We report a general, highly selective method for Suzuki–Miyaura cross-coupling of N-acylphthalimides via N–C(O) acyl cleavage catalyzed by Pd–PEPPSI-type precatalysts. Of broad synthetic interest, the method introduces N-acylphthalimides as new, bench-stable, highly reactive, twist-controlled, amide-based precursors to acyl-metal intermediates. The reaction delivers functionalized biaryl ketones by acylative Suzuki–Miyaura cross-coupling with readily available boronic acids. Studies demonstrate that cheap, easily prepared, and broadly applicable Pd–PEPPSI-type precatalysts supported by a sterically demanding IPr (1,3-Bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) ancillary ligand provide high yields in this reaction. Preliminary selectivity studies and the effect of Pd–N-heterocyclic carbenes (NHC) complexes with allyl-type throw-away ligands are described. We expect that N-acylphthalimides will find significant use as amide-based acyl coupling reagents and cross-coupling precursors to acyl-metal intermediates.
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Well-defined, air- and moisture-stable palladium–imidazo[1,5- a ]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 ]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.
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- Award ID(s):
- 1650766
- NSF-PAR ID:
- 10412443
- Date Published:
- Journal Name:
- Catalysis Science & Technology
- Volume:
- 12
- Issue:
- 21
- ISSN:
- 2044-4753
- Page Range / eLocation ID:
- 6581 to 6589
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2CY01136K
