Mechanistic Investigation, Wavelength-Dependent Reactivity, and Expanded Reactivity of N–Aryl Azacycle Photomediated Ring Contractions

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(8), С. 5580 - 5596

Опубликована: Фев. 12, 2024

Under mild blue-light irradiation, α-acylated saturated heterocycles undergo a photomediated one-atom ring contraction that extrudes heteroatom from the cyclic core. However, for nitrogenous heterocycles, this powerful skeletal edit has been limited to substrates bearing electron-withdrawing substituents on nitrogen. Moreover, mechanism and wavelength-dependent efficiency of transformation have remained unclear. In work, we increased electron richness nitrogen in azacycles improve light absorption strengthen critical intramolecular hydrogen bonding while enabling direct installation photoreactive handle. As result, broadly expanded substrate scope, including underexplored electron-rich previously unsuccessful now achieved. The significantly improved yields diastereoselectivities facilitated reaction rate, kinetic isotope effect (KIE), quenching studies, addition determination quantum yields. Guided by these propose revised ET/PT contraction, which is additionally corroborated computational characterization lowest-energy excited states through time-dependent DFT. at wavelengths longer than those strongly absorbed was investigated rate measurements, revealed red shift photochemical action plot relative absorbance. elucidated mechanistic photophysical details effectively rationalize empirical observations, additive effects, were poorly understood. Our findings not only demonstrate enhanced synthetic utility shed but may also offer valuable guidance understanding reactivity related systems.

Язык: Английский

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Photocatalytic Decarboxylative Alkylation of Cyclic Imine–BF₃ Complexes: A Modular Route to Functionalized Azacycles

Journal of the American Chemical Society, Год журнала: 2024, Номер unknown

Опубликована: Сен. 12, 2024

Alkyl radicals generated via an acridine photocatalyzed decarboxylation reaction of feedstock carboxylic acids engage with a range cyclic imine-BF

Язык: Английский

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Alicyclic‐Amine‐Derived Imine‐BF₃ Complexes: Easy‐to‐Make Building Blocks for the Synthesis of Valuable α‐Functionalized Azacycles

Angewandte Chemie International Edition, Год журнала: 2023, Номер 63(1)

Опубликована: Ноя. 1, 2023

A new strategy to access α-functionalized alicyclic amines via their corresponding imine-BF

Язык: Английский

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The Αrt of Decorating Piperidine Scaffold into Alkaloid Precursors

Tetrahedron, Год журнала: 2025, Номер unknown, С. 134606 - 134606

Опубликована: Март 1, 2025

Язык: Английский

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Palladium‐Catalyzed Arylation of Endocyclic 1‐Azaallyl Anions: Concise Synthesis of Unprotected Enantioenriched cis‐2,3‐Diarylpiperidines

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(36)

Опубликована: Июль 18, 2023

Unprotected cis-2,3-diarylpiperidines are synthesized through an unprecedented palladium-catalyzed cross-coupling reaction between aryl halides and elusive endocyclic 1-azaallyl anions. These intermediates generated in situ by the deprotonation of 2-aryl-1-piperideines, precursors that readily prepared two operations from simple piperidines. An asymmetric version this with (2R, 3R)-iPr-BI-DIME as ligand provides products moderate to good yields enantioselectivities. This study significantly expands synthetic utility

Язык: Английский

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Annulation of O-silyl N,O-ketene acetals with alkynes for the synthesis of dihydropyridinones and its application in concise total synthesis of phenanthroindolizidine alkaloids

Frontiers in Chemistry, Год журнала: 2023, Номер 11

Опубликована: Сен. 21, 2023

The formation of N -heterocycles with multiple substituents is important in organic synthesis. Herein, we report a novel method for the construction functionalized dihydropyridinone rings through annulation an amide α -carbon tethered alkyne moiety. reaction was achieved via O -silyl , -ketene acetal and silver-mediated addition. Furthermore, developed applied total synthesis phenanthroindolizidine phenanthroquinolizidine alkaloids. By varying coupling partners, concise collective these alkaloids achieved.

Язык: Английский

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Palladium-Catalyzed Allylation of Endocyclic 1-Azaallyl Anions

The Journal of Organic Chemistry, Год журнала: 2024, Номер 89(12), С. 8896 - 8905

Опубликована: Июнь 10, 2024

Endocyclic 1-azaallyl anions engage allyl acetates in a palladium-catalyzed allylation followed by reduction to give unprotected 2-(hetero)aryl-3-allylpiperidines and 2-allyl-3-arylmorpholines, products not easily accessible other means. The group is then readily transformed into variety of functional groups. Preliminary studies on the asymmetric variant reaction using an enantiomerically pure BI-DIME-type ligand provide product with moderate enantioselectivity. Computational suggest that energy barriers inner-sphere reductive elimination outer-sphere nucleophilic substitution are almost same, which makes both them possible pathways. In addition, mechanism displays enantiodiscriminating C–C bond forming step, while much less selective, combined

Язык: Английский

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Regioselective α-Phosphonylation of Unprotected Alicyclic Amines

Organic Letters, Год журнала: 2024, Номер 26(28), С. 5972 - 5977

Опубликована: Июль 5, 2024

Unprotected alicyclic amines undergo α-C-H bond phosphonylation via a two-stage one-pot process involving the oxidation of amine-derived lithium amides with simple ketone oxidants, generating transient imines which are then captured phosphites or phosphine oxides. Amines an existing α-substituent regioselective α'-phosphonylation. Amine α-arylation and α'-phosphonylation can be combined, difunctionalized product in single operation.

Язык: Английский

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Acridine/Lewis Acid Complexes as Powerful Photocatalysts: A Combined Experimental and Mechanistic Study

ACS Catalysis, Год журнала: 2024, Номер 14(19), С. 14574 - 14585

Опубликована: Сен. 16, 2024

A class of in-situ generated Lewis acid (LA) activated acridine complexes is reported, which act as potent photochemical catalysts for the oxidation a variety protected secondary amines. Acridine/LA exhibit tunable excited state reduction potentials ranging from +2.07 to 2.38 V vs. SCE. The ytterbium triflate complex 3,6-di-t-butyl-9-mesitylacridine catalyzes Giese-type reaction Boc-protected amines with challenging conjugate acceptors such acrylates, that are inaccessible analogous acridinium (t-Bu-Mes-Acr⊕) catalyzed reaction. mechanism this was investigated using suite physical organic probes including intramolecular 13C kinetic isotope effects (KIEs), variable time normalization analysis (VTNA) kinetics, determination redox potentials, and computational studies. In by t-Bu-Mes-Acr⊕, mechanistic studies consistent single-electron transfer (SET) ground-state reduced t-Bu-Mes-Acr• α-keto radical intermediate first irreversible step in catalytic cycle. Intriguingly, we find acridine/LA better ground reductants (-0.72 -0.74 vs SCE) relative (-0.59 predict increased substrate reactivity stems lower energy barrier key SET event.

Язык: Английский

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Alicyclic‐Amine‐Derived Imine‐BF₃ Complexes: Easy‐to‐Make Building Blocks for the Synthesis of Valuable α‐Functionalized Azacycles

Angewandte Chemie, Год журнала: 2023, Номер 136(1)

Опубликована: Ноя. 1, 2023

Abstract A new strategy to access α‐functionalized alicyclic amines via their corresponding imine‐BF 3 complexes is reported. Isolable complexes, readily prepared dehydrohalogenation of N ‐bromoamines in a base‐promoted/18‐crown‐6 catalyzed process followed by addition boron trifluoride etherate, undergo reactions with wide range organometallic nucleophiles afford azacycles. Organozinc and organomagnesium add at ambient temperatures, obviating the need for cryogenic conditions. In situ preparation provides morpholines piperazines directly from parent single operation. α‐Functionalized can be elaborated further, instance installing second substituent α′‐position.

Язык: Английский

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