1 3
Topics in Current Chemistry (2019) 377:35
oxidant. Alternatively, Wang’s group reported the same transformation using only a
ruthenium salt with labile ligands as the electron transfer mediator [38]. This report
is a rare example of NHC/metal cooperative catalysis using a coordinatively unsaturated late-transition-metal salt.
4 Summary and Future Outlook
In this paper, recent progress in NHC/metal cooperative catalysis has been demonstrated. Both Lewis acids and late transition metals can participate in the NHC
catalytic cycle to enhance selectivity or develop new reactivity. However, in both
cases, the bond-forming process depends on a two-electron reaction manifold via
homoenolate and acyl azolium as key intermediates. Therefore, the reaction suffers
from the steric and electronic natures of the electrophiles. We recently demonstrated
that the Breslow intermediate-derived radical could participate in radical–radical
coupling with the alkyl radical in the bond-forming process [39–41]. This report
showed one of the new chemical spaces wherein the metal co-catalyst controls the
reactivity and stereoselectivity of the NHC-bound radical. This approach can lead to
the development of NHC-catalyzed highly selective and universal bond formation
using simple substrates.
References
1. Enders D, Niemeier O, Henseler A (2007) Organocatalysis by N-heterocyclic carbenes. Chem Rev
107:5606–5655
2. Hopkinson MN, Richter C, Schedler M, Glorius F (2014) An overview of N-heterocyclic carbenes.
Nature 510:485–496
3. Flanigan DM, Romanov-Michailidis F, White NA, Rovis T (2015) Organocatalytic reactions enabled by N-heterocyclic carbenes. Chem Rev 115:9307–9387
4. Biju AT (2019) N-Heterocyclic carbenes in organocatalysis. Wiley-VCH, Weinheim
5. Díez-Gonzaĺez S, Marion N, Nolan SP (2009) N-Heterocyclic carbenes in late transition metal catalysis. Chem Rev 109:3612–3676
6. Janssen-Müller D, Schlepphorst C, Glorius F (2017) Chem Soc Rev 46:4845–4854
7. Cohen DT, Scheidt KA (2012) Cooperative Lewis acid/N-heterocyclic carbene catalysis. Chem Sci.
3:53–57
8. Wang MH, Scheidt KA (2016) Cooperative catalysis and activation with N-heterocyclic carbenes.
Angew Chem Int Ed 55:14912–14922
9. Cardinal-David B, Raup DEA, Scheidt KA (2010) Cooperative N-heterocyclic carbene/Lewis
acid catalysis for highly stereoselective annulation reactions with homoenolates. J Am Chem Soc
132:5345–5347
10. Raup DEA, Cardinal-David B, Holte D, Scheidt KA (2010) Cooperative catalysis by carbenes and
Lewis acids in a highly stereoselective route to γ-lactams. Nat Chem 2:766–771
11. Wang ZY, Ding Y-L, Wang G, Cheng Y (2016) Chiral N-heterocyclic carbene/Lewis acid cooperative catalysis of the reaction of 2-aroylvinylcinnamaldehydes: a switch of the reaction pathway by
Lewis acid activation. Chem Commun 52:788–791
12. Phillips EM, Wadamoto M, Chan A, Scheidt KA (2007) A highly enantioselective intramolecular
Michael reaction catalyzed by N-heterocyclic carbenes. Angew Chem Int Ed 46:3107–3110
13. Dugal-Tessier J, O’bryan EA, Schroeder TBH, Cohen DT, Scheidt KA (2012) An N-heterocyclic
carbene/Lewis acid strategy for the stereoselective synthesis of spirooxindole lactones. Angew
Chem Int Ed 51:4963–4967
Reprinted from the journal
95
Topics in Current Chemistry (2019) 377:35
oxidant. Alternatively, Wang’s group reported the same transformation using only a
ruthenium salt with labile ligands as the electron transfer mediator [38]. This report
is a rare example of NHC/metal cooperative catalysis using a coordinatively unsaturated late-transition-metal salt.
4 Summary and Future Outlook
In this paper, recent progress in NHC/metal cooperative catalysis has been demonstrated. Both Lewis acids and late transition metals can participate in the NHC
catalytic cycle to enhance selectivity or develop new reactivity. However, in both
cases, the bond-forming process depends on a two-electron reaction manifold via
homoenolate and acyl azolium as key intermediates. Therefore, the reaction suffers
from the steric and electronic natures of the electrophiles. We recently demonstrated
that the Breslow intermediate-derived radical could participate in radical–radical
coupling with the alkyl radical in the bond-forming process [39–41]. This report
showed one of the new chemical spaces wherein the metal co-catalyst controls the
reactivity and stereoselectivity of the NHC-bound radical. This approach can lead to
the development of NHC-catalyzed highly selective and universal bond formation
using simple substrates.
References
1. Enders D, Niemeier O, Henseler A (2007) Organocatalysis by N-heterocyclic carbenes. Chem Rev
107:5606–5655
2. Hopkinson MN, Richter C, Schedler M, Glorius F (2014) An overview of N-heterocyclic carbenes.
Nature 510:485–496
3. Flanigan DM, Romanov-Michailidis F, White NA, Rovis T (2015) Organocatalytic reactions enabled by N-heterocyclic carbenes. Chem Rev 115:9307–9387
4. Biju AT (2019) N-Heterocyclic carbenes in organocatalysis. Wiley-VCH, Weinheim
5. Díez-Gonzaĺez S, Marion N, Nolan SP (2009) N-Heterocyclic carbenes in late transition metal catalysis. Chem Rev 109:3612–3676
6. Janssen-Müller D, Schlepphorst C, Glorius F (2017) Chem Soc Rev 46:4845–4854
7. Cohen DT, Scheidt KA (2012) Cooperative Lewis acid/N-heterocyclic carbene catalysis. Chem Sci.
3:53–57
8. Wang MH, Scheidt KA (2016) Cooperative catalysis and activation with N-heterocyclic carbenes.
Angew Chem Int Ed 55:14912–14922
9. Cardinal-David B, Raup DEA, Scheidt KA (2010) Cooperative N-heterocyclic carbene/Lewis
acid catalysis for highly stereoselective annulation reactions with homoenolates. J Am Chem Soc
132:5345–5347
10. Raup DEA, Cardinal-David B, Holte D, Scheidt KA (2010) Cooperative catalysis by carbenes and
Lewis acids in a highly stereoselective route to γ-lactams. Nat Chem 2:766–771
11. Wang ZY, Ding Y-L, Wang G, Cheng Y (2016) Chiral N-heterocyclic carbene/Lewis acid cooperative catalysis of the reaction of 2-aroylvinylcinnamaldehydes: a switch of the reaction pathway by
Lewis acid activation. Chem Commun 52:788–791
12. Phillips EM, Wadamoto M, Chan A, Scheidt KA (2007) A highly enantioselective intramolecular
Michael reaction catalyzed by N-heterocyclic carbenes. Angew Chem Int Ed 46:3107–3110
13. Dugal-Tessier J, O’bryan EA, Schroeder TBH, Cohen DT, Scheidt KA (2012) An N-heterocyclic
carbene/Lewis acid strategy for the stereoselective synthesis of spirooxindole lactones. Angew
Chem Int Ed 51:4963–4967
Reprinted from the journal
95