title: Exploiting Acyl and Enol Azolium Intermediates via NHeterocyclic Carbene Catalyzed Reactions of Alpha-Reducible Aldehydes.
abstract: N-heterocyclic carbenes are well known for their role in catalyzing benzoin and Stetter reactions: the generation of acyl anion equivalents from simple aldehydes to react with a variety of electrophiles. However, when an aldehyde bearing a leaving group or unsaturation adjacent to the acyl anion equivalent is subjected to an NHC, a new avenue of reactivity is unlocked, leading to a number of novel transformations which can generate highly complex products from simple starting materials, many of which are assembled through unconventional bond disconnections. The field of these new reactions - those utilizingα-reducible aldehydes to access previously unexplored catalytic intermediates - has expanded rapidly in the past eight years. This review aims to provide the reader with a historical perspective on the underlying discoveries that led to the current state of the art, a mechanistic description of these reactions, and a summary of the recent advances in this area.
authors.forename: Harit U
authors.initials: HU
authors.lastname: Vora
authors.forename: Philip
authors.initials: P
authors.lastname: Wheeler
authors.forename: Tomislav
authors.initials: T
authors.lastname: Rovis
keywords: Acylation; Asymmetric; Homoenolate; N-heterocyclic carbene; Organocatalysis
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