Photochemically induced reactions of selected ketones with 4‐cyanopyridine in neutral and acidic medium

Bernardi, R.; Caronna, Tullio; Morrocchi, S.; Ursini, Maurizio

doi:10.1002/jhet.5570330422

Cited by 17 publications

(4 citation statements)

References 17 publications

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“…An early reaction including cyanoarenes as arylation reagents was presented in 1975 by Vittimberga ( Figure 17). [81] By reacting cyanopyridine 61 and benzophenone under irradiation in am ixture of isopropanol and sulfuric acid, carbinol 62 and benzhydrylpyridine 63 were formed in moderate yields. Although not preparatively useful, the feasibility of such radical arylations with cyanoarenes was documented.…”

Section: Cyanoarenesmentioning

confidence: 99%

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The Persistent Radical Effect in Organic Synthesis

2019

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Radical–radical couplings are mostly nearly diffusion‐controlled processes. Therefore, the selective cross‐coupling of two different radicals is challenging and not a synthetically valuable transformation. However, if the radicals have different lifetimes and if they are generated at equal rates, cross‐coupling will become the dominant process. This high cross‐selectivity is based on a kinetic phenomenon called the persistent radical effect (PRE). In this Review, an explanation of the PRE supported by simulations of simple model systems is provided. Radical stabilities are discussed within the context of their lifetimes, and various examples of PRE‐mediated radical–radical couplings in synthesis are summarized. It is shown that the PRE is not restricted to the coupling of a persistent with a transient radical. If one coupling partner is longer‐lived than the other transient radical, the PRE operates and high cross‐selectivity is achieved. This important point expands the scope of PRE‐mediated radical chemistry. The Review is divided into two parts, namely 1) the coupling of persistent or longer‐lived organic radicals and 2) “radical–metal crossover reactions”; here, metal‐centered radical species and more generally longer‐lived transition‐metal complexes that are able to react with radicals are discussed—a field that has flourished recently.

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Section: Cyanoarenesmentioning

confidence: 99%

“…b) Electron-transfer-induced reaction of benzophenone with 4-cyanopyridine. [81,82] Figure 18. a) Arylation of alkanes under photochemical conditions.…”

Section: Cyanoarenesmentioning

confidence: 99%

The Persistent Radical Effect in Organic Synthesis

2019

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“…Early work on the photochemistry of cyanopyridines centered on radical substitution reactions in which the cyanide group was substituted for an alkyl group derived from a ketone (e.g., benzophenone), − alcohol, , or olefin coupling partner. These methods employed UV light to photoexcite either the cyanopyridine (λ max = 281 nm for 2,4-dicyanopyridine) or the ketone component (in the case of benzophenone).…”

Section: Reductive Transformations Of Heteroarenes Through Photochemi...mentioning

confidence: 99%

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

et al. 2021

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We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner’s guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N–H, O–H, S–H, and C–H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X=Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.

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“…IR/cm −1 (ATR): 3027, 1682, 1596, 1449, 1413, 1181, 992, 752, 701. 1 35 1,4-Diphenyl-4-(pyridine-2-yl)butan-1-one (6b). Following general procedure A, (phenyl)-[2-phenylcyclopropyl]methanone (0.30 mmol, 66.6 mg, 1.00 equiv) and 2-cyanopyridine (0.39 mmol, 37.6 μL, 1.30 equiv) were irradiated for 48 h at room temperature.…”

Section: H H-2′ + H-6′ + H-2″-3″ + H-5″-6″ Major; H-2′ + H-6′mentioning

confidence: 99%

Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp³)–H Arylation and Cyclopentene Synthesis through Strain Release

et al. 2021

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A metal-free Hantzsch ester-mediated synthesis of cyclopentenylketones as well as γ-hetarylketones starting from ketocyclopropanes under eco-friendly conditions was developed. The versatility of the developed conditions is shown by reacting ketocyclopropanes in both a formal [3 + 2] cycloaddition with terminal alkynes (further investigated using theoretical calculations) and a radical C−C-coupling with cyanopyridines. The newly developed methodologies were later on utilized as a downstream reaction for photogenerated cyclopropanes combining UV and visible light photochemistry. Following this procedure, a UV-driven Norrish−Yang-type reaction induces the ring strain of the intermediates, which serves as activation energy for the subsequent ring transformation.

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Photochemically induced reactions of selected ketones with 4‐cyanopyridine in neutral and acidic medium

Abstract: The presence of the 4‐cyanopyridine, in neutral or acidic medium, interferes with the normal behavior of the biradicals obtained by direct excitation of selected ketones, and results in formation of pyridinic derivatives.

Cited by 17 publications

References 17 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp³)–H Arylation and Cyclopentene Synthesis through Strain Release

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Photochemically induced reactions of selected ketones with 4‐cyanopyridine in neutral and acidic medium

Abstract: The presence of the 4‐cyanopyridine, in neutral or acidic medium, interferes with the normal behavior of the biradicals obtained by direct excitation of selected ketones, and results in formation of pyridinic derivatives.

Cited by 17 publications

References 17 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp3)–H Arylation and Cyclopentene Synthesis through Strain Release

Contact Info

Product

Resources

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Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp³)–H Arylation and Cyclopentene Synthesis through Strain Release