (both internal and terminal), and aryl iodides poised for further elaboration by cross-coupling techniques. Control experiments preclude the intermediacy of phenol, thus implicating a mechanism in which alcohol addition to the carbonyl precedes hydrogen abstractions that produce the aromatic ring.

Angew. Chem. Int. Ed. 51, 7537 (2012).

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