Organic Synthesis Using Nitroxides

Chemical Reviews, Год журнала: 2023, Номер 123(16), С. 10302 - 10380

Опубликована: Авг. 14, 2023

Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R1R2N–O•. The spin distribution over nitroxide N and O atoms contributes to thermodynamic stability of these radicals. presence bulky N-substituents R1 R2 prevents radical dimerization, ensuring their kinetic stability. Despite reactivity toward various transient C some nitroxides can be easily stored under air at room temperature. Furthermore, oxidized oxoammonium salts (R1R2N═O+) reduced anions (R1R2N–O–), enabling them act valuable oxidants reductants depending on oxidation state. Therefore, they exhibit interesting across all three states. Due fascinating properties, find extensive applications in diverse fields such biochemistry, medicinal chemistry, materials science, organic synthesis. This review focuses versatile For use other important fields, we will refer several articles. introductory part provides a brief overview history chemistry. Subsequently, key methods for preparing discussed, followed by an examination structural diversity physical properties. main portion this is dedicated reactions, wherein parent corresponding serve active species. It demonstrated that functional groups (such alcohols, amines, enolates, alkanes among others) efficiently oxidized. These oxidations carried out using catalysts combination stoichiometric terminal oxidants. By reducing anions, become effective reagents intriguing Nitroxides possess ability selectively react making useful terminating cascade reactions forming alkoxyamines. Depending structure, alkoxyamines weak C–O bonds, allowing thermal generation through reversible bond cleavage. Such thermally generated participate transformations, discussed end review. application strategy natural product synthesis presented.

Язык: Английский

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N-Heterocyclic Carbene-Catalyzed Imine Umpolung/Semipinacol Rearrangement Cascade for the Synthesis of Indoxyls

ACS Catalysis, Год журнала: 2024, Номер 14(6), С. 4202 - 4210

Опубликована: Март 4, 2024

Aldimine umpolung using N-heterocyclic carbenes (NHCs) is less explored compared to the well-known polarity reversal of aldehydes. Described herein NHC-catalyzed aldimine umpolung/semipinacol rearrangement cascade for atom- and pot-economic synthesis fluorescent active, N–H unprotected indoxyl derivatives. Moreover, conditions are identified enantioselective α-iminols by aldimines. The nucleophilic aza-Breslow intermediates intercepted with carbonyl electrophiles. Preliminary DFT studies shed light on rearomative proton transfer coupled aryl migration in an ortho-quinonemethide intermediate facilitating semipinacol rearrangement. In addition, antibacterial activity synthesized indoxyls has been evaluated.

Язык: Английский

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Photoredox Asymmetric Nucleophilic Dearomatization of Indoles with Neutral Radicals

ACS Catalysis, Год журнала: 2021, Номер 11(2), С. 998 - 1007

Опубликована: Янв. 6, 2021

The dearomatization of indoles represents the most efficient approach for accessing highly valued indolines. inherent nucleophilic reactivity has dictated indole development in both 1e– and 2e– processes. However, electron-deficient been challenging. Herein, we introduce a conceptually distinct photoredox-mediated Giese-type transformation strategy, which is generally used conjugate addition radicals to simple α, β-unsaturated systems, chemoselectively breaking C═C bonds embedded aromatic structure. Moreover, diastereoselective challenging neutral achieved by Oppolzer camphorsultam chiral auxiliary. Structurally diverse amine-functionalized indolines carrying functional stereochemical diversity are produced from wide array amines as radical precursors. Furthermore, mild, powerful manifold capable late-stage modification complex natural products pharmaceuticals. DFT studies performed elucidate observed outcomes.

Язык: Английский

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Steering the antitumor drug discovery campaign towards structurally diverse indolines

Bioorganic Chemistry, Год журнала: 2019, Номер 94, С. 103436 - 103436

Опубликована: Ноя. 13, 2019

Язык: Английский

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Organocatalytic Asymmetric Dearomative Oxyalkylation of Indoles Enables Access to C2-Quaternary Indolin-3-ones

Organic Letters, Год журнала: 2019, Номер 21(14), С. 5626 - 5629

Опубликована: Июль 5, 2019

A facile and efficient asymmetric dearomative oxyalkylation of indoles with TEMPO oxoammonium salt a variety aldehydes ketones has been described. This metal-free approach provides straightforward access to C2 quaternary oxindoles in high yields excellent diastereo- enantioselectivities under very mild conditions. The reaction goes smoothly even only 0.1% equivalent catalyst. Moreover, 2-alkylindoles have proven be suitable substrates for the first time.

Язык: Английский

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A general approach to 2,2-disubstituted indoxyls: total synthesis of brevianamide A and trigonoliimine C

Chemical Science, Год журнала: 2021, Номер 12(41), С. 13756 - 13763

Опубликована: Янв. 1, 2021

A general, user-friendly approach to 2,2-disubstituted indoxyls is presented. The method particularly useful for the preparation of 2,2-dialkylindoxyl products, and applied concise total syntheses brevianamide trigonoliimine C.

Язык: Английский

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Electrochemical Oxidative Addition of Nucleophiles on 2-Arylindoles: Synthesis of C2-Heteroquaternary Indolin-3-ones

The Journal of Organic Chemistry, Год журнала: 2022, Номер 87(23), С. 15771 - 15782

Опубликована: Ноя. 17, 2022

An electrochemical method has been developed to synthesize 2,2-disubstituted indolin-3-ones under mild conditions. A series of nucleophiles have added the 2-arylindole-3-ones, generated in situ metal-free oxidative dearomatization 2-arylindoles, afford 3-carbonyl indoles with heteroquaternary centers 57-79% yields.

Язык: Английский

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Organocatalyzed Enantioselective Aza-Morita–Baylis–Hillman Reaction of Cyclic Ketimine with α,β-Unsaturated γ-Butyrolactam

The Journal of Organic Chemistry, Год журнала: 2023, Номер 88(11), С. 6599 - 6610

Опубликована: Май 8, 2023

The enantioselective aza-MBH reaction is an efficient strategy for constructing novel carbon-carbon bonds, providing access to multitudinous chiral densely functionalized MBH products. However, the of cyclic-ketimines that would generate a versatile synthon still missing and challenging. Herein, we developed challenging direct organocatalytic asymmetric involving cyclic ketimines attached neutral functional group. Moreover, α,β-unsaturated γ-butyrolactam was utilized as rare nucleophile alkene in this work. reactions provide enantiomerically enriched 2-alkenyl-2-phenyl-1,2-dihydro-3H-indol-3-ones, bearing with tetra-substituted stereogenic center. features high α-selectivities, enantioselectivities (up 99% ee), good yields 80%).

Язык: Английский

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Combining photoredox catalysis and hydrogen atom transfer for dearomative functionalization of electron rich heteroarenes

Chemical Science, Год журнала: 2023, Номер 14(12), С. 3332 - 3337

Опубликована: Янв. 1, 2023

Engineering organophotoredox catalysis with hydrogen atom transfer directs toward an unfavorable dearomatization process under mild reaction conditions.

Язык: Английский

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Dearomative ipso-Cyclization to Spiropseudoindoxyls: An Extendable Approach To Access Indolo[3,2-c]quinolinones and Isocryptolepine

Organic Letters, Год журнала: 2023, Номер 26(1), С. 68 - 72

Опубликована: Дек. 31, 2023

A metal-free oxidative intramolecular dearomative spirocyclization of indole-3-formyl-2-carboxamides has been developed for the first time, affording spiropseudoindoxyls in good yields. This domino process proceeds through sequential oxidation, decarboxylation and ipso-arylation. The unique feature this approach includes compatibility N-protected-indole-2-carboxamides. Further, a hitherto unknown rearrangement to indoloquinolones achieved. synthetic utility strategy also showcased by construction natural alkaloid, isocryptolepine.

Язык: Английский

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