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Well-defined, air- and moisture-stable palladium-imidazo[1,5-]pyridin-3-ylidene complexes: a versatile catalyst platform for cross-coupling reactions by L-shaped NHC ligands
We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5- a ]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. These precatalysts feature fast activation to monoligated Pd(0) with 1 : 1 Pd to ligand ratio in a rigid imidazo[1,5- a...
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Published in: | Catalysis science & technology 2022-10, Vol.12 (21), p.6581-6589 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5-
a
]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. These precatalysts feature fast activation to monoligated Pd(0) with 1 : 1 Pd to ligand ratio in a rigid imidazo[1,5-
a
]pyridin-3-ylidene template. Steric matching of the C5-substituent and N2-wingtip in the catalytic pocket of the catalyst framework led to the discovery of ImPyMesDipp as a highly reactive imidazo[1,5-
a
]pyridin-3-ylidene ligand for Pd-catalyzed cross-coupling of nitroarenes by challenging C-NO
2
activation. Kinetic studies demonstrate fast activation and high reactivity of this class of well-defined ImPy-Pd catalysts. Structural studies provide full characteristics of this new class of imidazo[1,5-
a
]pyridin-3-ylidene ligands. Computational studies establish electronic properties of sterically-restricted imidazo[1,5-
a
]pyridin-3-ylidene ligands. Finally, a scalable synthesis of C5-substituted imidazo[1,5-
a
]pyridin-3-ylidene ligands through Ni-catalyzed Kumada cross-coupling is disclosed. The method obviates chromatographic purification at any of the steps, resulting in a facile and modular access to ImPy ligands. We anticipate that well-defined [Pd-ImPy] complexes will find broad utility in organic synthesis and catalysis for activation of unreactive bonds.
We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5-
a
]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. |
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ISSN: | 2044-4753 2044-4761 |
DOI: | 10.1039/d2cy01136k |