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An Umpolung Reaction of Aldehydes with Arynes
A. T. Biju, F. Glorius*
Westfälische Wilhelms-Universität Münster, Germany
21 December 2010 (online)
Biju and Glorius report an unprecedented N-heterocyclic carbene (NHC) catalyzed hydroacylation of arynes. In this umpolung reaction, various aldehydes 1 are activated via the Breslow intermediate A to react with arynes generated in situ from precursors 2. The authors propose a mechanism involving either a concerted (B) or a stepwise (C → D) addition-protonation sequence. An analogy to the more explored [2+3] cycloadditions of arynes and 1,3-dipoles is invoked for the concerted mechanism. Competition experiments provided insight into the rates of individual steps.