Umpolung by N-Heterocyclic Carbenes: Generation and Reactivity of the Elusive 2,2-Diamino Enols (Breslow Intermediates)
作者:Albrecht Berkessel、Silvia Elfert、V. Reddy Yatham、Jörg-M. Neudörfl、Nils E. Schlörer、J. Henrique Teles
DOI:10.1002/anie.201205878
日期:2012.12.3
Saturated imidazolidin‐2‐ylidenes react with aldehydes to smoothly produce the elusive 2,2‐diamino enols A (“Breslowintermediates”, first postulated in 1958) of carbene‐catalyzed umpolung reactions. The 2,2‐diamino enols A react with additional aldehyde in a cross‐benzoin reaction. The methylated Breslowintermediates B are accessible by deprotonation of methoxymethyl azolium salts.