Enantioselective Hydrodifluoroalkylation of Alkenes with Conformationally Tuned Peptidyl Hydrogen Atom Transfer Catalysts

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Март 20, 2025

We report the enantioselective hydrodifluoroalkylation of alkenes proceeding via an asymmetric hydrogen atom transfer (HAT) event catalyzed by thiol-containing tetrapeptides. Photocatalytic generation a difluoroacetyl radical followed carbon–carbon bond formation results in prochiral carbon-centered that engages with chiral catalyst. A trialkylamine reductant is proposed to turn over catalyst this net-reductive transformation. Notably, incorporating (S)-β-methyl-substituted cysteine as N-terminal residue improved selectivity relative native (Cys) residue, and X-ray crystallographic analysis supports conformational underpinning effect. range enantioenriched γ-substituted amides were synthesized up 96:4 enantiomeric ratio, demonstrating broad functional group tolerance method. Models accounting for induction are supporting DFT calculations.

Язык: Английский

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Visible Light-Promoted Deracemization of α-Amino Aldehyde by Synergistic Chiral Primary Amine and Hypervalent Iodine Catalysis

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Фев. 6, 2025

α-Amino aldehydes, as versatile chiral synthons, are easily racemized under normal acid or base conditions, seriously limiting their synthetic potentials. We report herein an effective deracemization of α-amino aldehydes by a synergistic primary amine and hypervalent iodine catalysis visible light. The developed catalytic system allows for the on-demand production α-Boc- Cbz-protected amino with high enantioselectivity. Mechanistic studies verified photochemical Z-E isomerization mechanism that drives process.

Язык: Английский

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Stereochemical Editing at sp³-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer

Accounts of Chemical Research, Год журнала: 2025, Номер unknown

Опубликована: Фев. 19, 2025

ConspectusMillions of chiral compounds contain a stereogenic sp3-hybridized carbon center with hydrogen atom as one the four different substituents. The can be edited in an increasing number cases by selective transfer (HAT) to and from photocatalyst. This Account describes development photochemical deracemization reactions using oxazole-annulated benzophenones bonding motif that allows them recognize lactam substrates two-point bonding. backbone catalysts consists azabicyclo[3.3.1]nonan-2-one U-shaped geometry, which enables substrate recognition occur parallel benzoxazole part aromatic ketones. photocatalysts facilitate catalytic several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, 4,7-diaza-1-isoindolinones. In addition, if more than is present, editing delivers distinct diastereoisomer upon appropriate selection respective photocatalyst enantiomer. operate via benzophenone triplet selectively abstracts properly positioned exclusively two enantiomers. step creates planar carbon-centered radical erases absolute configuration at this position. While returning HAT same position would likely recreate configuration, spectroscopic quantum chemical studies suggest delivered heteroatom conjugation center. Two scenarios distinguished for shuttling process. For 4,7-diaza-1-isoindolinones, back occurs carbonyl oxygen or imine-type nitrogen not involved binding catalyst. oxindoles single group available accept atom. It currently assumed group, although comparison former reaction pathway, latter process appears less efficient prone side reactions. both cases, achiral enol enamine formed, dissociation catalyst statistically either stereoisomers substrate. Since only enantiomer (or diastereoisomer) processed, high enantioselectivity diastereoselectivity) results. Even though contra-thermodynamic process, described decoupling thermal usage loadings vary between 2.5 10 mol % depending on specific mode action.

Язык: Английский

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Photocatalyst-Dependent Enantioselectivity in the Light-Driven Deracemization of Cyclic α-Aryl Ketones

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Апрель 22, 2025

We report a photoredox-enabled deracemization of cyclic α-aryl ketones that occurs with high stereoselectivity and yield proceeds by mechanistically distinct proton transfer reactions. This reaction is jointly mediated visible-light photocatalyst chiral phosphate base cocatalyst under blue light irradiation. Notably, the extent for this exhibits an unexpected dependence on identity concentration cocatalyst, wherein can be increased employing photocatalysts more positive ground-state reduction potentials, raising or combination these factors. effect attributed to two competing processes, back-electron deprotonation, which consume same intermediate, we propose kinetic model rationalizes behavior. also demonstrate redox properties impact product-forming step, dominant stereoselective step in transformation. Together, mechanistic insights facilitate deeper understanding complexity light-driven reactions involving reversible electron suggest approaches processes may increased.

Язык: Английский

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Aromatic Deformylative Deuteration Enabled by Cobalt–Photocatalysis at Ambient Temperature

ACS Catalysis, Год журнала: 2025, Номер unknown, С. 8522 - 8529

Опубликована: Май 6, 2025

Язык: Английский

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Photoredox-mediated cobalt catalysis for non-asymmetric and asymmetric synthesis

Cell Reports Physical Science, Год журнала: 2025, Номер unknown, С. 102613 - 102613

Опубликована: Май 1, 2025

Язык: Английский

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