N-Heterocyclic Carbene Organocatalysis: Activation Modes and Typical Reactive Intermediates
Xingkuan Chen
Department of Chemistry, Jinan University, Guangzhou, Guangdong, 510632 China
ǂX.C.and H.W. contributed equally to this work.
Search for more papers by this authorHongling Wang
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
ǂX.C.and H.W. contributed equally to this work.
Search for more papers by this authorZhichao Jin
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
Search for more papers by this authorCorresponding Author
Yonggui Robin Chi
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore, 637371 Singapore
E-mail: [email protected]Search for more papers by this authorXingkuan Chen
Department of Chemistry, Jinan University, Guangzhou, Guangdong, 510632 China
ǂX.C.and H.W. contributed equally to this work.
Search for more papers by this authorHongling Wang
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
ǂX.C.and H.W. contributed equally to this work.
Search for more papers by this authorZhichao Jin
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
Search for more papers by this authorCorresponding Author
Yonggui Robin Chi
Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang, Guizhou, 550025 China
Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore, 637371 Singapore
E-mail: [email protected]Search for more papers by this authorAbstract
N-Heterocyclic carbene (NHC) organocatalysis has been developed as an important approach in modern organic synthesis. Versatile activation modes within NHC organocatalysis have been established with countless transformations being realized in both efficient and selective fashion. We would like to provide an overview on the key progresses achieved within this field in the past two decades. Since numerous excellent reviews have been documented within this area, we will mainly focus on the scientific development of this research field based on the basic reaction modes and typical reaction intermediates.
References
- 1(a) Igau, A.; Grutzmacher, H.; Baceiredo, A.; Bertrand, G. Analogous α,α'-bis-Carbenoid Triply Bonded Species: Synthesis of a Stable λ3-Phosphinocarbene-λ5-Phosphaacetylene. J. Am. Chem. Soc. 1988, 110, 6463-6466; (b) Igau, A.; Baceiredo, A.; Trinquier, G.; Bertrand, G. [Bis(diisopropylamino)phosphino]trimethylsilylcarbene: A Stable Nucleophilic Carbene. Angew. Chem. Int. Ed. 1989, 28, 621–622.
- 2 Arduengo, A. J.; Harlow, R.; Kline, M. A Stable Crystalline Carbene. J. Am. Chem. Soc. 1991, 113, 361–363.
- 3For reviews of NHC in transition metal catalysis, see: (a) Doddi, A.; Peters, M.; Tamm, M. N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry. Chem. Rev. 2019, 119, 6994–7112; (b) Peris, E. Smart N-Heterocyclic Carbene Ligands in Catalysis. Chem. Rev. 2018, 118, 9988–10031; (c) Gan, M.-M.; Liu, J.-Q.; Zhang, L.; Wang, Y.-Y.; Hahn, F. E.; Han, Y.-F. Preparation and Post-Assembly Modification of Metallosupramolecular Assemblies from Poly(N-Heterocyclic Carbene) Ligands. Chem. Rev. 2018, 118, 9587–9641.
- 4(a) Bourissou, D.; Guerret, O.; Gabbaï, F. P.; Bertrand, G. Stable Carbenes. Chem. Rev. 2000, 100, 39–92; (b) Frémonta, P.; Marionb, N.; Nolan, S. P. Carbenes: Synthesis, Properties, and Organometallic Chemistry. Coord. Chem. Rev. 2009, 253, 862–892.
- 5(a) Benhamou, L.; Chardon, E.; Lavigne, G.; Stéphane, B.-L.; César, V. Synthetic Routes to N-Heterocyclic Carbene Precursors. Chem. Rev. 2011, 111, 2705–2733; (b) Flanigan, D. M.; Fedor, R.-M.; White, N. A.; Rovis, T. Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes. Chem. Rev. 2015, 115, 9307–9387.
- 6Reviews on the carbene history: (a) Arduengo III, A. J.; Krafczyk, R. Auf der Suchenach Stabilen Carbenen. Chem. Unserer Zeit. 1998, 32, 6–14;
(b) Garrison, J. C.; Youngs, W. J. Ag(I) N-Heterocyclic Carbene Complexes: Synthesis, Structure, and Application. Chem. Rev. 2005, 105, 3978–4008;
(c) Nolan, S. P. N-Heterocyclic Carbenes in Synthesis, Wiley-VCH, Weinheim, Germany, 2006, pp. 1–304.
10.1002/9783527609451 Google Scholar
- 7 Enders, D.; Breuer, K.; Raabe, J.; Runsink, Teles, J. H.; Melder, J. P.; Ebel, K.; Brode, S. Preparation, Structure, and Reactivity of 1,3,4-Triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene, a New Stable Carbene. Angew. Chem. Int. Ed. 1995, 34, 1021–1023.
- 8 Hopkinson, M. N.; Richter, C.; Schedler, M.; Glorius, F. An Overview of N-Heterocyclic Carbenes. Nature 2014, 510, 485–496.
- 9 Ukai, T.; Tanaka, S.; Dokawa, S. A New Catalyst for Acyloin Condensation. J. Pharm. Soc. Jpn. 1943, 63, 296–304.
- 10 Breslow, R. On the Mechanism of Thiamine Action. IV1 Evidence from Studies on Model Systems. J. Am. Chem. Soc. 1958, 80, 3719–3726.
- 11 Sheehan, J. C.; Hunneman, D. H. Homogeneous Asymmetric Catalysis. J. Am. Chem. Soc. 1966, 88, 3666–3667.
- 12 Bugaut, X.; Glorius, F. Organocatalytic Umpolung: N-Heterocyclic Carbenes and Beyond. Chem. Soc. Rev. 2012, 41, 3511–3522.
- 13 Seebach, D. Methods of Reactivity Umpolung. Angew. Chem. Int. Ed. 1979, 18, 239–258.
- 14(a) Jordan, F.; Kudzin, Z. H.; Rios, C. B. Generation and Physical Properties of Enamines Related to the Key Intermediate in Thiamin Diphosphate-Dependent Enzymic Pathways. J. Am. Chem. Soc. 1987, 109, 4415–4416; (b) Simonovic, S.; Frison, J.-C.; Koyuncu, H.; Whitwood, A. C.; Douthwaite, R. E. Addition of N-Heterocyclic Carbenes to Imines: Phenoxide Assisted Deprotonation of an Imidazolium Moiety and Generation of Breslow Intermediates Derived from Imines. Org. Lett. 2009, 11, 245–247; (c) Lai, W.; Li, C.; Chen, H.; Shaik, S. Hydrogen-Abstraction Reactivity Patterns from A to Y: The Valence Bond Way. Angew. Chem. Int. Ed. 2012, 51, 5563–5570; (d) Berkessel, A.; Elfert, S.; Yatham, V. R.; Neudörfl, J.-M.; Schlörer, N. E.; Teles, J. H. Umpolung by N-Heterocyclic Carbenes: Generation and Reactivity of the Elusive 2,2-Diamino Enols (Breslow Intermediates). Angew. Chem. Int. Ed. 2012, 51, 12370–12374.
- 15 DiRocco, D. A.; Oberg, K. M.; Rovis, T. Isolable Analogues of the Breslow Intermediate Derived from Chiral Triazolylidene Carbenes. J. Am. Chem. Soc. 2012, 134, 6143–6145.
- 16 Thai, K.; Sánchez-Larios, E.; Gravel, M. Carbene Catalysts. In Comprehensive Enantioselective Organocatalysis: Catalysts, Reactions, and Applications, Ed.: Prter, I. D., Wiley-VCH Verlag GmbH & Co. KGaA, 2013, pp. 495–522.
- 17 For NHC as organocatalysis reviews, see: (a) Enders, D.; Niemeier, O.; Henseler, A. Organocatalysis by N-Heterocyclic Carbenes. Chem. Rev. 2007, 107, 5606–5655; (b) Bugaut, X. Benzoin and Aza-Benzoin. In Comprehensive Organic Synthesis, 2nd ed., Oxford, UK, 2014, pp. 424−470; and reference [5].
- 18(a) Enders D.; Breuer K.; Teles J. H. A Novel Asymmetric Benzoin Reaction Catalyzed by a Chiral Triazolium Salt. Preliminary communication. Helv. Chim. Acta 1996
79
1217–1221;
(b) Knight R. L.; Leeper
F. J. Comparison of Chiral Thiazolium and Triazolium Salts as Asymmetric Catalysts for the Benzoin Condensation. J. Chem. Soc.
Perkin Trans. 1998
29
1891–1894;
10.1039/a803635g Google Scholar(c) Enders D.; Kallfass U. An Efficient Nucleophilic Carbene Catalyst for the Asymmetric Benzoin Condensation. Angew. Chem. Int. Ed. 2002 41 1743–1745;10.1002/1521-3773(20020517)41:10<1743::AID-ANIE1743>3.0.CO;2-Q CAS PubMed Web of Science® Google Scholar(d) Ma Y.; Wei S.; Wu J.; Yang F.; Liu B.; Lan J.; Yang S.; You J. From Mono-Triazolium Salt to Bis-Triazolium Salt: Improvement of the Asymmetric Intermolecular Benzoin Condensation. Adv. Synth. Catal. 2008 350 2645–2651; (e) Baragwanath L.; Rose C. A.; Zeitler K.; Connon S. J. Highly Enantioselective Benzoin Condensation Reactions Involving a Bifunctional Protic Pentafluorophenyl- Substituted Triazolium Precatalyst. J. Org. Chem. 2009 74 9214–9217; (f) Rafiński Z.; Kozakiewicz A.; Rafińska K. Highly Efficient Synthesis of Spirocyclic (1R)-Camphor-Derived Triazolium Salts: Application in the Catalytic Asymmetric Benzoin Condensation. Tetrahedron 2014 70 5739–5745
- 19 Cookson, R. C.; Lane, R. M. Conversion of Dialdehydes into Cyclic α-Ketols by Thiazolium Salts: Synthesis of Cyclic 2-Hydroxy-2- Enones. J. Chem. Soc., Chem. Commun. 1976, 804–805.
- 20 Stetter, H.; Daembkes, G. Über die präparative Nutzung der Thiazoliumsalz-katalysierten Acyloin-und Benzoin-Bildung; II1. Herstellung Unsymmetrischer Acyloine und α-Diketone. Synthesis 1977, 403–404.
- 21(a) Matsumoto, T.; Ohishi, M.; Inoue, S. Selective Cross-Acyloin Condensation Catalyzed by Thiazolium salt. Formation of 1-Hydroxy 2-one from Formaldehyde and Other Aldehydes. J. Org. Chem. 1985, 50, 603–606; (b) Rose, A. C.; Gundala, S.; Connon, S. J.; Zeitler, K. Chemoselective Crossed Acyloin Condensations: Catalyst and Substrate Control. Synthesis 2011, 190–198; (c) Piel, I.; Pawelczyk, M. D.; Hirano, K.; Fröhlich, R.; Glorius, F. A Family of Thiazolium Salt Derived N-Heterocyclic Carbenes (NHCs) for Organocatalysis: Synthesis, Investigation and Application in Cross-Benzoin Condensation. Eur. J. Org. Chem. 2011, 2011, 5475–5484; (d) Kuhl, N.; Glorius, F. Direct and Efficient N-Heterocyclic Carbene-Catalyzed Hydroxymethylation of Aldehydes. Chem. Commun. 2011, 47, 573–575; (e) Langdon, S. M.; Wilde, M. M. D.; Thai, K.; Gravel, M. Chemoselective N-Heterocyclic Carbene-Catalyzed Cross-Benzoin Reactions: Importance of the Fused Ring in Triazolium Salts. J. Am. Chem. Soc. 2014, 136, 7539–7542.
- 22(a) Jin, M. Y.; Kim, S. M.; Han, H.; Ryu, D. H.; Yang, J. W. Switching Regioselectivity in Crossed Acyloin Condensations between Aromatic Aldehydes and Acetaldehyde by Altering N-Heterocyclic Carbene Catalysts. Org. Lett. 2011, 13, 880–883; (b) Liu, R.; Yu, C.; Xiao, Z.; Li, T.; Wang, X.; Xie, Y.; Yao, C. NHC-Catalyzed Oxidative γ-Addition of α,β-Unsaturated Aldehydes to Isatins: a High-Efficiency Synthesis of Spirocyclic Oxindole-Dihydropyranones. Org. Biomol. Chem. 2014, 12, 1547–1550.
- 23 Hachisu, Y.; Bode, J. W.; Suzuki, K. Catalytic Intramolecular Crossed Aldehyde-Ketone Benzoin Reactions: A Novel Synthesis of Functionalized Preanthraquinones. J. Am. Chem. Soc. 2003, 125, 8432–8433.
- 24(a) Takikawa, H.; Hachisu, Y.; Bode, J. W.; Suzuki, K. Catalytic Enantioselective Crossed Aldehyde-Ketone Benzoin Cyclization Angew. Chem. Int. Ed. 2006, 45, 3492–3494; (b) Enders, D.; Niemeier, O.; Balensiefer, T. Asymmetric Intramolecular Crossed-Benzoin Reactions by N-Heterocyclic Carbene Catalysis. Angew. Chem. Int. Ed. 2006, 45, 1463–1467; (c) Li, Y.; Feng, Z.; You, S.-L. D-Camphor-Derived Triazolium Salts for Catalytic Intramolecular Crossed Aldehyde–Ketone Benzoin Reactions. Chem. Commun. 2008, 39, 2263–2265.
- 25 Ema, T.; Oue, Y.; Akihara, K.; Miyazaki, Y.; Sakai, T. Stereoselective Synthesis of Bicyclic Tertiary Alcohols with Quaternary Stereocenters via Intramolecular Crossed Benzoin Reactions Catalyzed by N-Heterocyclic Carbenes. Org. Lett. 2009, 11, 4866–4869.
- 26 Goodman, C. G.; Johnson, J. S. Dynamic Kinetic Asymmetric Cross-Benzoin Additions of β-Stereogenic α-Keto Esters. J. Am. Chem. Soc. 2014, 136, 14698–14701.
- 27 Zhang, G.; Yang, S.; Zhang, X.; Lin, Q.; Das, D. K.; Liu, J.; Fang, X. Dynamic Kinetic Resolution Enabled by Intramolecular Benzoin Reaction: Synthetic Applications and Mechanistic Insights. J. Am. Chem. Soc. 2016, 138, 7932–7938.
- 28(a) Lathrop, S. P.; Rovis, T. Asymmetric Synthesis of Functionalized Cyclopentanones via a Multicatalytic Secondary Amine/N-Heterocyclic Carbene Catalyzed Cascade Sequence. J. Am. Chem. Soc. 2009, 131, 13628–13630; (b) Ozboya, K. E.; Rovis, T. Enamine/Carbene Cascade Catalysis in the Diastereo- and Enantioselective Synthesis of Functionalized Cyclopentanones. Chem. Sci. 2011, 2, 1835–1838
- 29(a) Enders, D.; Grossmann, A.; Huang, H.; Raabe, G. Dual Secondary Amine/N-Heterocyclic Carbene Catalysis in the Asymmetric Michael/Cross-Benzoin Cascade Reaction of β-Oxo Sulfones with Enals Eur. J. Org. Chem. 2011, 2011, 4298–4301; (b) Liu, Y.; Nappi, M.; Eduardo, C. E.-A.; Melchiorre, P. Multicatalytic Asymmetric Synthesis of Complex Tetrahydrocarbazoles via a Diels–Alder/Benzoin Reaction Sequence. Org. Lett. 2012, 14, 1310–1313; (c) Ma, C.; Gu, J.; Teng, B.; Zhou, Q.-Q.; Li, R.; Chen, Y.-C. 1-Azadienes as Regio- and Chemoselective Dienophiles in Aminocatalytic Asymmetric Diels–Alder Reaction. Org. Lett. 2013, 15, 6206–6209.
- 30(a) Castells, J.; López-Calahorra, F.; Bassedas, M.; Urrios, P. A New Thiazolium Salt-Catalyzed Synthesis of α-Aminoketones from Aldehydes and Iminium Salts. Synthesis 1988, 314–315; (b) Murry, J. A.; Frantz, D. E.; Soheili, A.; Tillyer, R.; Grabowski, E. J. J.; Reider, P. J. Synthesis of α-Amido Ketones via Organic Catalysis: Thiazolium- Catalyzed Cross-Coupling of Aldehydes with Acylimines. J. Am. Chem. Soc. 2001, 123, 9696–9697; (c) Mennen, S. M.; Gipson, J. D.; Kim, Y. R.; Miller, S. J. Thiazolylalanine-Derived Catalysts for Enantioselective Intermolecular Aldehyde−Imine Cross-Couplings. J. Am. Chem. Soc. 2005, 127, 1654–1655; (d) Li, G.-Q.; Dai, L.-X.; You, S.-L. Thiazolium-Derived N-Heterocyclic Carbene-Catalyzed Cross-Coupling of Aldehydes with Unactivated Imines. Chem. Commun. 2007, 8, 852–854; (e) DiRocco, D. A.; Rovis, T. Catalytic Asymmetric Cross- Aza-Benzoin Reactions of Aliphatic Aldehydes with N-Boc-Protected Imines. Angew. Chem. Int. Ed. 2012, 51, 5904–5906; (f) Uno, T.; Kobayashi, Y.; Takemoto, Y. N-Heterocyclic Carbene-Catalyzed Direct Cross-Aza-Benzoin Reaction: Efficient Synthesis of α-Amino-β- Keto Esters. Beilstein J. Org. Chem. 2012, 8, 1499–1504; (g) Enders, D.; Henseler, A.; Lowins, S. N-Heterocyclic Carbene Catalyzed Nucleophilic Acylation of Trifluoromethyl Ketimines. Synthesis 2009, 41, 4125–4128; (h) Sun, L.-H.; Liang, Z.-Q.; Jia, W.-Q.; Ye, S. Enantioselective N-Heterocyclic Carbene Catalyzed Aza-Benzoin Reaction of Enals with Activated Ketimines. Angew. Chem. Int. Ed. 2013, 52, 5803–5806; (i) Xu, J.; Mou, C.; Zhu, T.; Song, B.-A.; Chi, Y. R. N-Heterocyclic Carbene-Catalyzed Chemoselective Cross-Aza-Benzoin Reaction of Enals with Isatin-Derived Ketimines: Access to Chiral Quaternary Aminooxindoles. Org. Lett. 2014, 16, 3272–3275.
- 31 Wilde, M. M. D.; Gravel, M. Bis(amino)cyclopropenylidene (BAC) Catalyzed Aza-Benzoin Reaction. Org. Lett. 2014, 16, 5308–5311.
- 32(a) Stetter, H.; Schreckenberg, M. A New Method for Addition of Aldehydes to Activated Double Bonds. Angew. Chem. Int. Ed. 1973, 12, 81–81; (b) Stetter, H.; Kuhlmann, H. Addition of Aliphatic Aldehydes to Activated Double Bonds. Angew. Chem. Int. Ed. 1974, 13, 539–539; (c) Stetter, H.; Kuhlmann, H. Addition Aliphatischer, Heterocyclischer und Aromatischer Aldehyde an Butenon. Chem. Ber. 1976, 109, 3426–3431; (d) Stetter, H. Catalyzed Addition of Aldehydes to Activated Double Bonds-A New Synthetic Approach. Angew. Chem. Int. Ed. 1976, 15, 639–647.
- 33 Ciganek, E. Esters of 2,3-Dihydro-3-oxobenzofuran-2-acetic Acid and 3,4-Dihydro-4-oxo-2H-1-benzopyran-3-acetic Acid by Intramolecular Stetter Reactions. Synthesis 1995, 1311–1314.
- 34 Enders, D.; Breuer, K.; Runsink, J.; Teles, J. H. The First Asymmetric Intramolecular Stetter Reaction. Preliminary Communication. Helv. Chim. Acta 1996, 79, 1899–1902.
- 35(a) Kerr, M. S.; Alaniz, J. R.; Rovis, T. A Highly Enantioselective Catalytic Intramolecular Stetter Reaction. J. Am. Chem. Soc. 2002, 124, 10298–10299; (b) Kerr, M. S.; Rovis, T. Enantioselective Synthesis of Quaternary Stereocenters via a Catalytic Asymmetric Stetter Reaction. J. Am. Chem. Soc. 2004, 126, 8876–8877; (c) Steven, M. M.; Jarred, T. B.; Michelle, B. T. D.; Jason, E. I.; Miller, S. J. A Peptide- Catalyzed Asymmetric Stetter Reaction. Chem. Commun. 2005, 2, 195–197; (d) Jia, M.-Q.; Li, Y.; Rong, Z.-Q.; You, S.-L. Synthesis of (1R,2R)-DPEN-Derived Triazolium Salts and Their Application in Asymmetric Intramolecular Stetter Reactions. Org. Biomol. Chem. 2011, 9, 2072–2074; (e) Rong, Z.-Q.; Li, Y.; Yang, G.-Q.; You, S.-L. δ-Camphor-Derived Triazolium Salts for Enantioselective Intramolecular Stetter Reactions. Synlett 2011, 1033–1037; (f) Soeta, T.; Tabatake, Y.; Ukaji, Y. An Asymmetric Intramolecular Stetter Reaction Catalyzed by a Chiral Triazolium Precatalyst Bearing a Pyridine Moiety. Tetrahedron 2012, 68, 10188–10193; (g) Rafiński, Z.; Kozakiewicz, A.; Rafińska, K. (−)-β-Pinene-Derived N-Heterocyclic Carbenes: Application to Highly Enantioselective Intramolecular Stetter Reaction. ACS Catal. 2014, 4, 1404–1408.
- 36Dalko, P. I. Comprehensive Enantioselective Organocatalysis: Catalysts, Reactions, and Applications, 1st ed., Wiley-VCH Verlag GmbH & Co. KGaA, 2013, pp. 495–522.
- 37 Enders, D.; Han, J.; Henseler, A. Asymmetric Intermolecular Stetter Reactions Catalyzed by a Novel Triazolium Derived N-Heterocyclic Carbene. Chem. Commun. 2008, 3989–3991.
- 38(a) Liu, Q.; Perreault, S.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reaction of Glyoxamides with Alkylidenemalonates. J. Am. Chem. Soc. 2008, 130, 14066–14067; (b) Liu, T.; Rovis, T. Enantio- and Diastereoselective Intermolecular Stetter Reaction of Glyoxamide and Alkylidene Ketoamides. Org. Lett. 2009, 11, 2856–2859; (c) DiRocco, D. A.; Oberg, K. M.; Dalton, D. M.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reaction of Heterocyclic Aldehydes with Nitroalkenes: Backbone Fluorination Improves Selectivity. J. Am. Chem. Soc. 2009, 131, 10872–10874; (d) DiRocco, D. A.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reaction of Enals with Nitroalkenes: Enhancement of Catalytic Efficiency through Bifunctional Additives. J. Am. Chem. Soc. 2011, 133, 10402–10405; (e) DiRocco, D. A.; Noey, E. L.; Houk, K. N.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reactions of Enolizable Aldehydes with Nitrostyrenes: Computational Study Provides Insight into the Success of the Catalyst. Angew. Chem. Int. Ed. 2012, 51, 2391–2394; (f) Jousseaume, T.; Wurz, N. E.; Glorius, F. Highly Enantioselective Synthesis of α-Amino Acid Derivatives by an NHC-Catalyzed Intermolecular Stetter Reaction. Angew. Chem. Int. Ed. 2011, 50, 1410–1414; (g) Fang, X.; Chen, X.; Lv, H.; Chi, Y. R. Enantioselective Stetter Reactions of Enals and Modified Chalcones Catalyzed by N-Heterocyclic Carbenes. Angew. Chem. Int. Ed. 2011, 50, 11782–11785; (h) Eduardo, S.-L.; Thai, K.; Bilodeau, F.; Gravel, M. Highly Enantioselective Intermolecular Stetter Reactions of β-Aryl Acceptors: α-Ketoester Moiety as Handle for Activation and Synthetic Manipulations. Org. Lett. 2011, 13, 4942–4945; (i) Kim, S. M.; Jin, M. Y.; Kim, M. J.; Cui, Y.; Kim, Y. S.; Zhang, L.; Song, C. E.; Ryu, D. H.; Yang, J. W. N-Heterocyclic Carbene-Catalysed Intermolecular Stetter Reactions of Acetaldehyde. Org. Biomol. Chem. 2011, 9, 2069–2071; (g) Wurz, N. E.; Daniliuc, C. G.; Glorius, F. Highly Enantioselective Intermolecular Stetter Reaction of Simple Acrylates: Synthesis of α-Chiral γ-Ketoesters. Chem. Eur. J. 2012, 18, 16297–16301.
- 39 Nemoto, T.; Fukuda, T.; Hamada, Y. Efficient Synthesis of 3-Substituted 2,3-Dihydroquinolin-4-ones Using a One-Pot Sequential Multi-Catalytic Process: Pd-Catalyzed Allylic Amination-Thiazolium Salt-Catalyzed Stetter Reaction Cascade. Tetrahedron Lett. 2006, 47, 4365–4368
- 40(a) Hong, B.-C.; Dange, N. S.; Hsu, C.-S.; Liao, J.-H. Sequential Organocatalytic Stetter and Michael-Aldol Condensation Reaction: Asymmetric Synthesis of Fully Substituted Cyclopentenes via a [1 + 2 + 2] Annulation Strategy. Org. Lett. 2010, 12, 4812–4815; (b) Hong, B.-C.; Dange, N. S.; Hsu, C.-S.; Liao, J.-H.; Lee, G.-H. Dynamic Kinetic Asymmetric Synthesis of Five Contiguous Stereogenic Centers by Sequential Organocatalytic Stetter and Michael-Aldol Reaction: Enantioselective Synthesis of Fully Substituted Cyclopentanols Bearing a Quaternary Stereocenter. Org. Lett. 2011, 13, 1338–1341.
- 41 Filloux, C. M.; Lathrop, S. P.; Rovis, T. Multicatalytic, Asymmetric Michael/Stetter Reaction of Salicylaldehydes and Activated Alkynes. Proc. Natl. Acad. Sci. 2010, 107, 20666–20671.
- 42 Reddi, Y.; Sunoj, R. B. Asymmetric Dual-Catalytic Cascade by Chiral N-Heterocyclic Carbene and Quinuclidine: Mechanism and Origin of Enantioselectivity in Benzofuranone Formation. ACS Catal. 2015, 5, 1596–1603.
- 43 Cheng, Q.-F.; Wang, J.-W.; Wang, Q.-F.; Liu, Z. Intermolecular Stetter Reaction of Aromatic Aldehydes with (E)-(2-Nitrovinyl)cyclohexane Induced by N-Heterocyclic Carbene and Thiourea. Chin. Chem. Lett. 2016, 27, 1032–1035
- 44
Zhuo, S.; Zhu, T.; Zhou, L.; Mou, C.; Chai, H.; Lu, Y.; Pan, L.; Jin, Z.; Chi, Y. R. Access to All-Carbon Spirocycles through a Carbene and Thiourea Cocatalytic Desymmetrization Cascade Reaction. Angew. Chem. Int. Ed. 2019, 131, 1798–1802
10.1002/ange.201810638 Google Scholar
- 45(a) He, J.; Zheng, J.; Liu, X.; She, X.; Pan, X. N-Heterocyclic Carbene Catalyzed Nucleophilic Substitution Reaction for Construction of Benzopyrones and Benzofuranones. Org. Lett. 2006, 8, 4637−4640; (b) He, J.; Tang, S.; Liu, J.; Su, Y.; Pan, X.; She, X. N-Heterocyclic Carbene Catalyzed Intramolecular Nucleophilic Addition of Carbonyl Anion Equivalents to Enol Ethers. Tetrahedron 2008, 64, 8797− 8800.
- 46 Biju, A. T.; Wurz, N. E.; Glorius, F. N-Heterocyclic Carbene-Catalyzed Cascade Reaction Involving the Hydroacylation of Unactivated Alkynes. J. Am. Chem. Soc. 2010, 132, 5970−5971.
- 47 Zhao, M.; Liu, J.-L.; Liu, H.-F.; Chen, J.; Zhou, L. Construction of Bisbenzopyrone via N-Heterocyclic Carbene Catalyzed Intramolecular Hydroacylation–Stetter Reaction Cascade. Org. Lett. 2018, 20, 2676–2679.
- 48 Biju, A. T., Glorius, F. Intermolecular N-Heterocyclic Carbene Catalyzed Hydroacylation of Arynes. Angew. Chem. Int. Ed. 2010, 49, 9761–9764.
- 49(a) Piel, I.; Steinmetz, M.; Hirano, K.; Fröhlich, R.; Grimme, S.; Glorius, F. Highly Asymmetric NHC-Catalyzed Hydroacylation of Unactivated Alkenes. Angew. Chem. Int. Ed. 2011, 50, 4983−4987; (b) Hirano, K.; Biju, A. T.; Piel, I.; Glorius, F. N-Heterocyclic Carbene- Catalyzed Hydroacylation of Unactivated Double Bonds. J. Am. Chem. Soc. 2009, 131, 14190−14191.
- 50(a) Bugaut, X.; Liu, F.; Glorius, F. N-Heterocyclic Carbene (NHC)-Catalyzed Intermolecular Hydroacylation of Cyclopropenes. J. Am. Chem. Soc. 2011, 133, 8130−8133; (b) Liu, F.; Bugaut, X.; Schedler, M.; Fröhlich, R.; Glorius, F. Designing N-Heterocyclic Carbenes: Simultaneous Enhancement of Reactivity and Enantioselectivity in the Asymmetric Hydroacylation of Cyclopropenes. Angew. Chem. Int. Ed. 2011, 50, 12626−12630.
- 51 Janssen-Müller, D.; Fleige, M.; Schlüns, D.; Wollenburg, M.; Daniliuc, C. G.; Neugebauer, J.; Glorius, F. NHC-Catalyzed Enantioselective Dearomatizing Hydroacylation of Benzofurans and Benzothiophenes for the Synthesis of Spirocycles. ACS Catal. 2016, 6, 5735−5739.
- 52(a) Sohn, S. S.; Rosen, E. L.; Bode, J. W. N-Heterocyclic Carbene- Catalyzed Generation of Homoenolates: γ-Butyrolactones by Direct Annulations of Enals and Aldehydes. J. Am. Chem. Soc. 2004, 126, 14370–14371; (b) Burstein, C.; Glorius, F.; Organocatalyzed Conjugate Umpolung of α,β-Unsaturated Aldehydes for the Synthesis of γ-Butyrolactones. Angew. Chem. Int. Ed. 2004, 43, 6205–6208.
- 53 Burstein, C.; Serena, T.; Xie, X.; Glorius, F. N-Heterocyclic Carbene- Catalyzed Conjugate Umpolung for the Synthesis of γ-Butyrolactones. Synthesis 2006, 2418–2439; (b) Nair, V.; Vellalath, S.; Poonoth, M.; Mohan, R.; Suresh, E. N-Heterocyclic Carbene Catalyzed Reaction of Enals and 1,2-Dicarbonyl Compounds: Stereoselective Synthesis of Spiro γ-Butyrolactones. Org. Lett. 2006, 8, 507–509; (c) Nair, V.; Poonoth, M.; Vellalath, S.; Suresh, E.; Thirumalai, R. An N-Heterocyclic Carbene-Catalyzed [8 + 3] Annulation of Tropone and Enals via Homoenolate. J. Org. Chem. 2006, 71, 8964–8965; (d) Li, Y.; Zhao, Z.-A.; He, H.; You, S.-L. Stereoselective Synthesis of γ-Butyrolactones via Organocatalytic Annulations of Enals and Keto Esters. Adv. Synth. Catal. 2008, 350, 1885–1890; (e) Struble, J. R.; Bode, J. W. Formal Synthesis of Salinosporamide A via NHC-Catalyzed Intramolecular Lactonization. Tetrahedron 2009, 65, 4957–4967.
- 54 Sun, L.-H.; Shen, L.-T.; Ye, S. Highly Diastereo- and Enantioselective NHC-Catalyzed [3+2] Annulation of Enals and Isatins. Chem. Commun. 2011, 47, 10136–10138.
- 55 Ide, R.; Kyan, R.; Le, T. P.; Kitagawa, Y.; Sato, K.; Mase, N.; Narumi, T. Chemoselective Umpolung of Enals for Asymmetric Homoenolate Cross-Annulation of Enals and Aldehydes Catalyzed by N-Heterocyclic Carbene. Org. Lett. 2019, 21, 9119–9123.
- 56 He, M.; Bode, J. W. Catalytic Synthesis of γ-Lactams via Direct Annulations of Enals and N-Sulfonylimines. Org. Lett. 2005, 7, 3131–3134.
- 57(a) Chan, A.; Scheidt, K. A. Highly Stereoselective Formal [3 + 3] Cycloaddition of Enals and Azomethine Imines Catalyzed by N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2007, 129, 5334–5335; (b) Chan, A.; Scheidt, K. A. Direct Amination of Homoenolates Catalyzed by N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2008, 130, 2740–2741; (c) He, M.; Bode, J. W. Enantioselective, NHC-Catalyzed Bicyclo-β- Lactam Formation via Direct Annulations of Enals and Unsaturated N-Sulfonyl Ketimines. J. Am. Chem. Soc. 2008, 130, 418–419; (d) Rommel, M.; Fukuzumi, T.; Bode, J. W. Cyclic Ketimines as Superior Electrophiles for NHC-Catalyzed Homoenolate Additions with Broad Scope and Low Catalyst Loadings. J. Am. Chem. Soc. 2008, 130, 17266–17267; (e) Lv, H.; Tiwari, B.; Mo, J.; Xing, C.; Chi, Y. R. Highly Enantioselective Addition of Enals to Isatin-Derived Ketimines Catalyzed by N-Heterocyclic Carbenes: Synthesis of Spirocyclic γ-Lactams. Org. Lett. 2012, 14, 5412–5415.
- 58 Nair, V.; Vellalath, S.; Poonoth, M.; Suresh, E. N-Heterocyclic Carbene-Catalyzed Reaction of Chalcones and Enals via Homoenolate: An Efficient Synthesis of 1,3,4-Trisubstituted Cyclopentenes. J. Am. Chem. Soc. 2006, 128, 8736–8737.
- 59 Chiang, P.-C.; Kaeobamrung, J.; Bode, J. W. Enantioselective, Cyclopentene-Forming Annulations via NHC-Catalyzed Benzoin-Oxy-Cope Reactions. J. Am. Chem. Soc. 2007, 129, 3520–3521.
- 60(a) Cohen, D. T.; Cardinal-David, B.; Scheidt, K. A. Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N-Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters. Angew. Chem. Int. Ed. 2011, 50, 1678–1682; (b) Guo, C.; Schedler, M.; Daniliuc, C. G.; Glorius, F. N-Heterocyclic Carbene Catalyzed Formal [3+2] Annulation Reaction of Enals: An Efficient Enantioselective Access to Spiro-Heterocycles. Angew. Chem. Int. Ed. 2014, 53, 10232–10236.
- 61(a) Chan, A.; Scheidt, K. A. Conversion of α,β-Unsaturated Aldehydes into Saturated Esters: An Umpolung Reaction Catalyzed by Nucleophilic Carbenes. Org. Lett. 2005, 7, 905–908; (b) Sohn, S. S.; Bode, J. W. Catalytic Generation of Activated Carboxylates from Enals: A Product-Determining Role for the Base. Org. Lett. 2005, 7, 3873–3876.
- 62 Phillips, E. M.; Reynolds, T. E.; Scheidt, K. A. Highly Diastereo- and Enantioselective Additions of Homoenolates to Nitrones Catalyzed by N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2008, 130, 2416–2417.
- 63 Nair, V.; Sinu, C. R.; Babu, B. P.; Varghese, V.; Jose, A.; Suresh, E. Novel Nucleophilic Heterocyclic Carbene Mediated Stereoselective Conjugate Addition of Enals to Nitrostyrenes via Homoenolate. Org. Lett. 2009, 11, 5570–5573.
- 64(a) Maji, B.; Ji, L.; Wang, S.; Vedachalam, S.; Ganguly, R.; Liu, X.-W. N-Heterocyclic Carbene Catalyzed Homoenolate-Addition Reaction of Enals and Nitroalkenes: Asymmetric Synthesis of 5-Carbon-Synthon δ-Nitroesters. Angew. Chem. Int. Ed. 2012, 124, 8401–8405;
10.1002/ange.201203449 Google Scholar(b) White, N. A.; DiRocco, D. A.; Rovis, T. Asymmetric N-Heterocyclic Carbene Catalyzed Addition of Enals to Nitroalkenes: Controlling Stereochemistry via the Homoenolate Reactivity Pathway to Access δ-Lactams. J. Am. Chem. Soc. 2013, 135, 8504–8507.
- 65 Chan, A.; Scheidt, K. A. Conversion of α,β-Unsaturated Aldehydes into Saturated Esters: An Umpolung Reaction Catalyzed by Nucleophilic Carbenes. Org. Lett. 2005, 7, 905–908.
- 66 Zhao, C.; Li, F.; Wang, J. N-Heterocyclic Carbene Catalyzed Dynamic Kinetic Resolution of Pyranones. Angew. Chem. Int. Ed. 2016, 55, 1820–1824.
- 67 Zhang, C.-L.; Han, Y.-F.; Ye, S. N-Heterocyclic Carbene-Catalyzed β-Addition of Enals to 3-Alkylenyloxindoles: Synthesis of Oxindoles with All-Carbon Quaternary Stereocenters. Chem. Commun. 2019, 55, 7966–7969.
- 68 Benoit, C.-D.; Raup, D. E. A.; Scheidt, K. A. Cooperative N-Heterocyclic Carbene/Lewis Acid Catalysis for Highly Stereoselective Annulation Reactions with Homoenolates. J. Am. Chem. Soc. 2010, 132, 5345–5347.
- 69(a) Raup, D. E. A.; Benoit, C.-D.; Holte, D.; Scheidt, K. A. Cooperative Catalysis by Carbenes and Lewis Acids in a Highly Stereoselective Route to γ-Lactams. Nat. Chem. 2010, 2, 766–771;
(b) Cohen, D. T.; Benoit, C.-D.; Scheidt, K. A. Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N-Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters. Angew. Chem. Int. Ed. 2011, 50, 1678–1682;
(c) Julien, D.-T.; O'Bryan, E. A.; Schroeder, T. B. H.; Cohen, D. T.; Scheidt, K. A. An N-Heterocyclic Carbene/Lewis Acid Strategy for the Stereoselective Synthesis of Spirooxindole Lactones. Angew. Chem. Int. Ed. 2012, 124, 5047–5051.
10.1002/ange.201201643 Google Scholar
- 70 Zhao, X.; DiRocco, D. A.; Rovis, T. N-Heterocyclic Carbene and Brønsted Acid Cooperative Catalysis: Asymmetric Synthesis of trans-γ-Lactams. J. Am. Chem. Soc. 2011, 133, 12466–12469.
- 71(a) Wang, M. H.; Cohen, D. T.; Schwamb, C. B.; Mishra, R. K.; Scheidt, K. A. Enantioselective β-Protonation by a Cooperative Catalysis Strategy. J. Am. Chem. Soc. 2015, 137, 5891–5894; (b) Wang, M. H.; Barsoum, D.; Schwamb, C. B.; Cohen, D. T.; Goess, B. C.; Riedrich, M.; Chan, A.; Maki, B. E.; Mishra, R. K.; Scheidt, K. A. Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy. J. Org. Chem. 2017, 82, 4689–4702.
- 72 Guo, C.; Fleige, M.; Janssen-Müller, D.; Daniliuc, C. G.; Glorius, F. Cooperative N-Heterocyclic Carbene/Palladium-Catalyzed Enantioselective Umpolung Annulations. J. Am. Chem. Soc. 2016, 138, 7840–7843.
- 73 Chen, J.; Yuan, P.; Wang, L.; Huang, Y. Enantioselective β-Protonation of Enals via a Shuttling Strategy. J. Am. Chem. Soc. 2017, 139, 7045–7051.
- 74 Zhang, Y.-R.; He, L.; Wu, X.; Shao, P.-L.; Ye, S. Chiral N-Heterocyclic Carbene Catalyzed Staudinger Reaction of Ketenes with Imines: Highly Enantioselective Synthesis of N-Boc β-Lactams. Org. Lett. 2008, 10, 277–280.
- 75 Duguet, N.; Campbell, C. D.; Slawin, A. M. Z.; Smith, A. D. N-Heterocyclic Carbene Catalysed β-Lactam Synthesis. Org. Biomol. Chem. 2008, 6, 1108–1113.
- 76(a) He, L.; Lv, H.; Zhang, Y.-R.; Ye, S. Formal Cycloaddition of Disubstituted Ketenes with 2-Oxoaldehydes Catalyzed by Chiral N-Heterocyclic Carbenes. J. Org. Chem. 2008, 73, 8101–8103; (b) Wang, X.-N.; Shao, P-L.; Lv, H.; Ye, S. Enantioselective Synthesis of β-Trifluoromethyl-β-Lactones via NHC-Catalyzed Ketene−Ketone Cycloaddition Reactions. Org. Lett. 2009, 11, 4029–4031; (c) Wang, T.; Huang, X.-L.; Ye, S. Enantioselective Formal [2+2] Cycloaddition of Ketenes with Nitroso Compounds Catalyzed by N-Heterocyclic Carbenes. Org. Biomol. Chem. 2010, 8, 5007–5011; (d) Huang, X.-L.; Chen, X.-Y.; Ye, S. Enantioselective Synthesis of Aza-β-lactams via NHC-Catalyzed [2 + 2] Cycloaddition of Ketenes with Diazenedicarboxylates. J. Org. Chem. 2009, 74, 7585–7587; (e) Lv, H.; Zhang, Y.-R.; Huang, X.-L.; Ye, S. Asymmetric Dimerization of Disubstituted Ketenes Catalyzed by N-Heterocyclic Carbenes. Adv. Synth. Catal. 2008, 350, 2715–2718.
- 77 Jian, T.-Y.; He, L.; Tang, C.; Ye, S. N-Heterocyclic Carbene Catalysis: Enantioselective Formal [2+2] Cycloaddition of Ketenes and N-Sulfinylanilines. Angew. Chem. Int. Ed. 2011, 50, 9104–9107.
- 78 Wang, X.-N.; Shen, L.-T.; Ye, S. NHC-Catalyzed Enantioselective [2 + 2] and [2 + 2 + 2] Cycloadditions of Ketenes with Isothiocyanates. Org. Lett. 2011, 13, 6382–6385.
- 79(a) Zhang, Y.-R.; Lv, H.; Zhou, D.; Ye, S.; Chiral N-Heterocyclic Carbene-Catalyzed Formal [4+2] Cycloaddition of Ketenes with Enones: Highly Enantioselective Synthesis of trans- and cis-δ-Lactones. Chem. Eur. J. 2008, 14, 8473–8476; (b) Lv, H.; You, L.; Ye, S. Enantioselective Synthesis of Dihydrocoumarins via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and o-Quinone Methides. Adv. Synth. Catal. 2009, 351, 2822–2826; (c) Lv, H.; Chen, X.-Y.; Sun, L.-H.; Ye, S. Enantioselective Synthesis of Indole-Fused Dihydropyranones via Catalytic Cycloaddition of Ketenes and 3-Alkylenyloxindoles. J. Org. Chem. 2010, 75, 6973–6976; (d) Jian, T.-Y.; Chen, X.-Y.; Sun, L.-H.; Ye, S. N-Heterocyclic Carbene-Catalyzed [4 + 2] Cycloaddition of Ketenes and 3-Aroylcoumarins: Highly Enantioselective Synthesis of Dihydrocoumarin-Fused Dihydropyranones. Org. Biomol. Chem. 2013, 11, 158–163; (e) Jian, T.-Y.; Shao, P.-L.; Ye, S. Enantioselective [4+2] Cycloaddition of Ketenes and 1-Azadienes Catalyzed by N-Heterocyclic Carbenes. Chem. Comm. 2011, 47, 2381–2383; (f) Huang, X.-L.; He, L.; Shao, P.-L.; Ye, S. [4+2] Cycloaddition of Ketenes with N-Benzoyldiazenes Catalyzed by N-Heterocyclic Carbenes. Angew. Chem. Int. Ed. 2009, 48, 192–195.
- 80 Shen, L.-T.; Shao, P.-L.; Ye, S. N-Heterocyclic Carbene-Catalyzed Cyclization of Unsaturated Acyl Chlorides and Ketones. Adv. Synth. Catal. 2011, 353, 1943–1948.
- 81(a) Shen, L.-T.; Sun, L.-H.; Ye, S. Highly Enantioselective γ-Amination of α,β-Unsaturated Acyl Chlorides with Azodicarboxylates: Efficient Synthesis of Chiral γ-Amino Acid Derivatives. J. Am. Chem. Soc. 2011, 133, 15894–15897; (b) Shen, L.-T.; Jia, W.-Q.; Ye, S. Catalytic [4+2] Cyclization of α,β-Unsaturated Acyl Chlorides with 3-Alkylenyloxindoles: Highly Diastereo-and Enantioselective Synthesis of Spirocarbocyclic Oxindoles. Angew. Chem. Int. Ed. 2013, 52, 585–588.
- 82 Reynolds, N. T.; Rovis, T. Enantioselective Protonation of Catalytically Generated Chiral Enolates as an Approach to the Synthesis of α-Chloroesters. J. Am. Chem. Soc. 2005, 127, 16406–16407.
- 83 Vora, H. U.; Rovis, T. N-Heterocyclic Carbene Catalyzed Asymmetric Hydration: Direct Synthesis of α-Protio and α-Deuterio α-Chloro and α-Fluoro Carboxylic Acids. J. Am. Chem. Soc. 2010, 132, 2860–2861.
- 84 He, M.; Struble, J. R.; Bode, J. W. Highly Enantioselective Azadiene Diels−Alder Reactions Catalyzed by Chiral N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2006, 128, 8418–8420.
- 85(a) Burstein, C.; Tschan, S.; Xie, X.; Glorius, F. N-Heterocyclic Carbene-Catalyzed Conjugate Umpolung for the Synthesis of γ-Butyrolactones. Synthesis 2006, 14, 2418–2439; (b) Kaeobamrung, J.; Kozlowski, M. C.; Bode, J. W. Chiral N-Heterocyclic Carbene-Catalyzed Generation of Ester Enolate Equivalents from α,β-Unsaturatedaldehydes for Enantioselective Diels–Alder Reactions. Proc. Natl. Acad. Sci. 2010, 107, 20661–20665; (c) Zhao, Y.-M.; Cheung, M. S.; Lin, Z.; Sun, J. Enantioselective Synthesis of β,γ-Unsaturated α-Fluoroesters Catalyzed by N-Heterocyclic Carbenes. Angew. Chem. Int. Ed. 2012, 51, 10359–10363; (d) Xu, J.; Chen, X.; Wang, M.; Zheng, P.; Song, B.-A.; Chi, Y. R. Aminomethylation of Enals through Carbene and Acid Cooperative Catalysis: Concise Access to β2-Amino Acids. Angew. Chem. Int. Ed. 2015, 54, 5161–5165; (e) Wu, Z.; Wang, X.; Li, F.; Wu, J.; Wang, J. Chemoselective N-Heterocyclic Carbene-Catalyzed Cascade of Enals with Nitroalkenes. Org. Lett. 2015, 17, 3588–3591.
- 86(a) Singha, S.; Patea, T.; Daniliuc, C. G.; Glorius, F. Highly Enantioselective [5 + 2] Annulations through Cooperative N-Heterocyclic Carbene (NHC) Organocatalysis and Palladium Catalysis. J. Am. Chem. Soc. 2018, 140, 3551–3554; (b) Zhou, L.; Wu, X.; Yang, X.; Mou, C.; Song, R.; Yu, S.; Chai, H.; Pan, L.; Jin, Z.; Chi, Y. R. Gold and Carbene Relay Catalytic Enantioselective Cycloisomerization/Cyclization Reactions of Ynamides and Enals. Angew. Chem. Int. Ed. 2020, 59, 1557–1561.
- 87 He, M.; Uc, G. J.; Bode, J. W. Chiral N-Heterocyclic Carbene Catalyzed, Enantioselective Oxodiene Diels-Alder Reactions with Low Catalyst Loadings. J. Am. Chem. Soc. 2006, 128, 15088–15089.
- 88 Ni, Q.; Zhang, H.; Grossmann, A.; Loh, C. C. J.; Merkens, C.; Enders, D. Asymmetric Synthesis of Pyrroloindolones by N-Heterocyclic Carbene Catalyzed [2+3] Annulation of α-Chloroaldehydes with Nitrovinylindoles. Angew. Chem. Int. Ed. 2013, 52, 13562–13566.
- 89(a) Zhao, D.; Ruhl, K. E.; Rovis, T. N-Heterocyclic-Carbene-Catalyzed Asymmetric Oxidative Hetero-Diels-Alder Reactions with Simple Aliphatic Aldehydes. Angew. Chem. Int. Ed. 2012, 51, 12330–12333; (b) Mo, J.; Yang, R.; Chen, X.; Tiwari, B.; Chi, Y. R. Direct α-Functionalization of Simple Aldehydes via Oxidative N-Heterocyclic Carbene Catalysis. Org. Lett. 2013, 15, 50–53; (c) Lin, L.; Yang, Y.; Wang, M.; Lai, L.; Guo, Y.; Wang, R. Oxidative N-Heterocyclic Carbene Catalyzed Stereoselective Annulation of Simple Aldehydes and 5-Alkenyl Thiazolones. Chem. Commun, 2015, 51, 8134–8137; (d) Xu, J.; Yuan, S.; Peng, J.; Miao, M.; Chen, Z.; Ren, H. Enantioselective [2+2] Annulation of Simple Aldehydes with Isatin-Derived Ketimines via Oxidative N-Heterocyclic Carbene Catalysis. Chem. Commun. 2017, 53, 3430–3433; (e) Yuan, S.; Luo, Y.; Peng, J.; Miao, M.; Xu, J.; Ren, H. Oxidative Asymmetric [2 + 3] Annulation of Aldehydes with Azomethine Imines Enabled by N-Heterocyclic Carbene Catalysis. Org. Lett. 2017, 19, 6100–6103.
- 90 Mo, J.; Chen, X.; Chi, Y. R. Oxidative γ-Addition of Enals to Trifluoromethyl Ketones: Enantioselectivity Control via Lewis Acid/N- Heterocyclic Carbene Cooperative Catalysis. J. Am. Chem. Soc. 2012, 134, 8810–8813
- 91(a) Lin, Y.; Yang, L.; Deng, Y.; Zhong, G. Cooperative Catalysis of N-Heterocyclic Carbene and Brønsted Acid for a Highly Enantioselective Route to Unprotected Spiro-Indoline-Pyrans. Chem. Commun. 2015, 51, 8330–8333; (b) Rong, X.; Yao, H.; Xia, W.; Du, Y.; Zhou, Y.; Liu, H. Enantioselective Assembly of Spirolactones through NHC-Catalyzed Remote γ-Carbon Addition of Enals with Isatins. ACS Comb. Sci. 2016, 18, 220–224; (c) Wu, Z.; Li, F.; Wang, J. Intermolecular Dynamic Kinetic Resolution Cooperatively Catalyzed by an N-Heterocyclic Carbene and a Lewis Acid. Angew. Chem. Int. Ed. 2015, 54, 1629–1633; (d) Zheng, P.-C.; Cheng, J.; Su, S.; Jin, Z.; Wang, Y.-H.; Yong, S.; Jin, L.-H.; Song, B.-A.; Chi, Y. R. Oxidative N-Heterocyclic Carbene-Catalyzed γ-Carbon Addition of Enals to Imines: Mechanistic Studies and Access to Antimicrobial Compounds. Chem. Eur. J. 2015, 21, 9984–9987; (e) Chen, X.-Y.; Liu, Q.; Chanhan, P.; Peuronoe, A.; Rissanen, K.; Jafari, E.; Enders, D. N-Heterocyclic Carbene Catalyzed [4+2] Annulation of Enals via a Double Vinylogous Michael Addition: Asymmetric Synthesis of 3,5-Diaryl Cyclohexenones. Angew. Chem. Int. Ed. 2017, 56, 6241–6245; (f) Wang, M.; Huang, Z.; Xu, J.; Chi, Y. R. N-Heterocyclic Carbene-Catalyzed [3+4] Cycloaddition and Kinetic Resolution of Azomethine Imines. J. Am. Chem. Soc. 2014, 136, 1214–1217.
- 92 Chen, X.; Yang, S.; Song, B.-A.; Chi, Y. R. Functionalization of Benzylic C(sp3) H Bonds of Heteroaryl Aldehydes through N-Heterocyclic Carbene Organocatalysis. Angew. Chem. Int. Ed. 2013, 52, 11134–11137.
- 93(a) Janssen-Müller, D.; Singha, S.; Olyschläger, T.; Daniliuc, C. G.; Glorius, F. Annulation of o-Quinodimethanes through N-Heterocyclic Carbene Catalysis for the Synthesis of 1-Isochromanones. Org. Lett. 2016, 18, 4444–4447; (b) Chen, D.-F.; Rovis, T. N-Heterocyclic Carbene and Chiral Brønsted Acid Cooperative Catalysis for a Highly Enantioselective [4+2] Annulation. Synthesis 2016, 49, 293–298.
- 94(a) Zhao, Y.-M.; Cheung, M. S.; Lin, Z.; Sun, J. Enantioselective Synthesis of β,γ-Unsaturated α-Fluoroesters Catalyzed by N-Heterocyclic Carbenes. Angew. Chem. Int. Ed. 2012, 51, 10359–10363;
(b) Chen, X.-Y.; Xia, F.; Cheng, J.-T.; Ye, S. Highly Enantioselective γ-Amination by N-Heterocyclic Carbene Catalyzed [4+2] Annulation of Oxidized Enals and Azodicarboxylates. Angew. Chem. Int. Ed. 2013, 125, 10838–10841;
10.1002/ange.201305571 Google Scholar(c) Xiao, Z.; Yu, C.; Li, T.; Wang, X.-S.; Yao, C. N-Heterocyclic Carbene/Lewis Acid Strategy for the Stereoselective Synthesis of Spirocyclic Oxindole-Dihydropyranones. Org. Lett. 2014, 16, 3632–3635; (d) Dong, X.; Sun, J. Catalytic Asymmetric α-Aldol Reaction of Vinylogous N-Heterocyclic Carbene Enolates: Formation of Quaternary and Labile Tertiary Stereocenters. Org. Lett. 2014, 16, 2450–2453; (e) Cheng, J.-T.; Chen, X.-Y.; Gao, Z.-H.; Ye, S. N-Heterocyclic Carbene Catalyzed Generation and [4+2] Annulation of Unsubstituted Dienolate - Enantioselective Synthesis of Spirocyclic Oxindolodihydropyranones. Eur. J. Org. Chem. 2015, 1047–1053; (f) Xiao, Y.; Wang, J.; Xia, W.; Shu, S.; Jiao, S.; Zhou, Y.; Liu, H. γ-Carbon Activation through N-Heterocyclic Carbene/ Brønsted Acids Cooperative Catalysis: A Highly Enantioselective Route to δ-Lactams. Org. Lett. 2015, 17, 3850–3853.
- 95 Zhu, T.; Zheng, P.; Mou, C.; Yang, S.; Chi, Y. R. Benzene Construction via Organocatalytic Formal [3+3] Cycloaddition Reaction. Nat. Commun. 2014, 5, 5027–5033.
- 96 Zeitler, K. Stereoselective Synthesis of (E)-α,β-Unsaturated Esters via Carbene-Catalyzed Redox Esterification. Org. Lett. 2006, 8, 637–640.
- 97 Maki, B. E.; Chan, A.; Phillips, E. M.; Scheidt, K. A. Tandem Oxidation of Allylic and Benzylic Alcohols to Esters Catalyzed by N-Heterocyclic Carbenes. Org. Lett. 2007, 9, 371–374.
- 98 Sarkar, S. D.; Grimme, S.; Studer, A. NHC Catalyzed Oxidations of Aldehydes to Esters: Chemoselective Acylation of Alcohols in Presence of Amines. J. Am. Chem. Soc. 2010, 132, 1190−1191.
- 99 Ryan, S. J.; Candish, L.; Lupton, D. W. N-Heterocyclic Carbene-Catalyzed Generation of α,β-Unsaturated Acyl Imidazoliums: Synthesis of Dihydropyranones by their Reaction with Enolates. J. Am. Chem. Soc. 2009, 131, 14176–14177.
- 100(a) Smrkar, S. D.; Studer, A. NHC-Catalyzed Michael Addition to α,β-Unsaturated Aldehydes by Redox Activation. Angew. Chem. Int. Ed. 2010, 49, 9266–9269; (b) Mo, J.; Shen, L.; Chi, Y. R. Direct β-Activation of Saturated Aldehydes to Formal Michael Acceptors through Oxidative NHC Catalysis. Angew. Chem. Int. Ed. 2013, 52, 8588–8591; (c) Wang, G.; Chen, X.; Miao, G.; Yao, W.; Ma, C. Divergent NHC-Catalyzed Oxidative Transformations of 3-Bromoenal: Selective Synthesis of 2H-Pyran-2-ones and Chiral Dihydropyranones. J. Org. Chem. 2013, 78, 6223–6232; (d) Sun, F.-G.; Sun, L.-H.; Ye, S. N-Heterocyclic Carbene-Catalyzed Enantioselective Annulation of Bromoenal and 1,3-Dicarbonyl Compounds. Adv. Synth. Catal. 2011, 353, 3134–3138; (e) Yao, C.; Wang, D.; Lu, J.; Li, T.; Jiao, W.; Yu, C. N-Heterocyclic Carbene Catalyzed Reactions of α-Bromo- α,β-unsaturated Aldehydes/α,β-Dibromoaldehydes with 1,3-Dinucleophilic Reagents. Chem. Eur. J. 2012, 18, 1914–1917; (f) Yetra, S. R.; Bhunia, A.; Patra, A.; Mane, M. V.; Vanka, K.; Biju, A. T. Enantioselective N-Heterocyclic Carbene-Catalyzed Annulations of 2-Bromoenals with 1,3-Dicarbonyl Compounds and Enamines via Chiral α,β-Unsaturated Acylazoliums. Adv. Synth. Catal. 2013, 355, 1089–1097; (g) Zhu, Z.-Q.; Zheng, X.-L.; Jiang, N.-F.; Wan, X.; Xiao, J.-C. Chiral N-Heterocyclic Carbene Catalyzed Annulation of α,β-Unsaturated Aldehydes with 1,3-Dicarbonyls. Chem. Commun. 2011, 47, 8670–8672.
- 101 Kaeobamrung, J.; Mahatthananchai, J.; Zheng, P.; Bode, J. W. An Enantioselective Claisen Rearrangement Catalyzed by N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2010, 132, 8810–8812.
- 102 Li, G.-T.; Gu, Q.; You, S.-L. Enantioselective Annulation of Enals with 2-Naphthols by Triazolium Salts Derived from L-phenylalanine. Chem. Sci. 2015, 6, 4273–4278.
- 103(a) Xu, J.; Zhang, W.; Liu, Y.; Zhu, S.; Liu, M.; Hua, X.; Chen, S.; Lu, T.; Du, D. Formal [3 + 3] Annulation of Isatin-Derived 2-Bromoenals with 1,3-Dicarbonyl Compounds Enabled by Lewis Acid/N-Heterocyclic Carbene Cooperative Catalysis. RSC Adv. 2016, 6, 18601–18606; (b) Lin, J.-B.; Cheng, X.-N.; Tian, X.-D.; Xu, G.-Q.; Luo, Y.-C.; Xu, P.-F. A C1-Symmetric N-Heterocyclic Carbene Catalysed Oxidative Spiroannulation of Isatin-Derived Enals: Highly Enantioselective Synthesis of Spirooxindole δ-Lactones. RSC Adv. 2018, 8, 15444–15447.
- 104 Biswas, A.; Sarkar, S. D.; Tebben, L.; Studer, A. Enantioselective Cyclopropanation of Enals by Oxidative N-Heterocyclic Carbene Catalysis. Chem. Commun. 2012, 48, 5190–5192.
- 105 Wanner, B.; Mahatthananchai, J.; Bode, J. W. Enantioselective Synthesis of Dihydropyridinones via NHC-Catalyzed Aza-Claisen Reaction. Org. Lett. 2011, 13, 5378–5381.
- 106(a) Kravina, A. G.; Mahatthananchai, J.; Bode, J. W. Enantioselective, NHC-Catalyzed Annulations of Trisubstituted Enals and Cyclic N-Sulfonylimines via α,β-Unsaturated Acyl Azoliums. Angew. Chem. Int. Ed. 2012, 51, 9433–9436; (b) Zhang, H.-M.; Jia, W.-Q.; Liang, Z.-Q.; Ye, S. N-Heterocyclic Carbene-Catalyzed [3+3] Cyclocondensation of Bromoenals and Ketimines: Highly Enantioselective Synthesis of Dihydropyridinones. J. Org. Chem. 2014, 3, 462–465; (c) Enders, D.; Ni, Q.; Xiong, J.; Song, X.; Raabe, G. N-Heterocyclic Carbene Catalyzed Enantioselective Annulation of Benzothiazolyl Ethyl Acetates with 2-Bromoenals. Synlett 2015, 26, 1465–1469; (d) Zhao, L.-L.; Li, X.-S.; Cao, L.-L.; Zhang, R.; Shi, X.-Q.; Qi, J. Access to Dihydropyridinones and Spirooxindoles: Application of N-Heterocyclic Carbene- Catalyzed [3+3] Annulation of Enals and Oxindole-Derived Enals with 2-Aminoacrylates. Chem. Commun. 2017, 53, 5985–5988; (e) Chen, Q.; Zhu, T.; Majhi, P. K.; Mou, C.; Chai, H.; Zhang, J.; Zhuo, S.; Chi, Y. R. Carbene-Catalyzed Enantioselective Oxidative Coupling of Enals and Di(hetero)arylmethanes. Chem. Sci. 2018, 9, 8711–8715; (f) Gao, Z.-H.; Chen, X.-Y.; Zhang, H.-M.; Ye, S. N-Heterocyclic Carbene-Catalyzed [3+3] Cyclocondensation of Bromoenals with Aldimines: Highly Enantioselective Synthesis of Dihydropyridinones. Chem. Commun. 2015, 51, 12040–12043.
- 107 Chen, K.-Q.; Gao, Z.-H.; Ye, S. (Dynamic) Kinetic Resolution of Enamines/Imines: Enantioselective N-Heterocyclic Carbene Catalyzed [3+3] Annulation of Bromoenals and Enamines/Imines. Angew. Chem. Int. Ed. 2019, 58, 1183–1187.
- 108 Chen, K.-Q.; Gao, Z.-H.; Song, C.-Y.; Zhang, C.-L.; Wang, Z.-X.; Ye, S. N-Heterocyclic Carbene Catalyzed Cyclocondensation of α,β-Unsaturated Carboxylic Acids: Enantioselective Synthesis of Pyrrolidinone and Dihydropyridinone Derivative. Angew. Chem. Int. Ed. 2014, 53, 11611–11615.
- 109 Chen, K.-Q.; Li, Y.; Zhang, C.-L.; Sun, D.-Q.; Ye, S. N-Heterocyclic Carbene-Catalyzed [3 + 2] Annulation of Bromoenals with 3-Aminooxindoles: Highly Enantioselective Synthesis of Spirocyclic Oxindolo-γ-lactams. Org. Biomol. Chem. 2016, 14, 2007–2014.
- 110 Wu, X.; Liu, B.; Zhang, Y.; Jeret, M.; Wang, H.; Zheng, P.; Yang, S.; Song, B-A.; Chi, Y. R. Enantioselective Nucleophilic β-Carbon-Atom Amination of Enals: Carbene-Catalyzed Formal [3+2] Reactions. Angew. Chem. Int. Ed. 2016, 55, 12280–12284.
- 111 Zhang, G.; Xu, W.; Liu, J.; Das, D. K.; Yang, S.; Perveen, S.; Zhang, H.; Li, X.; Fang, X. Enantioselective Intermolecular All-Carbon [4+2] Annulation via N-Heterocyclic Carbene Organocatalysis. Chem. Commun. 2017, 53, 13336–13339.
- 112 Perveen, S.; Zhao, Z.; Zhang, G.; Liu, J.; Anwar, M.; Fang, X. Enantioselective Synthesis of 1,2-Dihydronaphthalenes via Oxidative N-Heterocyclic Carbene Catalysis. Org. Lett. 2017, 19, 2470–2473.
- 113 Zhang, C.-L.; Ye, S. N-Heterocyclic Carbene-Catalyzed Construction of 1,3,5-Trisubstituted Benzenes from Bromoenals and α-Cyano-β- methylenones. Org. Lett. 2016, 18, 6408–6411.
- 114 Jia, Q.; Wang, J. N-Heterocyclic Carbene-Catalyzed Convenient Benzonitrile Assembly. Org. Lett. 2016, 18, 2212–2215.
- 115
Wu, S.; Liu, C.; Luo, G.; Jin, Z.; Zheng, P.; Chi, Y. R. NHC-Catalyzed Chemoselective Reactions of Enals and Aminobenzaldehydes for Access to Chiral Dihydroquinolines. Angew. Chem. Int. Ed. 2019, 131, 18581–18584.
10.1002/ange.201909479 Google Scholar
- 116(a) Liang, Z.-Q.; Wang, D.-L.; Zhang, H.-M.; Ye, S. Enantioselective Synthesis of Bicyclic δ-Lactones via N-Heterocyclic Carbene-Catalyzed Cascade Reaction. Org. Lett. 2015, 17, 5140−5143;
(b) Bera, S.; Daniliuc, C. D.; Studer, A. Enantioselective Synthesis of Substituted δ-Lactones by Cooperative Oxidative N-Heterocyclic Carbene and Lewis Acid Catalysis. Org. Lett. 2015, 17, 4940–4943;
(c) Wang, J.; Li, Y.; Wang, H.; Jin, Z.; Chi, Y. R. Carbene-Catalyzed Enantioselective Addition of Benzylic Carbon to Unsaturated Acyl Azolium for Rapid Synthesis of Pyrrolo[3,2-c]quinolones. ACS Catal. 2018, 8, 9859–9864;
(d) Liu, Q.; Chen, X.-Y.; Puttreddy, R.; Rissanen, K.; Enders, D. N-Heterocyclic Carbene Catalyzed Quadruple Domino Reactions: Asymmetric Synthesis of Cyclopenta[c]chromenones. Angew. Chem. Int. Ed. 2018, 130, 17346–17349;
10.1002/ange.201810402 Google Scholar(e) Anwar, M.; Yang, S.; Xu, W.; Liu, J.; Perveen, S.; Kong, X.; Zehra, S. T.; Fang, X. Carbene-Catalyzed Asymmetric Friedel–Crafts Alkylation-Annulation Sequence and Rapid Synthesis of Indole-Fused Polycyclic Alkaloids. Commun. Chem. 2019, 2, 85.
- 117 Hao, L.; Du, Y.; Lv, H.; Chen, X.; Jiang, H.; Shao, Y.; Chi, Y. R. Enantioselective Activation of Stable Carboxylate Esters as Enolate Equivalents via N-Heterocyclic Carbene Catalysts. Org. Lett. 2012, 14, 2154–2157.
- 118 Hao, L.; Chen, S.; Xu, J.; Tiwari, B.; Fu, Z.; Li, T.; Lim, J.; Chi, Y. R. Organocatalytic Activation of Alkylacetic Esters as Enolate Precursors to React with α,β-Unsaturated Imines. Org. Lett. 2013, 15, 4956–4959.
- 119 Chen, S.; Hao, L.; Zhang, Y.; Chi, Y. R. Asymmetric Access to the Smallest Enolate Intermediate via Organocatalytic Activation of Acetic Ester. Org. Lett. 2013, 15, 5822–5825.
- 120 Chen, X.; Fong, J. Z. M.; Xu, J.; Mou, C.; Song, Y.; Chi, Y. R. Carbene- Catalyzed Dynamic Kinetic Resolution of Carboxylic Esters. J. Am. Chem. Soc. 2016, 138, 7212–7215.
- 121 Lee, A.; Younai, A.; Price, C. K.; Izquierdo, J.; Mishra, R. K.; Scheidt, K. A. Enantioselective Annulations for Dihydroquinolones by in situ Generation of Azolium Enolates. J. Am. Chem. Soc. 2014, 136, 10589–10592.
- 122 Fu, Z.; Xu, J.; Zhu, T.; Leong, W. W. Y.; Chi, Y. R. β-Carbon Activation of Saturated Carboxylic Esters Through N-Heterocyclic Carbene Organocatalysis. Nat. Chem. 2013, 5, 835–839.
- 123 Fu, Z.; Jiang, K.; Zhu, T.; Torres, J.; Chi, Y. R. Access to Oxoquinoline Heterocycles via N-Heterocyclic Carbene-Catalyzed Ester Activation and Selective Domino Reaction. Angew. Chem. Int. Ed. 2014, 53, 6506–6510.
- 124 Xu, J.; Yuan, S.; Miao, M.; Chen, Z. 1-Hydroxybenzotriazole-Assisted, N-Heterocyclic Carbene Catalyzed β-Functionalization of Saturated Carboxylic Esters: Access to Spirooxindole Lactones. J. Org. Chem. 2016, 81, 11454–11460.
- 125 Jin, Z.; Chen, S.; Wang, Y.; Zheng, P.; Yang, S.; Chi, Y. R. β-Functionalization of Carboxylic Anhydrides with β-Alkyl Substituents through Carbene Organocatalysis. Angew. Chem. Int. Ed. 2014, 53, 13506–13509.
- 126 Jin, Z.; Fu, Z.; Jiang, K.; Torres, J.; Zheng, P.; Yang, S.; Song, B.-A.; Chi, Y. R. Nucleophilic β-Carbon Activation of Propionic Acid as a 3-Carbon Synthon by Carbene Organocatalysis. Chem. Eur. J. 2015, 21, 9360–9363.
- 127 Xie, Y.; Yu, C.; Li, T.; Tu, S.; Yao, C. An NHC-Catalyzed in Situ Activation Strategy to β-Functionalize Saturated Carboxylic Acid: An Enantioselective Formal [3+2] Annulation for Spirocyclic Oxindolo-λ-butyrolactones. Chem. Eur. J. 2015, 21, 5355–5359.
- 128 Chen, J.; Huang, Z.; Chi, Y. R. NHC Organocatalytic LUMO Activation of α,β-Unsaturated Esters to React with Enamides. Angew. Chem. Int. Ed. 2013, 52, 8592–8596.
- 129 Fu, Z.; Wu, X.; Chi, Y. R. Rapid Access to Bicyclic δ-Lactones via Carbene-Catalyzed Activation and Cascade Reaction of Unsaturated Carboxylic Esters. Org. Chem. Front. 2016, 3, 145–149.
- 130 Mou, C.; Wu, J.; Huang, Z.; Sun, J.; Jin, Z.; Chi, Y. R. Carbene-Catalyzed LUMO Activation of Alkyne Esters for Access to Functional Pyridines. Chem. Commun. 2017, 53, 13359–13362.
- 131 Liu, B.; Wang, W.; Huang, R.; Yan, J.; Wu, J.; Xue, W.; Yang, S.; Jin, Z.; Chi, Y. R. Direct Activation of β-sp3-Carbons of Saturated Carboxylic Esters as Electrophilic Carbons via Oxidative Carbene Catalysis. Org. Lett. 2018, 20, 260–263.
- 132 Zhang, Z.; Zeng, X.; Xie, D.; Chen, D.; Ding, L.; Wang, A.; Yang, L.; Zhong, G. N-Heterocyclic Carbene-Catalyzed Activation of Esters of N-Hydroxyphthalimide: A Highly Enantioselective Route to Chiral Dihydropyridinones Bearing an All Carbon Quaternary Stereogenic Center. Org. Lett. 2015, 17, 5052–5055.
- 133 Chen, X.-Y.; Gao, Z.-H.; Song, C.-Y.; Zhang, C.-L.; Wang, Z.-X.; Ye, S. N-Heterocyclic Carbene Catalyzed Cyclocondensation of α,β-Unsaturated Carboxylic Acids: Enantioselective Synthesis of Pyrrolidinone and Dihydropyridinone Derivatives. Angew. Chem. Int. Ed. 2014, 53, 11611–11615.
- 134 Xu, J.; Jin, Z.; Chi, Y. R. Organocatalytic Enantioselective γ-Aminoalkylation of Unsaturated Ester: Access to Pipecolic Acid Derivatives. Org. Lett. 2013, 15, 5028–5031.
- 135 Xu, J.; Yuan, S.; Miao, M. N-Heterocyclic Carbene Catalyzed [4 + 2] Annulation Reactions with in situ Generated Heterocyclic ortho- Quinodimethanes. Org. Lett. 2016, 18, 3822–3825.
- 136 Que, Y.; Li, T.; Yu, C.; Wang, X.-S.; Yao, C. Enantioselective Assembly of Spirocyclic Oxindole-dihydropyranones through NHC-Catalyzed Cascade Reaction of Isatins with N-Hydroxybenzotriazole Esters of α,β-Unsaturated Carboxylic Acid. J. Org. Chem. 2015, 80, 3289–3294.
- 137 Jia, W.-Q.; Zhang, H.-M.; Zhang, C.-L.; Gao, Z.-H.; Ye, S. N-Heterocyclic Carbene-Catalyzed [4 + 2] Annulation of α,β-Unsaturated Carboxylic Acids: Enantioselective Synthesis of Dihydropyridinones and Spirocyclic Oxindolodihydropyridinones. Org. Chem. Front. 2016, 3, 77–81.
- 138 Fang, S.; Jin, S. Ma, R.; Lu, T.; Du, D. Asymmetric Synthesis of C2-Quaternary Indolin-3-ones Enabled by N-Heterocyclic Carbene Catalysis. Org. Lett. 2019, 21, 5211–5214.
- 139 Que, Y.; Xie, Y.; Li, T.; Yu, C.; Tu, S.; Yao, C. An N-Heterocyclic Carbene-Catalyzed Oxidative γ-Aminoalkylation of Saturated Carboxylic Acids through in Situ Activation Strategy: Access to δ-Lactam. Org. Lett. 2015, 17, 6234–6237.
- 140 Mansoorabadi, S. O.; Seravalli, J.; Furdui, C.; Krymov, V.; Gerfen, G. J.; Begley, T. P.; Melnick, J.; Ragsdale, S. W.; Reed, G. H. EPR Spectroscopic and Computational Characterization of the Hydroxyethylidene-Thiamine Pyrophosphate Radical Intermediate of Pyruvate: Ferredoxin Oxidoreductase. Biochemistry 2006, 45, 7122–7131.
- 141 Chabrière, E., Vernède, X., Guigliarelli, B., Charon, M.-H.; Hatchikian, E. C.; Fontecilla-Camps, J. C. Crystal Structure of the Free Radical Intermediate of Pyruvate: Ferredoxin Oxidoreductase. Science 2010, 294, 2559–256.
- 142(a) Rehbein, J.; Ruser, S. M.; Phan, J. NHC-Catalysed Benzoin Condensation-Is It All Down to the Breslow Intermediate? Chem. Sci. 2015, 6, 6013–6018; (b) Phan, J.; Ruser, S. M.; Zeitler, K.; Rehbein, J. NHC-Stabilized Radicals in the Formal Hydroacylation Reaction of Alkynes. Eur. J. Org. Chem. 2019, 557–561.
- 143 Regnier, V.; Romero, E. A.; Molton, F.; Jazzar, R.; Bertrand, G.; Martin, D. What Are the Radical Intermediates in Oxidative N-Heterocyclic Carbene Organocatalysis? J. Am. Chem. Soc. 2019, 141, 1109–1117.
- 144 Guin, J.; Sarkar, S. D.; Grimme, S.; Studer, A. Biomimetic Carbene- Catalyzed Oxidations of Aldehydes Using TEMPO. Angew. Chem. Int. Ed. 2008, 47, 8727–8730.
- 145 Du, Y.; Wang, Y.; Li, X.; Shao, Y.; Li, G.; Webster, R. D.; Chi, Y. R. N-Heterocyclic Carbene Organocatalytic Reductive β,β-Coupling Reactions of Nitroalkenes via Radical Intermediates. Org. Lett. 2014, 16, 5678–5681.
- 146 Li, B.-S.; Wang, Y.; Proctor, R. S. J.; Zhang, Y.; Webster, R. D.; Yang, S.; Song, B.; Chi, Y. R. Carbene-Catalysed Reductive Coupling of Nitrobenzyl Bromides and Activated Ketones or Imines via Single- Electron-Transfer Process. Nat. Commun. 2016, 7, 12933.
- 147 Wang, Y.; Du, Y.; Huang, X.; Wu, X.; Zhang, Y.; Yang, S.; Chi, Y. R. Carbene-Catalyzed Reductive Coupling of Nitrobenzyl Bromide and Nitroalkene via the Single-Electron-Transfer (SET) Process and Formal 1,4-Addition. Org. Lett. 2017, 19, 632–635.
- 148 White, N. A.; Rovis, T. Enantioselective N-Heterocyclic Carbene- Catalyzed β-Hydroxylation of Enals Using Nitroarenes: An Atom Transfer Reaction That Proceeds via Single Electron Transfer. J. Am. Chem. Soc. 2014, 136, 14674–14677.
- 149 Zhang, Y.; Du, Y.; Huang, Z.; Xu, J.; Wu, X.; Wang, Y.; Wang, M.; Yang, S.; Webster, R. D.; Chi, Y. R. N-Heterocyclic Carbene-Catalyzed Radical Reactions for Highly Enantioselective β-Hydroxylation of Enals. J. Am. Chem. Soc. 2015, 137, 2416–2419.
- 150 Wang, H.; Wang, Y.; Chen, X.; Mou, C.; Yu, S.; Chai, H.; Jin, Z.; Chi, Y. R. Chiral Nitroarenes as Enantioselective Single-Electron-Transfer Oxidants for Carbene-Catalyzed Radical Reactions. Org. Lett. 2019, 21, 7440–7444.
- 151 White, N. A.; Rovis, T. Oxidatively Initiated NHC-Catalyzed Enantioselective Synthesis of 3,4-Disubstituted Cyclopentanones from Enals. J. Am. Chem. Soc. 2015, 137, 10112–10115.
- 152 Yang, W.; Hu, W.; Dong, X.; Li, X.; Sun, J. N-Heterocyclic Carbene Catalyzed ϒ-Dihalomethylenation of Enals by Single-Electron Transfer. Angew. Chem. Int. Ed. 2016, 55, 15783–15786.
- 153 Wu, X.; Zhang, Y.; Wang, Y.; Ke, J.; Jeret, M.; Reddi, R. N.; Yang, S.; Song, B-A.; Chi, Y. R. Polyhalides as Efficient and Mild Oxidants for Oxidative Carbene Organocatalysis by Radical Processes. Angew. Chem. Int. Ed. 2017, 56, 2942–2946.
- 154 Che, X.-Y.; Chen, K.-Q.; Sun, D.-Q.; Ye, S. N-Heterocyclic Carbene- Catalyzed Oxidative [3 + 2] Annulation of Dioxindoles and Enals: Cross Coupling of Homoenolate and Enolate. Chem. Sci. 2017, 8, 1936–1941.
- 155 Ishii, T.; Kakeno, Y.; Nagao, K.; Ohmiya, H. N-Heterocyclic Carbene- Catalyzed Decarboxylative Alkylation of Aldehydes. J. Am. Chem. Soc. 2019, 141, 3854–3858.
- 156 Ishii, T.; Ota, K.; Nagao, K.; Ohmiya, H. N-Heterocyclic Carbene- Catalyzed Radical Relay Enabling Vicinal Alkylacylation of Alkenes. J. Am. Chem. Soc. 2019, 141, 14073–14077.
- 157(a) Li, J.-L.; Liu, Y.-Q.; Zou, W.-L.; Zeng, R.; Zhang, X.; Liu, Y.; Han, B.; He, Y.; Leng, H.-J.; Li, Q.-Z. Radical Acylfluoroalkylation of Olefins through N-Heterocyclic Carbene Organocatalysis. Angew. Chem. Int. Ed. 2020, 59, 1863–1870; (b) Zhang, B.; Peng, Q.; Guo, D.; Wang, J. NHC-Catalyzed Radical Trifluoromethylation Enabled by Togni Reagent. Org. Lett. 2020, 22, 443–447.
- 158 DiRocco, D. A.; Rovis, T. Catalytic Asymmetric α-Acylation of Tertiary Amines Mediated by a Dual Catalysis Mode: N-Heterocyclic Carbene and Photoredox Catalysis. J. Am. Chem. Soc. 2012, 134, 8094–8097.
- 159 Dai, L.; Xia, Z.-H.; Gao, Y.-Y.; Gao, Z.-H.; Ye, S. Visible-Light-Driven N-Heterocyclic Carbene Catalyzed ϒ-and ε-Alkylation with Alkyl Radicals. Angew. Chem. Int. Ed. 2019, 58, 18124–18130.
- 160 Dai, L.; Ye, S. Photo/N-Heterocyclic Carbene Co-catalyzed Ring Opening and ϒ-Alkylation of Cyclopropane Enal. Org. Lett. 2020, 22, 986–990.
- 161 Mavroskoufis, A.; Rajes, K.; Golz, P.; Agrawal, A.; Ruß, V. T.; Götze, J. P.; Hopkinson, M. N. N-Heterocyclic Carbene Catalyzed Photoenolization/Diels-Alder Reaction of Acid Fluorides. Angew. Chem. Int. Ed. 2020, 59, 3190–3194.
- 162 Fischer, C.; Smith, S. W.; Powell, D. A.; Fu, G. C. Umpolung of Michael Acceptors Catalyzed by N-Heterocyclic Carbenes. J. Am. Chem. Soc. 2006, 128, 1472−1473.
- 163 He, L.; Jian, T.-Y.; Ye, S. N-Heterocyclic Carbene Catalyzed Aza-Morita−Baylis−Hillman Reaction of Cyclic Enones with NTosylarylimines. J. Org. Chem. 2007, 72, 7466−7468.
- 164 Chen, X.-Y.; Xia, F.; Ye, S. Catalytic MBH Reaction of β-Substituted Nitroalkenes with Azodicarboxylates. Org. Biomol. Chem. 2013, 11, 5722−5726.
- 165 Atienza, R. L.; Roth, H. S.; Scheidt, K. A. N-Heterocyclic Carbene- Catalyzed Rearrangements of Vinyl Sulfones. Chem. Sci. 2011, 1772−1776.
- 166(a) Matsuoka, S.-I.; Ota, Y.; Washio, A.; Katada, A.; Ichioka, K.; Takagi, K.; Suzuki, M. Organocatalytic Tail-to-Tail Dimerization of Olefin: Umpolung of Methyl Methacrylate Mediated by NHeterocyclic Carbene. Org. Lett. 2011, 13, 3722−3725; (b) Biju, A. T.; Padmanaban, M.; Wurz, N. E.; Glorius, F. N-Heterocyclic Carbene Catalyzed Umpolung of Michael Acceptors for intermolecular Reactions. Angew. Chem. Int. Ed. 2011, 50, 8412−8415.
- 167 Patra, A.; Mukherjee, S.; Das, T. K.; Jain, S.; Gonnade, R. G.; Biju, A. T. N-Heterocyclic-Carbene-Catalyzed Umpolung of Imines. Angew. Chem. Int. Ed. 2017, 56, 2730 –2734.
- 168 Das, T. K.; Ghosh, A.; Balanna, K.; Behera, P.; Gonnade, R. G.; Marelli, U. K.; Das, A. K.; Biju, A. T. N-Heterocyclic Carbene-Catalyzed Umpolung of Imines for the Enantioselective Synthesis of Dihydroquinoxalines. ACS Catal. 2019, 9, 4065−4071.