N‐Heterocyclic Carbene Catalyzed Domino Reactions

Abstract

While organocatalyzed domino reactions or "organocascade catalysis" developed into an important tool in synthetic chemistry during the past decade, the utility of N-heterocyclic carbenes (NHCs) as catalysts in domino reactions has only received growing attention in the past three years. Taking into account the unique activation modes of the substrates by NHC catalysts, it is often difficult to distinguish between a single chemical transformation and a sequential one-pot transformation. Therefore, herein we present a critical consideration of domino, cascade, and tandem catalysis in the case of NHC catalysts and highlight recent publications in this area.

Asymmetric catalysis with N-heterocyclic carbenes as non-covalent chiral templates

“…Extensive research has shown that chiral NHCs are a class of privileged chiral ligands for transition-metal catalysis 3,4 and that they are versatile chiral organocatalysts 5,6 that can generate one enantiomer preferentially in numerous organic transformations 7,8 . NHCs can catalyse chemical bond synthesis because of several unique chemical characteristics: they are strong s-donors 1 and good Brønsted bases, and they have moderate p-acidity 9 .…”

Recent advances on asymmetric Strecker reactions

“…Numerous basic organocatalytic protocols for very efficient and highly stereoselective carbon-carbon and carbon-heteroatom bond formations are now part of the strategic arsenal of synthetic chemistry. 67,68 The Lipton group first reported the chiral diketopiperazine-catalyzed hydrocyanation of aldimines in 1996. 11 They investigated the stereoselective addition of HCN to a variety of imines catalyzed by synthetically obtained diketopiperazine-based organocatalyst 35 (Scheme 34).…”

N-Heterocyclic Carbene Catalyzed Reaction of 2-(2-Aroylvinyl)cinnamalde­hydes with α,β-Unsaturated Imines: An Efficient Method for the Stereoselective Synthesis of Highly Functionalized Indane Derivatives

“…2,8 Cascade reactions catalyzed by N-heterocyclic carbenes (NHCs) have received attention due to the resulting rapid generation of complex products. 9 A few N-heterocyclic carbene catalyzed reactions have been reported to produce different indene or indane derivatives. For example, the cascade reactions of 2-formylcinnamates with imines, phthalaldehydes with imines, and phthalaldehydes with 3-aroylacrylates in the presence of NHC catalysts gave substituted indan-1-ones, 10a-c while NHC-catalyzed reaction of 3,3′-(1,2-phenylene)bis(1-phenylpropenones) with aldehydes produced 1,2,3-trisubstituted indanes.…”