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Review
. 2021 Mar 8;27(14):4478-4499.
doi: 10.1002/chem.202003923. Epub 2021 Jan 18.

BIAN-NHC Ligands in Transition-Metal-Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N-Heterocyclic Carbenes?

Changpeng Chen  1 , Feng-Shou Liu  1   2 , Michal Szostak  1
Affiliations
Review

BIAN-NHC Ligands in Transition-Metal-Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N-Heterocyclic Carbenes?

Changpeng Chen et al. Chemistry. .

Abstract

The discovery of NHCs (NHC = N-heterocyclic carbenes) as ancillary ligands in transition-metal-catalysis ranks as one of the most important developments in synthesis and catalysis. It is now well-recognized that the strong σ-donating properties of NHCs along with the ease of scaffold modification and a steric shielding of the N-wingtip substituents around the metal center enable dramatic improvements in catalytic processes, including the discovery of reactions that are not possible using other ancillary ligands. In this context, although the classical NHCs based on imidazolylidene and imidazolinylidene ring systems are now well-established, recently tremendous progress has been made in the development and catalytic applications of BIAN-NHC (BIAN = bis(imino)acenaphthene) class of ligands. The enhanced reactivity of BIAN-NHCs is a direct result of the combination of electronic and steric properties that collectively allow for a major expansion of the scope of catalytic processes that can be accomplished using NHCs. BIAN-NHC ligands take advantage of (1) the stronger σ-donation, (2) lower lying LUMO orbitals, (3) the presence of an extended π-system, (4) the rigid backbone that pushes the N-wingtip substituents closer to the metal center by buttressing effect, thus resulting in a significantly improved control of the catalytic center and enhanced air-stability of BIAN-NHC-metal complexes at low oxidation state. Acenaphthoquinone as a precursor enables facile scaffold modification, including for the first time the high yielding synthesis of unsymmetrical NHCs with unique catalytic properties. Overall, this results in a highly attractive, easily accessible class of ligands that bring major advances and emerge as a leading practical alternative to classical NHCs in various aspects of catalysis, cross-coupling and C-H activation endeavors.

Keywords: N-heterocyclic carbenes; carbenes; homogeneous catalysis; ligand classes; transition metals.

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Figures

Figure 1.
Figure 1.
Structures of Classical NHC Ligands.
Figure 2.
Figure 2.
Structural Features of BIAN-NHC Ligands and their Impact on Catalysis.
Figure 3.
Figure 3.
Structures of the Most Common BIAN–NHC Ligands in Transition-Metal-Catalysis.
Scheme 1.
Scheme 1.
Heck Cross-Coupling of Aryl Bromides Catalyzed by in Situ Formed BIAN–NHC–Pd or Preformed (BIAN–NHC)2PdCl2 Reported by Çetinkaya.
Scheme 2.
Scheme 2.
Suzuki Cross-Coupling of Aryl Chlorides and Aryl Bromides Catalyzed by BIAN–NHC–Pd Reported by Green.
Scheme 3.
Scheme 3.
Synthesis of Sterically-Hindered Biaryls by Suzuki Cross-Coupling of Aryl Chlorides and Bromides Cata-lyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 4.
Scheme 4.
Suzuki Cross-Coupling of Aryl Bromides Catalyzed by BIAN–NHC–Pd Reported by Peris.
Scheme 5.
Scheme 5.
Suzuki Cross-Coupling of Aryl Halides Catalyzed by BIAN–NHC–Pd Reported by Humphrey.
Scheme 6.
Scheme 6.
Suzuki Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd in Air Reported by Liu.
Scheme 7.
Scheme 7.
Suzuki Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd in Air Reported by Liu.
Scheme 8.
Scheme 8.
Suzuki Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd in Air Reported by Liu.
Scheme 9.
Scheme 9.
Suzuki Cross-Coupling of 9-Chloroacridine Catalyzed by Nanoparticles supported BIAN–NHC–Pd Reported by Tu.
Scheme 10.
Scheme 10.
Negishi Cross-Coupling of Aryl Chlorides and Bro-mides Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 11.
Scheme 11.
Sonogashira Cross-Coupling of Aryl Halides Catalyzed by BIAN–NHC–Pd/NHC–Cu Reported by Tu.
Scheme 12.
Scheme 12.
Murahashi Cross-Coupling of Aryl Bromides Cata-lyzed by BIAN–NHC–Pd Reported by Feringa and Organ.
Scheme 13.
Scheme 13.
Direct C–H Arylation of Azoles with Aryl Bromides Catalyzed by BIAN–NHC–Pd in Air Reported by Liu.
Scheme 14.
Scheme 14.
Acylation of Aryl Halides with Hydrocinnamaldehyde Catalyzed by BIAN–NHC–Pd Reported by Peris.
Scheme 15.
Scheme 15.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides and Bromides Catalyzed by BIAN–NHC–Pd Reported by Green.
Scheme 16.
Scheme 16.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 17.
Scheme 17.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 18.
Scheme 18.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by Unsymmetrical BIAN–NHC–Pd in Air Reported by Liu.
Scheme 19.
Scheme 19.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by Bulky BIAN–IPent–Pd in Air Reported by Liu.
Scheme 20.
Scheme 20.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by Bulky BIAN–IPr*MeO–Pd in Air Reported by Liu.
Scheme 21.
Scheme 21.
Buchwald-Hartwig Cross-Coupling of Aryl Chlorides Catalyzed by BIAN–NHC–Pd Reported by Bazzi.
Scheme 22.
Scheme 22.
Aminocarbonylation of Aryl Iodides Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 23.
Scheme 23.
Double Aminocarbonylation of o-Diiodobenzene Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 24.
Scheme 24.
Direct Alkylsulfonylation of Aryl Boronic Acids with Alkyl Halides Catalyzed by BIAN–NHC–Pd Reported by Tu.
Scheme 25.
Scheme 25.
Enantioselective C–H Alkylation of Fluoroarenes Catalyzed by BIAN–NHC–Ni Reported by Shi.
Scheme 26.
Scheme 26.
Enantioselective C–H Annulation of Pyridones Catalyzed by BIAN–NHC–Ni Reported by Cramer.
Scheme 27.
Scheme 27.
[3+2] Cross-Dimerization of Olefins and Methylenecyclpropanes Catalyzed by BIAN–NHC–Ni Reported by Ho.
Scheme 28.
Scheme 28.
Reductive Coupling between Imines and Alkynes Catalyzed by BIAN–NHC–Ni Reported by Ye.
Scheme 29.
Scheme 29.
Buchwald-Hartwig Cross-Coupling of Aryl Tosylates Catalyzed by BIAN–NHC–Ni Reported by Tu.
Scheme 30.
Scheme 30.
Hydroformylation of 1-Octene Catalyzed by BIAN–NHC–Rh Reported by Green.
Scheme 31.
Scheme 31.
β-Alkylation 1-Phenylethanol with 1° Alcohols Cata-lyzed by Pyrene–NHC–Ir Reported by Peris.
Scheme 32.
Scheme 32.
H/D Exchange Catalyzed by Pyrene–NHC–Ir Report-ed by Peris.
Scheme 33.
Scheme 33.
Ring Closing Metathesis Catalyzed by BIAN–NHC–Ru Reported by Merino.
Scheme 34.
Scheme 34.
Ring Closing Metathesis Catalyzed by BIAN–NHC–Ru Reported by Bazzi.
Scheme 35.
Scheme 35.
C–H Arylation of 2-Arylpyridines Catalyzed by Py-rene–NHC–Ru Reported by Peris.
Scheme 36.
Scheme 36.
C–H Hydroarylation of Alkenes Catalyzed by Pyrene–NHC–Ru Reported by Peris.
Scheme 37.
Scheme 37.
Direct Alkylsulfonylation of Aryl Boronic Acids with Alkyl Halides Catalyzed by BIAN–NHC–Au Reported by Tu.
Scheme 38.
Scheme 38.
Direct Arylsulfonylation of Aryl Boronic Acids with Diaryliodonium Salts Catalyzed by BIAN–NHC–Au Reported by Tu.
Scheme 39.
Scheme 39.
Hydroamination of Phenylacetylene Catalyzed by Pyrene–NHC–Au Reported by Peris.
Scheme 40.
Scheme 40.
Electrophilic 1-En-6-yne Cyclization Catalyzed by BIAN–NHC–Au Reported by Plenio.
Scheme 41.
Scheme 41.
Enantioselective Protoboration of α-Olefins Catalyzed BIAN–NHC–Cu Reported by Shi.
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