Umpolung by N‐Heterocyclic Carbenes: Generation and Reactivity of the Elusive 2,2‐Diamino Enols (Breslow Intermediates)

Abstract

54 years later: Saturated imidazolidin-2-ylidenes react with aldehydes to smoothly produce the elusive 2,2-diamino enols A (“Breslow intermediates”, 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 Breslow intermediates B are accessible by deprotonation of methoxymethyl azolium salts. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.