Vol.:(0123456789)
Topics in Current Chemistry (2019) 377:35
https://doi.org/10.1007/s41061-019-0266-z
1 3
REVIEW
N‑Heterocyclic Carbene (NHC)/Metal Cooperative Catalysis
Kazunori Nagao
1
· Hirohisa Ohmiya
1
Received: 1 May 2019 / Accepted: 5 November 2019 / Published online: 13 November 2019
© Springer Nature Switzerland AG 2019
Abstract
N-Heterocyclic carbene (NHC) catalysis can access umpolung reactivity of carbonyl
compounds as acyl anions, enolates and homoenolates. Considerable progress has
been made in asymmetric transformation by the introduction of chirality to the NHC
scaffold. However, the single catalyst system has limitations in chemo-, regio- and
stereoselectivity. A solution to these problems has recently emerged with the synergistic combination of NHC catalysis and metal catalysis. A number of NHC/metal
combinations have been found not only to improve reactivity and stereoselectivity,
but also to enable access to unprecedented transformations. This paper highlights
examples of successful asymmetric NHC/metal cooperative catalysis.
Keywords N-Heterocyclic carbene · Umpolung · Lewis acid · Metal catalysis ·
Cooperative catalysis
1 General Introduction
Synergistic (cooperative) catalysis is a synthetic strategy wherein multiple distinct
catalysts activate two different substrates simultaneously, thereby facilitating a single chemical transformation. The development of new reactions by the synergistic
combination of organocatalysis and metal catalysis has seen remarkable progress
over the past decade. Nevertheless, the combination of N-heterocyclic carbene
(NHC) catalysis [1–4], which exhibits a characteristic ability to access umpolung
reactivity, with metal catalysis remains a challenge, due to the difficulty attributed
to the strong propensity of NHCs to bind to metals with high affinity (Fig. 1) [5,
6]. Several groups have recently overcome such problems and reported successful
synergistic NHC/early-metal or late-transition-metal-catalyzed umpolung reactions
* Hirohisa Ohmiya
ohmiya@p.kanazawa-u.ac.jp
1
Division of Pharmaceutical Sciences, Graduate School of Medical Sciences, Kanazawa
University, Kakuma-machi, Kanazawa 920-1192, Japan
Reprinted from the journal
83
Chapter 4 was originally published as Nagao, K. & Ohmiya, H. Topics in Current Chemistry (2019) 377: 35.
https://doi.org/10.1007/s41061-019-0266-z.
Topics in Current Chemistry (2019) 377:35
https://doi.org/10.1007/s41061-019-0266-z
1 3
REVIEW
N‑Heterocyclic Carbene (NHC)/Metal Cooperative Catalysis
Kazunori Nagao
1
· Hirohisa Ohmiya
1
Received: 1 May 2019 / Accepted: 5 November 2019 / Published online: 13 November 2019
© Springer Nature Switzerland AG 2019
Abstract
N-Heterocyclic carbene (NHC) catalysis can access umpolung reactivity of carbonyl
compounds as acyl anions, enolates and homoenolates. Considerable progress has
been made in asymmetric transformation by the introduction of chirality to the NHC
scaffold. However, the single catalyst system has limitations in chemo-, regio- and
stereoselectivity. A solution to these problems has recently emerged with the synergistic combination of NHC catalysis and metal catalysis. A number of NHC/metal
combinations have been found not only to improve reactivity and stereoselectivity,
but also to enable access to unprecedented transformations. This paper highlights
examples of successful asymmetric NHC/metal cooperative catalysis.
Keywords N-Heterocyclic carbene · Umpolung · Lewis acid · Metal catalysis ·
Cooperative catalysis
1 General Introduction
Synergistic (cooperative) catalysis is a synthetic strategy wherein multiple distinct
catalysts activate two different substrates simultaneously, thereby facilitating a single chemical transformation. The development of new reactions by the synergistic
combination of organocatalysis and metal catalysis has seen remarkable progress
over the past decade. Nevertheless, the combination of N-heterocyclic carbene
(NHC) catalysis [1–4], which exhibits a characteristic ability to access umpolung
reactivity, with metal catalysis remains a challenge, due to the difficulty attributed
to the strong propensity of NHCs to bind to metals with high affinity (Fig. 1) [5,
6]. Several groups have recently overcome such problems and reported successful
synergistic NHC/early-metal or late-transition-metal-catalyzed umpolung reactions
* Hirohisa Ohmiya
ohmiya@p.kanazawa-u.ac.jp
1
Division of Pharmaceutical Sciences, Graduate School of Medical Sciences, Kanazawa
University, Kakuma-machi, Kanazawa 920-1192, Japan
Reprinted from the journal
83
Chapter 4 was originally published as Nagao, K. & Ohmiya, H. Topics in Current Chemistry (2019) 377: 35.
https://doi.org/10.1007/s41061-019-0266-z.