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Evidence for Simultaneous Dearomatization of Two Aromatic Rings under Mild Conditions in Cu(I)-Catalyzed Direct Asymmetric Dearomatization of Pyridine
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nihms-1692066.pdf
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Accepted version
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5.51 MB
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63a35d601da4649dec2fa06a84b1fc7c
Author(s) • •
Gribble, Michael W
Liu, Richard Y
Buchwald, Stephen L
Date Issued
2020
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Citation
Gribble, Michael W, Liu, Richard Y and Buchwald, Stephen L. 2020. "Evidence for Simultaneous Dearomatization of Two Aromatic Rings under Mild Conditions in Cu(I)-Catalyzed Direct Asymmetric Dearomatization of Pyridine." Journal of the American Chemical Society, 142 (25).
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Author's final manuscript
Abstract
© 2020 American Chemical Society. Bis(phosphine) copper hydride complexes are uniquely able to catalyze direct dearomatization of unactivated pyridines with carbon nucleophiles, but the mechanistic basis for this result has been unclear. Here we show that, contrary to our initial hypotheses, the catalytic mechanism is monometallic and proceeds via dearomative rearrangement of the phenethylcopper nucleophile to a Cpara-metalated form prior to reaction at heterocycle C4. Our studies support an unexpected heterocycle-promoted pathway for this net 1,5-Cu-migration beginning with a doubly dearomative imidoyl-Cu-ene reaction. Kinetics, substituent effects, computational modeling, and spectroscopic studies support the involvement of this unusual process. In this pathway, the CuL2 fragment subsequently mediates a stepwise Cope rearrangement of the doubly dearomatized intermediate to the give the C4-functionalized 1,4-dihydropyridine, lowering a second barrier that would otherwise prohibit efficient asymmetric catalysis.
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DOI of Published Version
10.1021/JACS.0C04486