Organocatalysis Using N-Heterocyclic Carbenes (NHCs)

Catalysis is a fundamentally sustainable process, which can be used to produce a wide range of chemicals and their intermediates. Among the various catalytic methods, N-heterocyclic carbene (NHC)-catalyzed umpolung (reversal of inherent polarity) of aldehydes is widely used for the unconventional access to target molecules.[1] Moreover, NHC-catalysis is known for umpolung of Michael acceptors, but imine umpolung is unknown in this realm of catalysis. In this context, we have recently demonstrated, for the first time, the NHC-catalyzed umpolung of imines for the synthesis of 2,3-disubstituted indoles, functionalized quinolines and dihydroquinoxalines.[2] Moreover, we have utilized the aldehyde umpolung strategy for the NHC-catalyzed atroposelective synthesis of N-aryl succinimides having an axially chiral C-N bond via the desymmetrization of N-aryl maleimides (see the Scheme).[3] Moreover, we have demonstrated the NHC-catalyzed umpolung of Michael acceptors for the activated olefin–isatin cross-coupling.[4] The details of these works will be discussed.[5]. The details of these works will be presented.

References:

1.For reviews, see: (a) Flanigan, D. M.; Romanov-Michailidis, F.; White, N. A. Rovis, T. Chem. Rev. 2015, 115, 9307. (b) Biju, A. T. N-Heterocyclic Carbenes in Organocatalysis; Wiley-VCH Verlag GmbH & Co. KGa A: Boschstr. 12, 69469 Weinheim, Germany, 2019.
2.(a) Patra, A.; Mukherjee, S.; Das, T. K.; Jain, S.; Gonnade, R. G.; Biju, A. T. Angew. Chem., Int. Ed. 2017, 56, 2730. (b) Patra, A.; Gelat, F.; Pannecoucke, X.; Poisson, T.; Besset. T.; Biju, A. T. Org. Lett. 2018, 20, 1086. (c) (c) Das, T. K.; Ghosh, A.; Balanna, K.; Behera, P.; Gonnade, R. G.; Marelli, U. K.; Das, A. K.; Biju, A. T. ACS Catal. 2019, 9, 4065.
3.(a) Barik, S.; Shee, S.; Das, S.; Gonnade, R. G.; Jindal, G.; Mukherjee, S.; Biju, A. T. Angew. Chem. Int. Ed. 2021, 60, 12264. (b) Barik, S.; Das, R. C.; Balanna, K.; Biju, A. T. Org. Lett. 2022, 24, 5456.
4.Barik, S.; Shee, S.; Biju, A. T. Org. Lett. 2022, 24, 6066.
5.Mondal, S.; Yetra, S. R.; Mukherjee, S. Biju, A. T. Acc. Chem. Res. 2019, 52, 425.