Low-Temperature, Transition-Metal-Free Cross-Dehydrogenative Coupling Protocol for the Synthesis of 3,3-Disubstituted Oxindoles
James R. Donald, Richard J. K. Taylor* and Wade F. Petersen*
*Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.; Department of Chemistry, University of Cape Town, Rondebosch, 7700, South Africa, Email: richard.tayloryork.ac.uk, wade.petersenuct.ac.za
J. R. Donald, R. J. K. Taylor, W. F. Petersen, J. Org. Chem., 2017, 82, 11288-11294.
DOI: 10.1021/acs.joc.7b02085 (free Supporting Information)
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A cross-dehydrogenative coupling enable a low-temperature procedure for the synthesis of 3,3-disubstituted 2-oxindoles. The use of a strong, nonreversible base effects a dramatic drop in reaction temperature. With iodine as an "oxidant", new evidence suggests that this transformation may occur via a transiently stable iodinated intermediate rather than by direct single-electron oxidation.
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J. E. M. N. Klein, A. Perry, D. S. Pugh, R. J. K. Taylor, Org. Lett., 2010, 12, 3446-3449.