Transition-Metal-Free Intermolecular α-Arylation of Ketones via Enolonium Species

Maksymenko, Shimon; Parida, Keshaba Nanda; Pathe, Gulab Khushalrao; More, Atul A.; Lipisa, Yuriy B.; Szpilman, Alex M.

doi:10.1021/acs.orglett.7b03064

Cited by 50 publications

(24 citation statements)

References 47 publications

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“…Among them, those involving diaryliodonium salts provide a good synthetic alternative. [5] Elegant methods based on the triflic acid-mediated hydrative arylation of alkynes, [6] or the reaction of electron-rich aromatic compounds with in-situ generated enolonium species (umpolung reactivity), [7] have also been developed. Aryldiazonium salts are ideal starting materials in organic synthesis because they can be prepared in one step from cost-effective anilines, [8] and can be easily reduced ( º ~ + 0 V vs Ag/AgCl) [9] to the corresponding highly reactive aryl radical.…”

Section: Introductionmentioning

confidence: 99%

Salicylic Acid‐Catalyzed Arylation of Enol Acetates with Anilines

Felipe‐Blanco

González-Gómez

2018

Adv Synth Catal

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α-Aryl ketones are both structure moieties commonly found in bioactive compounds and versatile synthetic intermediates for the preparation of drug-like molecules. An operationally simple and scalable protocol has been developed to prepare α-aryl ketones from readily available aromatic amines and enol acetates (or silyl enol ethers). This metal-free methodology features the use of salicylic acid as a convenient catalyst to promote the formation of aryl radicals from in-situ generated aryl diazonium salts, without demanding thermal or photochemical activation. The mild reaction conditions used are compatible with anilines substituted with diverse functionalities. Structural elaboration of some prepared α-aryl ketones was accomplished to illustrate their usefulness as building blocks.

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Section: Introductionmentioning

confidence: 99%

Salicylic Acid‐Catalyzed Arylation of Enol Acetates with Anilines

Felipe‐Blanco

González-Gómez

2018

Adv Synth Catal

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“…In contrast, reversing the order of addition of the TMS-enol ethers afforded 13 in 68% yield. It should be noted that we have previously used the enolonium species 4 (R 1 = p- I-C 6 H 4 , R 2 = H) successfully in the coupling with 2-methylindole and N -methyl-2-methylindole and obtained the products in 77% and 74% yield, respectively [ 32 ]. The low yield achieved here therefore reflects issues unique to the reaction with the second enolate and not the stability of the enolonium species itself.…”

Section: Resultsmentioning

confidence: 99%

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

Parida¹,

Pathe²,

Maksymenko³

et al. 2018

Beilstein J. Org. Chem.

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Due to their closely matched reactivity, the coupling of two dissimilar ketone enolates to form a 1,4-diketone remains a challenge in organic synthesis. We herein report that umpolung of a ketone trimethylsilyl enol ether (1 equiv) to form a discrete enolonium species, followed by addition of as little as 1.2–1.4 equivalents of a second trimethylsilyl enol ether, provides an attractive solution to this problem. A wide array of enolates may be used to form the 1,4-diketone products in 38 to 74% yield. Due to the use of two TMS enol ethers as precursors, an optimization of the cross-coupling should include investigating the order of addition.

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“…Prior to and following these advances, useful transition‐metal‐free α‐arylation processes have been developed that involve stoichiometric reactions of enolate anions (or equivalents) with electrophilic aromatic derivatives of Bi V , Pb IV , I(III), S(IV), or benzyne . Stepwise methods via initial formation of N ‐alkoxyenamines or enolonium equivalents followed by nucleophilic attack have also been used for the α‐arylation of ketones …”

Section: Methodsmentioning

confidence: 99%